draft-ietf-mpls-lsp-ping-07.txt   draft-ietf-mpls-lsp-ping-08.txt 
Network Working Group K. Kompella Network Working Group Kireeti Kompella
Internet Draft Juniper Networks Internet Draft Juniper Networks, Inc.
Category: Standards Track G. Swallow Category: Standards Track
Expires: April 2005 Cisco Systems Expiration Date: August 2005
October 2004 George Swallow
Cisco Systems, Inc.
February 2005
Detecting MPLS Data Plane Failures Detecting MPLS Data Plane Failures
draft-ietf-mpls-lsp-ping-07.txt
*** DRAFT *** draft-ietf-mpls-lsp-ping-08.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, I certify that any applicable By submitting this Internet-Draft, the authors certify that any
patent or other IPR claims of which I am aware have been disclosed, applicable patent or other IPR claims of which we are aware have been
and any of which I become aware will be disclosed, in accordance with disclosed, and any of which we become aware will be disclosed, in
RFC 3668. accordance with RFC 3668.
Internet-Drafts are working documents of the Internet Engineering This document is an Internet-Draft and is in full conformance with
Task Force (IETF), its areas, and its working groups. Note that all provisions of Section 5 of RFC3667. Internet-Drafts are working
other groups may also distribute working documents as Internet- documents of the Internet Engineering Task Force (IETF), its areas,
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2005).
Abstract Abstract
This document describes a simple and efficient mechanism that can be This document describes a simple and efficient mechanism that can be
used to detect data plane failures in Multi-Protocol Label Switching used to detect data plane failures in Multi-Protocol Label Switching
(MPLS) Label Switched Paths (LSPs). There are two parts to this (MPLS) Label Switched Paths (LSPs). There are two parts to this
document: information carried in an MPLS "echo request" and "echo document: information carried in an MPLS "echo request" and "echo
reply" for the purposes of fault detection and isolation; and reply" for the purposes of fault detection and isolation; and
mechanisms for reliably sending the echo reply. mechanisms for reliably sending the echo reply.
Changes since last revision Changes since last revision
(This section to be removed before publication.) (This section to be removed before publication.)
Added a new error code for Downstream Mapping Mismatch. o added clarification of TLV lengths, with examples;
o added a Global Flags field in the header for the
Split TLV space into "mandatory" and "optional"; updated IANA 'validate FEC' flag;
allocation policies to reflect this. o fixed the optional vs. mandatory Types wording;
o added several new FEC sub-TLVs:
- 12 BGP labeled IPv4 prefix
+ 12 BGP labeled IPv4 prefix
+ 13 BGP labeled IPv6 prefix (TBD)
+ 14 Generic IPv4 prefix
+ 15 Generic IPv6 prefix
+ 16 Nil FEC
o in Downstream Mapping TLV
+ added an Address Type of IPv6 Unnumbered;
+ added DS Flags to the DS Map, with 2 defined bits;
+ renamed Hash key type to multipath type and dropped
codepoints for which no processing rules have been
defined;
o added "Reply TOS byte" TLV;
o updated processing rules to deal fully deal with implicit
null labels
o added text on processing fewer prefixes in DS maps;
o added text on "Testing LSPs That Are Used to Carry MPLS
Payloads";
o fixed text on non-compatible routers.
Added two new top-level TLVs for LSR Self Test. Contents
Added a new optional top-level TLV for "Errored TLVs" 1 Introduction .............................................. 5
1.1 Conventions ............................................... 5
1.2 Structure of this document ................................ 5
1.3 Contributors .............................................. 5
2 Motivation ................................................ 6
3 Packet Format ............................................. 7
3.1 Return Codes .............................................. 10
3.2 Target FEC Stack .......................................... 12
3.2.1 LDP IPv4 Prefix ........................................... 13
3.2.2 LDP IPv6 Prefix ........................................... 13
3.2.3 RSVP IPv4 Session ......................................... 14
3.2.4 RSVP IPv6 Session ......................................... 14
3.2.5 VPN IPv4 Prefix ........................................... 15
3.2.6 VPN IPv6 Prefix ........................................... 15
3.2.7 L2 VPN Endpoint ........................................... 15
3.2.8 FEC 128 Pseudowire (Deprecated) ........................... 16
3.2.9 FEC 128 Pseudowire (Current) .............................. 16
3.2.10 FEC 129 Pseudowire ........................................ 17
3.2.11 BGP Labeled IPv4 Prefix ................................... 17
3.2.12 Generic IPv4 Prefix ....................................... 18
3.2.13 Generic IPv6 Prefix ....................................... 18
3.2.14 Nil FEC ................................................... 19
3.3 Downstream Mapping ........................................ 20
3.3.1 Multipath Information Encoding ............................ 23
3.3.2 Downstream Router and Interface ........................... 24
3.4 Pad TLV ................................................... 25
3.5 Error Code ................................................ 25
3.6 Vendor Enterprise Code .................................... 25
3.7 Interface and Label Stack Object .......................... 26
3.7.1 IPv4 Interface and Label Stack Object ..................... 26
3.7.2 IPv6 Interface and Label Stack Object ..................... 27
3.8 Errored TLVs .............................................. 28
3.9 Reply TOS Byte TLV ........................................ 29
4 Theory of Operation ....................................... 29
4.1 Dealing with Equal-Cost Multi-Path (ECMP) ................. 29
4.2 Testing LSPs That Are Used to Carry MPLS Payloads ......... 30
4.3 Sending an MPLS Echo Request .............................. 31
4.4 Receiving an MPLS Echo Request ............................ 31
4.5 Sending an MPLS Echo Reply ................................ 35
4.6 Receiving an MPLS Echo Reply .............................. 36
4.7 Issue with VPN IPv4 and IPv6 Prefixes ..................... 36
4.8 Non-compliant Routers ..................................... 37
5 References ................................................ 37
6 Security Considerations ................................... 38
7 IANA Considerations ....................................... 38
7.1 Message Types, Reply Modes, Return Codes .................. 39
7.2 TLVs ...................................................... 39
8 Acknowledgments ........................................... 39
A Appendix .................................................. 40
A.1 CR-LDP FEC ................................................ 40
A.2 Downstream Mapping for CR-LDP ............................. 40
1. Introduction 1. Introduction
This document describes a simple and efficient mechanism that can be This document describes a simple and efficient mechanism that can be
used to detect data plane failures in MPLS LSPs. There are two parts used to detect data plane failures in MPLS LSPs. There are two parts
to this document: information carried in an MPLS "echo request" and to this document: information carried in an MPLS "echo request" and
"echo reply"; and mechanisms for transporting the echo reply. The "echo reply"; and mechanisms for transporting the echo reply. The
first part aims at providing enough information to check correct first part aims at providing enough information to check correct
operation of the data plane, as well as a mechanism to verify the operation of the data plane, as well as a mechanism to verify the
data plane against the control plane, and thereby localize faults. data plane against the control plane, and thereby localize faults.
The second part suggests two methods of reliable reply channels for The second part suggests two methods of reliable reply channels for
the echo request message, for more robust fault isolation. the echo request message, for more robust fault isolation.
An important consideration in this design is that MPLS echo requests An important consideration in this design is that MPLS echo requests
follow the same data path that normal MPLS packets would traverse. follow the same data path that normal MPLS packets would traverse.
MPLS echo requests are meant primarily to validate the data plane, MPLS echo requests are meant primarily to validate the data plane,
and secondarily to verify the data plane against the control plane. and secondarily to verify the data plane against the control plane.
Mechanisms to check the control plane are valuable, but are not cov-
Mechanisms to check the control plane are valuable, but are not ered in this document.
covered in this document.
To avoid potential Denial of Service attacks, it is recommended to To avoid potential Denial of Service attacks, it is recommended to
regulate the LSP ping traffic going to the control plane. A rate regulate the LSP ping traffic going to the control plane. A rate
limiter should be applied to the well-known UDP port defined below. limiter should be applied to the well-known UDP port defined below.
1.1. Conventions 1.1. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [KEYWORDS]. document are to be interpreted as described in RFC 2119 [KEYWORDS].
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1.2. Structure of this document 1.2. Structure of this document
The body of this memo contains four main parts: motivation, MPLS echo The body of this memo contains four main parts: motivation, MPLS echo
request/reply packet format, LSP ping operation, and a reliable request/reply packet format, LSP ping operation, and a reliable
return path. It is suggested that first-time readers skip the actual return path. It is suggested that first-time readers skip the actual
packet formats and read the Theory of Operation first; the document packet formats and read the Theory of Operation first; the document
is structured the way it is to avoid forward references. is structured the way it is to avoid forward references.
1.3. Contributors 1.3. Contributors
The following made vital contributions to all aspects of this The following made vital contributions to all aspects of this docu-
document, and much of the material came out of debate and discussion ment, and much of the material came out of debate and discussion
among this group. among this group.
Ronald P. Bonica, Juniper Networks, Inc. Ronald P. Bonica, Juniper Networks, Inc.
Dave Cooper, Global Crossing Dave Cooper, Global Crossing
Ping Pan, Hammerhead Systems Ping Pan, Hammerhead Systems
Nischal Sheth, Juniper Networks, Inc. Nischal Sheth, Juniper Networks, Inc.
Sanjay Wadhwa, Juniper Networks, Inc. Sanjay Wadhwa, Juniper Networks, Inc.
2. Motivation 2. Motivation
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test be carried out by sending a packet (called an "MPLS echo test be carried out by sending a packet (called an "MPLS echo
request") along the same data path as other packets belonging to this request") along the same data path as other packets belonging to this
FEC. An MPLS echo request also carries information about the FEC FEC. An MPLS echo request also carries information about the FEC
whose MPLS path is being verified. This echo request is forwarded whose MPLS path is being verified. This echo request is forwarded
just like any other packet belonging to that FEC. In "ping" mode just like any other packet belonging to that FEC. In "ping" mode
(basic connectivity check), the packet should reach the end of the (basic connectivity check), the packet should reach the end of the
path, at which point it is sent to the control plane of the egress path, at which point it is sent to the control plane of the egress
LSR, which then verifies whether it is indeed an egress for the FEC. LSR, which then verifies whether it is indeed an egress for the FEC.
In "traceroute" mode (fault isolation), the packet is sent to the In "traceroute" mode (fault isolation), the packet is sent to the
control plane of each transit LSR, which performs various checks that control plane of each transit LSR, which performs various checks that
it is indeed a transit LSR for this path; this LSR also returns it is indeed a transit LSR for this path; this LSR also returns fur-
further information that helps check the control plane against the ther information that helps check the control plane against the data
data plane, i.e., that forwarding matches what the routing protocols plane, i.e., that forwarding matches what the routing protocols
determined as the path. determined as the path.
One way these tools can be used is to periodically ping a FEC to One way these tools can be used is to periodically ping a FEC to
ensure connectivity. If the ping fails, one can then initiate a ensure connectivity. If the ping fails, one can then initiate a
traceroute to determine where the fault lies. One can also traceroute to determine where the fault lies. One can also periodi-
periodically traceroute FECs to verify that forwarding matches the cally traceroute FECs to verify that forwarding matches the control
control plane; however, this places a greater burden on transit LSRs plane; however, this places a greater burden on transit LSRs and thus
and thus should be used with caution. should be used with caution.
3. Packet Format 3. Packet Format
An MPLS echo request is a (possibly labelled) IPv4 or IPv6 UDP An MPLS echo request is a (possibly labelled) IPv4 or IPv6 UDP
packet; the contents of the UDP packet have the following format: packet; the contents of the UDP packet have the following format:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version Number | Must Be Zero | | Version Number | Global Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Reply mode | Return Code | Return Subcode| | Message Type | Reply mode | Return Code | Return Subcode|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender's Handle | | Sender's Handle |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number | | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TimeStamp Sent (seconds) | | TimeStamp Sent (seconds) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TimeStamp Sent (microseconds) | | TimeStamp Sent (microseconds) |
skipping to change at page 5, line 22 skipping to change at page 7, line 45
The Version Number is currently 1. (Note: the Version Number is to The Version Number is currently 1. (Note: the Version Number is to
be incremented whenever a change is made that affects the ability of be incremented whenever a change is made that affects the ability of
an implementation to correctly parse or process an MPLS echo an implementation to correctly parse or process an MPLS echo
request/reply. These changes include any syntactic or semantic request/reply. These changes include any syntactic or semantic
changes made to any of the fixed fields, or to any TLV or sub-TLV changes made to any of the fixed fields, or to any TLV or sub-TLV
assignment or format that is defined at a certain version number. assignment or format that is defined at a certain version number.
The Version Number may not need to be changed if an optional TLV or The Version Number may not need to be changed if an optional TLV or
sub-TLV is added.) sub-TLV is added.)
The Global Flags field is a bit vector with the following format:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SBZ |V|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
One flag is defined for now, the V bit; the rest SHOULD be set to
zero when sending, and ignored on receipt.
The V (Validate FEC Stack) flag is set to 1 if the sender wants the
receiver to perform FEC stack validation; if V is 0, the choice is
left to the receiver.
The Message Type is one of the following: The Message Type is one of the following:
Value Meaning Value Meaning
----- ------- ----- -------
1 MPLS Echo Request 1 MPLS Echo Request
2 MPLS Echo Reply 2 MPLS Echo Reply
The Reply Mode can take one of the following values: The Reply Mode can take one of the following values:
Value Meaning Value Meaning
----- ------- ----- -------
1 Do not reply 1 Do not reply
2 Reply via an IPv4/IPv6 UDP packet 2 Reply via an IPv4/IPv6 UDP packet
3 Reply via an IPv4/IPv6 UDP packet with Router Alert 3 Reply via an IPv4/IPv6 UDP packet with Router Alert
4 Reply via application level control channel 4 Reply via application level control channel
An MPLS echo request with "Do not reply" may be used for one-way An MPLS echo request with "Do not reply" may be used for one-way con-
connectivity tests; the receiving router may log gaps in the sequence nectivity tests; the receiving router may log gaps in the sequence
numbers and/or maintain delay/jitter statistics. An MPLS echo numbers and/or maintain delay/jitter statistics. An MPLS echo
request would normally have "Reply via an IPv4/IPv6 UDP packet"; if request would normally have "Reply via an IPv4/IPv6 UDP packet"; if
the normal IP return path is deemed unreliable, one may use "Reply the normal IP return path is deemed unreliable, one may use "Reply
via an IPv4/IPv6 UDP packet with Router Alert" (note that this via an IPv4/IPv6 UDP packet with Router Alert" (note that this
requires that all intermediate routers understand and know how to requires that all intermediate routers understand and know how to
forward MPLS echo replies). The echo reply uses the same IP version forward MPLS echo replies). The echo reply uses the same IP version
number as the received echo request, i.e., an IPv4 encapsulated echo number as the received echo request, i.e., an IPv4 encapsulated echo
reply is sent in response to an IPv4 encapsulated echo request. reply is sent in response to an IPv4 encapsulated echo request.
Any application which supports an IP control channel between its Any application which supports an IP control channel between its con-
control entities may set the Reply Mode to 4 to ensure that replies trol entities may set the Reply Mode to 4 to ensure that replies use
use that same channel. Further definition of this codepoint is that same channel. Further definition of this codepoint is applica-
application specific and thus beyond the scope of this docuemnt. tion specific and thus beyond the scope of this docuemnt.
Return Codes and Subcodes are described in the next section. Return Codes and Subcodes are described in the next section.
The Sender's Handle is filled in by the sender, and returned the Sender's Handle is filled in by the sender, and returned
unchanged by the receiver in the echo reply (if any). There are no unchanged by the receiver in the echo reply (if any). There are no
semantics associated with this handle, although a sender may find semantics associated with this handle, although a sender may find
this useful for matching up requests with replies. this useful for matching up requests with replies.
The Sequence Number is assigned by the sender of the MPLS echo The Sequence Number is assigned by the sender of the MPLS echo
request, and can be (for example) used to detect missed replies. request, and can be (for example) used to detect missed replies.
The TimeStamp Sent is the time-of-day (in seconds and microseconds, The TimeStamp Sent is the time-of-day (in seconds and microseconds,
wrt the sender's clock) when the MPLS echo request is sent. The wrt the sender's clock) when the MPLS echo request is sent. The
TimeStamp Received in an echo reply is the time-of-day (wrt the TimeStamp Received in an echo reply is the time-of-day (wrt the
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value | | Value |
. . . .
. . . .
. . . .
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Types are defined below; Length is the length of the Value field in Types are defined below; Length is the length of the Value field in
octets. The Value field depends on the Type; it is zero padded to octets. The Value field depends on the Type; it is zero padded to
align to a four-octet boundary. align to a four-octet boundary. TLVs may be nested within other
TLVs, in which case the nested TLVs are called sub-TLVs.
Two examples follow. The LDP IPv4 FEC TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 1 (LDP IPv4 FEC) | Length = 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Length for this TLV is 5. A FEC TLV which contains just an LDP
IPv4 FEC sub-TLV has the format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 1 (FEC TLV) | Length = 12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-Type = 1 (LDP IPv4 FEC) | Length = 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A description of the Types and Values of the top level TLVs for LSP
ping are given below:
Type # Value Field Type # Value Field
------ ----------- ------ -----------
1 Target FEC Stack 1 Target FEC Stack
2 Downstream Mapping 2 Downstream Mapping
3 Pad 3 Pad
4 Error Code 4 Error Code
5 Vendor Enterprise Code 5 Vendor Enterprise Code
6 TBD 6 TBD
7 IPv4 Interface and Label Stack Object 7 IPv4 Interface and Label Stack Object
8 IPv6 Interface and Label Stack Object 8 IPv6 Interface and Label Stack Object
9 Errored TLVs 9 Errored TLVs
10 Reply TOS Byte
Types with the high order bit not set (i.e., 1) are mandatory TLVs Types less than 32768 (i.e., with the high order bit equal to 0) are
that MUST either be supported by an implementation or result in the mandatory TLVs that MUST either be supported by an implementation or
return code of 2 ("One or more of the TLVs was not understood") being result in the return code of 2 ("One or more of the TLVs was not
sent in the echo response. understood") being sent in the echo response.
Types with the high order bit not set (i.e., 0) are optional TLVs Types greater than or equal to 32768 (i.e., with the high order bit
that MUST be ignored if the implementation does not support or equal to 1) are optional TLVs that SHOULD be ignored if the implemen-
understand them. tation does not understand or support them.
3.1. Return Codes 3.1. Return Codes
The Return Code is set to zero by the sender. The receiver can set The Return Code is set to zero by the sender. The receiver can set
it to one of the values listed below. The notation <RSC> refers to it to one of the values listed below. The notation <RSC> refers to
the Return Subcode. This field is filled in with the stack-depth for the Return Subcode. This field is filled in with the stack-depth for
those codes which specify that. For all other codes the Return those codes which specify that. For all other codes the Return Sub-
Subcode MUST be set to zero. code MUST be set to zero.
Value Meaning Value Meaning
----- ------- ----- -------
0 No return code or return code contained in the Error 0 No return code or return code contained in the Error
Code TLV Code TLV
1 Malformed echo request received 1 Malformed echo request received
2 One or more of the TLVs was not understood 2 One or more of the TLVs was not understood
skipping to change at page 8, line 4 skipping to change at page 11, line 36
8 Label switched at stack-depth <RSC> 8 Label switched at stack-depth <RSC>
9 Label switched but no MPLS forwarding at stack-depth 9 Label switched but no MPLS forwarding at stack-depth
<RSC> <RSC>
10 Mapping for this FEC is not the given label at stack 10 Mapping for this FEC is not the given label at stack
depth <RSC> depth <RSC>
11 No label entry at stack-depth <RSC> 11 No label entry at stack-depth <RSC>
12 Protocol not associated with interface at FEC stack 12 Protocol not associated with interface at FEC stack
depth <RSC> depth <RSC>
13 Premature termination of ping due to label stack 13 Premature termination of ping due to label stack
shrinking to a single label shrinking to a single label
Note 1. The Return Subcode contains the point in the label stack Note 1
where processing was terminated. If the RSC is 0, no labels
were processed. Otherwise the packet would have been label The Return Subcode contains the point in the label stack" where pro-
switched at depth RSC. cessing was terminated. If the RSC is 0, no labels were processed.
Otherwise the packet would have been label switched at depth RSC.
3.2. Target FEC Stack 3.2. Target FEC Stack
A Target FEC Stack is a list of sub-TLVs. The number of elements is A Target FEC Stack is a list of sub-TLVs. The number of elements is
determined by the looking at the sub-TLV length fields. determined by the looking at the sub-TLV length fields.
Sub-Type # Length Value Field Sub-Type # Length Value Field
---------- ------ ----------- ---------- ------ -----------
1 5 LDP IPv4 prefix 1 5 LDP IPv4 prefix
2 17 LDP IPv6 prefix 2 17 LDP IPv6 prefix
3 20 RSVP IPv4 Session Query 3 20 RSVP IPv4 Session Query
4 56 RSVP IPv6 Session Query 4 56 RSVP IPv6 Session Query
5 Reserved; see Appendix 5 Reserved; see Appendix
6 13 VPN IPv4 prefix 6 13 VPN IPv4 prefix
7 25 VPN IPv6 prefix 7 25 VPN IPv6 prefix
8 14 L2 VPN endpoint 8 14 L2 VPN endpoint
9 10 "FEC 128" Pseudowire (old) 9 10 "FEC 128" Pseudowire (old)
10 14 "FEC 128" Pseudowire (new) 10 14 "FEC 128" Pseudowire (new)
11 13+ "FEC 129" Pseudowire 11 13+ "FEC 129" Pseudowire
12 10 BGP labeled IPv4 prefix 12 9 BGP labeled IPv4 prefix
13 ?? BGP labeled IPv6 prefix (TBD)
14 5 Generic IPv4 prefix
15 17 Generic IPv6 prefix
16 4*N Nil FEC
Other FEC Types will be defined as needed. Other FEC Types will be defined as needed.
Note that this TLV defines a stack of FECs, the first FEC element Note that this TLV defines a stack of FECs, the first FEC element
corresponding to the top of the label stack, etc. corresponding to the top of the label stack, etc.
An MPLS echo request MUST have a Target FEC Stack that describes the An MPLS echo request MUST have a Target FEC Stack that describes the
FEC stack being tested. For example, if an LSR X has an LDP mapping FEC stack being tested. For example, if an LSR X has an LDP mapping
for 192.168.1.1 (say label 1001), then to verify that label 1001 does for 192.168.1.1 (say label 1001), then to verify that label 1001 does
indeed reach an egress LSR that announced this prefix via LDP, X can indeed reach an egress LSR that announced this prefix via LDP, X can
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0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote PE Address | | Remote PE Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VC ID | | VC ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encapsulation Type | Must Be Zero | | Encapsulation Type | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This FEC will be deprecated, and is retained only for backward This FEC will be deprecated, and is retained only for backward com-
compatibility. Implementations of LSP ping SHOULD accept and process patibility. Implementations of LSP ping SHOULD accept and process
this TLV, but SHOULD send LSP ping echo requests with the new TLV this TLV, but SHOULD send LSP ping echo requests with the new TLV
(see next section), unless explicitly asked by configuration to use (see next section), unless explicitly asked by configuration to use
the old TLV. the old TLV.
An LSR receiving this TLV SHOULD use the source IP address of the LSP An LSR receiving this TLV SHOULD use the source IP address of the LSP
echo request to infer the Sender's PE Address. echo request to infer the Sender's PE Address.
3.2.9. FEC 128 Pseudowire (Current) 3.2.9. FEC 128 Pseudowire (Current)
The value field consists of the sender's PE address (the source The value field consists of the sender's PE address (the source
skipping to change at page 13, line 17 skipping to change at page 17, line 28
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender's PE Address | | Sender's PE Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote PE Address | | Remote PE Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PW Type | AGI Length | SAII Length | | PW Type | AGI Length | SAII Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TAII Length | AGI Value ... SAII Value ... TAII Value ... | TAII Length | AGI Value ... SAII Value ... TAII Value ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ... . . ... .
. . . .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... | 0-3 octets of zero padding | | ... | 0-3 octets of zero padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Length of this TLV is 13 + AGI length + SAII length + TAII The Length of this TLV is 13 + AGI length + SAII length + TAII
length. Padding is used to make the total length a multiple of 4; length. Padding is used to make the total length a multiple of 4;
the length of the padding is not included in the Length field. the length of the padding is not included in the Length field.
3.2.11. BGP Labeled IPv4 Prefix 3.2.11. BGP Labeled IPv4 Prefix
The value field consists of the BGP Next Hop associated with the NLRI The value field consists of the BGP Next Hop associated with the NLRI
advertising the prefix and label, the IPv4 prefix (with trailing 0 advertising the prefix and label, the IPv4 prefix (with trailing 0
skipping to change at page 13, line 46 skipping to change at page 18, line 15
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BGP Next Hop | | BGP Next Hop |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Prefix | | IPv4 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | Must Be Zero | | Prefix Length | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.12. Generic IPv4 Prefix
The value consists of four octets of an IPv4 prefix followed by one
octet of prefix length in bits; the format is given below. The IPv4
prefix is in network byte order; if the prefix is shorter than 32
bits, trailing bits SHOULD be set to zero. This FEC is used if the
protocol advertising the label is unknown, or may change during the
course of the LSP. An example is an inter-AS LSP that may be sig-
naled by LDP in one AS, by RSVP-TE in another AS, and by BGP between
the ASes, such as is common for inter-AS VPNs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.13. Generic IPv6 Prefix
The value consists of sixteen octets of an IPv6 prefix followed by
one octet of prefix length in bits; the format is given below. The
IPv6 prefix is in network byte order; if the prefix is shorter than
128 bits, the trailing bits SHOULD be set to zero.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 prefix |
| (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.14. Nil FEC
At times labels from the reserved range, e.g. Router Alert and
Explicit-null, may be added to the label stack for various diagnostic
purposes such as influencing load-balancing. These labels may have
no explicit FEC associated with them. The Nil FEC stack is defined
to allow a Target FEC stack subtlv to be added to the target FEC
stack to account for such labels so that proper validation can still
be performed.
The Length is 4*N octets, where N is the number of Labels contained
in the Nil FEC stack.
Labels are 20 bit values treated as numbers. The first label speci-
fied correspond with the label nearest the top of the label stack.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label 1 | SBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label 2 | SBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Label 1, Label 2, ... are the actual labels inserted in the label
stack; the SBZ fields SHOULD be zero when sent, and ignored on
receipt.
3.3. Downstream Mapping 3.3. Downstream Mapping
The Downstream Mapping object is an optional TLV. Only one The Downstream Mapping object is an optional TLV. Only one Down-
Downstream Mapping request may appear in and echo request. The stream Mapping request may appear in and echo request. The presence
presence of a Downstream Mapping object is a request that Downstream of a Downstream Mapping object is a request that Downstream Mapping
Mapping objects be included in the echo reply. If the replying objects be included in the echo reply. If the replying router is the
router is the destination of the FEC, then a Downstream Mapping TLV destination of the FEC, then a Downstream Mapping TLV SHOULD NOT be
SHOULD NOT be included in the echo reply. Otherwise Downstream included in the echo reply. Otherwise Downstream Mapping objects
Mapping objects SHOULD include a Downstream Mapping object for each SHOULD include a Downstream Mapping object for each interface over
interface over which this FEC could be forwarded. For a more precise which this FEC could be forwarded. For a more precise definition of
definition of the notion of "downstream", see the section named the notion of "downstream", see the section named "Downstream".
"Downstream".
The Length is 16 + M + 4*N octets, where M is the Multipath Length, The Length is 16 + M + 4*N octets, where M is the Multipath Length,
and N is the number of Downstream Labels. The Value field of a and N is the number of Downstream Labels. The Value field of a Down-
Downstream Mapping has the following format: stream Mapping has the following format:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTU | Address Type | Resvd (SBZ) | | MTU | Address Type | DS Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream IP Address (4 or 16 octets) | | Downstream IP Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream Interface Address (4 or 16 octets) | | Downstream Interface Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hash Key Type | Depth Limit | Multipath Length | | Multipath Type| Depth Limit | Multipath Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . .
. (Multipath Information) . . (Multipath Information) .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream Label | Protocol | | Downstream Label | Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . .
. . . .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream Label | Protocol | | Downstream Label | Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Maximum Transmission Unit (MTU) Maximum Transmission Unit (MTU)
The MTU is the largest MPLS frame (including label stack) that The MTU is the largest MPLS frame (including label stack) that fits
fits on the interface to the Downstream LSR. on the interface to the Downstream LSR.
Address Type Address Type
The Address Type indicates if the interface is numbered or The Address Type indicates if the interface is numbered or unnumbered
unnumbered and is set to one of the following values: and is set to one of the following values:
Type # Address Type Type # Address Type
------ ------------ ------ ------------
1 IPv4 1 IPv4 Numbered
2 Unnumbered 2 IPv4 Unnumbered
3 IPv6 3 IPv6 Numbered
4 IPv6 Unnumbered
Reserved DS Flags
The field marked SBZ SHOULD be set to zero when sending and The DS Flags field is a bit vector with the following format:
SHOULD be ignored on receipt.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Rsvd(MBZ) |I|N|
+-+-+-+-+-+-+-+-+
Two flags are defined currently, I and N. The remaining flags MUST
be set to zero when sending, and ignored on receipt.
Flag Name and Meaning
---- ----------------
I Interface and Label Stack Object Request
When this flag is set, it indicates that the replying
router should include an Interface and Label Stack
Object in the Echo-Reply message
N Treat as a Non-IP Packet
Echo-Request messages will be used to diagnose non-IP
flows. However, these messages are carried in IP
packets. For a router which alters its ECMP algorithm
based on the FEC or deep packet examinition, this flag
requests that the router treat this as it would if the
determination of an IP payload had failed.
Downstream IP Address and Downstream Interface Address Downstream IP Address and Downstream Interface Address
If the interface to the downstream LSR is numbered, then the If the interface to the downstream LSR is numbered, then the Address
Address Type MUST be set to IPv4 or IPv6, the Downstream IP Type MUST be set to IPv4 or IPv6, the Downstream IP Address MUST be
Address MUST be set to either the downstream LSR's Router ID or set to either the downstream LSR's Router ID or the interface address
the interface address of the downstream LSR, and the Downstream of the downstream LSR, and the Downstream Interface Address MUST be
Interface Address MUST be set to the downstream LSR's interface set to the downstream LSR's interface address.
address.
If the interface to the downstream LSR is unnumbered, the Address If the interface to the downstream LSR is unnumbered, the Address
Type MUST be Unnumbered, the Downstream IP Address MUST be the Type MUST be Unnumbered, the Downstream IP Address MUST be the down-
downstream LSR's Router ID (4 octets), and the Downstream stream LSR's Router ID (4 octets), and the Downstream Interface
Interface Address MUST be set to the index assigned by the Address MUST be set to the index assigned by the upstream LSR to the
upstream LSR to the interface. interface.
Multipath Type
The follow Mutipath Types are defined:
Key Type Multipath Information
--- ---------------- ---------------------
0 no multipath (empty; M = 0)
2 IP address IP addresses
4 IP address range low/high address pairs
8 Bit-masked IPv4 IP address prefix and bit mask
address set
9 Bit-masked label set Label prefix and bit mask
Type 0 indicates that all packets will be forwarded out this one
interface.
Types 2, 4, 8 and 9 specify that the supplied Multipath Information
will serve to execise this path.
Depth Limit
The Depth Limit is applicable only to a label stack, and is the maxi-
mum number of labels considered in the hash; this SHOULD be set to
zero if unspecified or unlimited.
Multipath Length Multipath Length
The length in octets of the Multipath Information. The length in octets of the Multipath Information.
Multipath Information
Address or label values encoded according to the Multipath Type. See
the next section below for encoding details.
Downstream Label(s) Downstream Label(s)
The set of labels in the label stack as it would have appeared if The set of labels in the label stack as it would have appeared if
this router were forwarding the packet through this interface. this router were forwarding the packet through this interface. Any
Any Implicit Null labels are explicitly inluded. Labels are Implicit Null labels are explicitly inluded. Labels are treated as
treated as numbers, i.e. they are right justified in the field. numbers, i.e. they are right justified in the field.
A Downstream Label is 24 bits, in the same format as an MPLS A Downstream Label is 24 bits, in the same format as an MPLS label
label minus the TTL field, i.e., the MSBit of the label is bit 0, minus the TTL field, i.e., the MSBit of the label is bit 0, the LSbit
the LSbit is bit 19, the EXP bits are bits 20-22, and bit 23 is is bit 19, the EXP bits are bits 20-22, and bit 23 is the S bit. The
the S bit. The replying router SHOULD fill in the EXP and S replying router SHOULD fill in the EXP and S bits; the LSR receiving
bits; the LSR receiving the echo reply MAY choose to ignore these the echo reply MAY choose to ignore these bits.
bits.
Protocol Protocol
The Protocol is taken from the following table: The Protocol is taken from the following table:
Protocol # Signaling Protocol Protocol # Signaling Protocol
---------- ------------------ ---------- ------------------
0 Unknown 0 Unknown
1 Static 1 Static
2 BGP 2 BGP
3 LDP 3 LDP
4 RSVP-TE 4 RSVP-TE
5 Reserved; see Appendix 5 Reserved; see Appendix
Depth Limit 3.3.1. Multipath Information Encoding
The Depth Limit is applicable only to a label stack, and is the
maximum number of labels considered in the hash; this SHOULD be
set to zero if unspecified or unlimited.
Multipath Information
The multipath information encodes labels or addresses which will The multipath information encodes labels or addresses which will
exercise this path. The multipath informaiton depends on the exercise this path. The multipath informaiton depends on the multi-
hash key type. The contents of the field are shown in the table path type. The contents of the field are shown in the table above.
above. IP addresses are drawn from the range 127/8. Labels are IP addresses are drawn from the range 127/8. Labels are treated as
treated as numbers, i.e. they are right justified in the field. numbers, i.e. they are right justified in the field. Label and
Label and Address pairs MUST NOT overlap and MUST be in ascending Address pairs MUST NOT overlap and MUST be in ascending sequence.
sequence.
Hash key 8 allows a denser encoding of IP address. The IPv4 Type 8 allows a denser encoding of IP address. The IPv4 prefix is
prefix is formatted as a base IPv4 address with the non-prefix formatted as a base IPv4 address with the non-prefix low order bits
low order bits set to zero. The maximum prefix length is 27. set to zero. The maximum prefix length is 27. Following the prefix
Following the prefix is a mask of length 2^(32-prefix length) is a mask of length 2^(32-prefix length) bits. Each bit set to one
bits. Each bit set to one represents a valid address. The represents a valid address. The address is the base IPv4 address
address is the base IPv4 address plus the position of the bit in plus the position of the bit in the mask where the bits are numbered
left to right begining with zero.
Type 9 allows a denser encoding of Labels. The label prefix is for-
matted as a base label value with the non-prefix low order bits set
to zero. The maximum prefix (including leading zeros due to encod-
ing) length is 27. Following the prefix is a mask of length
2^(32-prefix length) bits. Each bit set to one represents a valid
Label. The label is the base label plus the position of the bit in
the mask where the bits are numbered left to right begining with the mask where the bits are numbered left to right begining with
zero. zero.
Hash key 9 allows a denser encoding of Labels. The label prefix If the received multipath information is non-null, the labels and IP
is formatted as a base label value with the non-prefix low order addresses MUST be picked from the set provided. If none of these
bits set to zero. The maximum prefix (including leading zeros labels or addresses map to a particular downstream interface, then
due to encoding) length is 27. Following the prefix is a mask of for that interface, the type MUST be set to 0. If the received mul-
length 2^(32-prefix length) bits. Each bit set to one represents tipath information is null, the receiver simply returns null.
a valid Label. The label is the base label plus the position of
the bit in the mask where the bits are numbered left to right
begining with zero.
If the received multipath information is non-null, the labels and
IP addresses MUST be picked from the set provided or the Hash Key
Type MUST be set to 7. If the received multipath information is
null, the receiver simply returns null.
For example, suppose LSR X at hop 10 has two downstream LSRs Y For example, suppose LSR X at hop 10 has two downstream LSRs Y and Z
and Z for the FEC in question. X could return Hash Key Type 4, for the FEC in question. The received X could return Hash Key Type
with low/high IP addresses of 1.1.1.1->1.1.1.255 for downstream 4, with low/high IP addresses of 1.1.1.1->1.1.1.255 for downstream
LSR Y and 2.1.1.1->2.1.1.255 for downstream LSR Z. The head end LSR Y and 2.1.1.1->2.1.1.255 for downstream LSR Z. The head end
reflects this information to LSR Y. Y, which has three reflects this information to LSR Y. Y, which has three downstream
downstream LSRs U, V and W, computes that 1.1.1.1->1.1.1.127 LSRs U, V and W, computes that 1.1.1.1->1.1.1.127 would go to U and
would go to U and 1.1.1.128-> 1.1.1.255 would go to V. Y would 1.1.1.128-> 1.1.1.255 would go to V. Y would then respond with 3
then respond with 3 Downstream Mappings: to U, with Hash Key Type Downstream Mappings: to U, with Hash Key Type 4 (1.1.1.1->1.1.1.127);
4 (1.1.1.1->1.1.1.127); to V, with Hash Key Type 4 to V, with Hash Key Type 4 (1.1.1.127->1.1.1.255); and to W, with
(1.1.1.127->1.1.1.255); and to W, with Hash Key Type 7. Hash Key Type 7.
3.3.1. "Downstream" Note that computing multi-path information may impose a significant
processing burden on the receiver. A receiver MAY thus choose to
process a subset of the received prefixes. The sender, on receiving
a reply to a Downstream Map with partial information, SHOULD assume
that the prefixes missing in the reply were skipped by the receiver,
and MAY re-request information about them in a new echo request.
3.3.2. Downstream Router and Interface
The notion of "downstream router" and "downstream interface" should The notion of "downstream router" and "downstream interface" should
be explained. Consider an LSR X. If a packet that was originated be explained. Consider an LSR X. If a packet that was originated
with TTL n>1 arrived with outermost label L at LSR X, X must be able with TTL n>1 arrived with outermost label L at LSR X, X must be able
to compute which LSRs could receive the packet if it was originated to compute which LSRs could receive the packet if it was originated
with TTL=n+1, over which interface the request would arrive and what with TTL=n+1, over which interface the request would arrive and what
label stack those LSRs would see. (It is outside the scope of this label stack those LSRs would see. (It is outside the scope of this
document to specify how this computation is done.) The set of these document to specify how this computation is done.) The set of these
LSRs/interfaces are the downstream routers/interfaces (and their LSRs/interfaces are the downstream routers/interfaces (and their
corresponding labels) for X with respect to L. Each pair of corresponding labels) for X with respect to L. Each pair of down-
downstream router and interface requires a separate Downstream stream router and interface requires a separate Downstream Mapping to
Mapping to be added to the reply. (Note that there are multiple be added to the reply. (Note that there are multiple Downstream
Downstream Label fields in each TLV as the incoming label L may be Label fields in each TLV as the incoming label L may be swapped with
swapped with a label stack.) a label stack.)
The case where X is the LSR originating the echo request is a special The case where X is the LSR originating the echo request is a special
case. X needs to figure out what LSRs would receive the MPLS echo case. X needs to figure out what LSRs would receive the MPLS echo
request for a given FEC Stack that X originates with TTL=1. request for a given FEC Stack that X originates with TTL=1.
The set of downstream routers at X may be alternative paths (see the The set of downstream routers at X may be alternative paths (see the
discussion below on ECMP) or simultaneous paths (e.g., for MPLS discussion below on ECMP) or simultaneous paths (e.g., for MPLS mul-
multicast). In the former case, the Multipath sub-field is used as a ticast). In the former case, the Multipath sub-field is used as a
hint to the sender as to how it may influence the choice of these hint to the sender as to how it may influence the choice of these
alternatives. The "No of Multipaths" is the number of IP alternatives. The "No of Multipaths" is the number of IP
Address/Next Label fields. The Hash Key Type is taken from the Address/Next Label fields.
following table:
Key Type Multipath Information
--- ---------------- ---------------------
0 no multipath (empty; M = 0)
1 label labels
2 IP address IP addresses
3 label range low/high label pairs
4 IP address range low/high address pairs
5 no more labels (empty; M = 0)
6 All IP addresses (empty; M = 0)
7 no match (empty; M = 0)
8 Bit-masked IPv4 IP address prefix and bit mask
address set
9 Bit-masked label set Label prefix and bit mask
Type 0 indicates that all packets will be forwarded out this one
interface.
Types 1, 2, 3, 4, 8 and 9 specify that the supplied Multipath
Information will serve to execise this path.
Types 5 and 6 are TBD.
Type 7 indicates that no matches are possible given the Multipath
Information in the received DS mapping information.
3.4. Pad TLV 3.4. Pad TLV
The value part of the Pad TLV contains a variable number (>= 1) of The value part of the Pad TLV contains a variable number (>= 1) of
octets. The first octet takes values from the following table; all octets. The first octet takes values from the following table; all
the other octets (if any) are ignored. The receiver SHOULD verify the other octets (if any) are ignored. The receiver SHOULD verify
that the TLV is received in its entirety, but otherwise ignores the that the TLV is received in its entirety, but otherwise ignores the
contents of this TLV, apart from the first octet. contents of this TLV, apart from the first octet.
Value Meaning Value Meaning
----- ------- ----- -------
1 Drop Pad TLV from reply 1 Drop Pad TLV from reply
2 Copy Pad TLV to reply 2 Copy Pad TLV to reply
3-255 Reserved for future use 3-255 Reserved for future use
3.5. Error Code 3.5. Error Code
The Error Code TLV is currently not defined; its purpose is to The Error Code TLV is currently not defined; its purpose is to pro-
provide a mechanism for a more elaborate error reporting structure, vide a mechanism for a more elaborate error reporting structure,
should the reason arise. should the reason arise.
3.6. Vendor Enterprise Code 3.6. Vendor Enterprise Code
The Length is always 4; the value is the SMI Enterprise code, in The Length is always 4; the value is the SMI Enterprise code, in net-
network octet order, of the vendor with a Vendor Private extension to work octet order, of the vendor with a Vendor Private extension to
any of the fields in the fixed part of the message, in which case any of the fields in the fixed part of the message, in which case
this TLV MUST be present. If none of the fields in the fixed part of this TLV MUST be present. If none of the fields in the fixed part of
the message have vendor private extensions, this TLV is OPTIONAL. the message have vendor private extensions, this TLV is OPTIONAL.
3.7. Interface and Label Stack Object 3.7. Interface and Label Stack Object
The Interface and Label Stack Object is an optional TLV. It is used The Interface and Label Stack Object is an optional TLV. It is used
in a Reply message to report the interface on which the Request in a Reply message to report the interface on which the Request Mes-
Message was received and the label stack which was on the packet when sage was received and the label stack which was on the packet when it
it was received. Only one such object may appear. The purpose of was received. Only one such object may appear. The purpose of the
the object is to allow the upstream router to obtain the exact object is to allow the upstream router to obtain the exact interface
interface and label stack information as it appears at the replying and label stack information as it appears at the replying LSR. It
LSR. It has two formats, type 7 for IPv4 and type 8 for IPv6 (to be has two formats, type 7 for IPv4 and type 8 for IPv6 (to be assigned
assigned by IANA). by IANA).
3.8. IPv4 Interface and Label Stack Object 3.7.1. IPv4 Interface and Label Stack Object
The Length is 8 + 4*N octets, N is the number of Downstream Labels. The Length is 8 + 4*N octets, N is the number of Downstream Labels.
The value field of a Interface and Label Stack TLV has the following The value field of a Interface and Label Stack TLV has the following
format: format:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream IPv4 Address | | Downstream IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 20, line 4 skipping to change at page 27, line 11
Downstream Interface Address Downstream Interface Address
If the address type is 'IPv4', the interface address field MUST If the address type is 'IPv4', the interface address field MUST
MUST be set to the downstream LSR's interface address. MUST be set to the downstream LSR's interface address.
If the address type is 'unnumbered', interface address field If the address type is 'unnumbered', interface address field
MUST be set to the index assigned by the downstream LSR to the MUST be set to the index assigned by the downstream LSR to the
interface. interface.
Label Stack Label Stack
The label stack of the received echo request message. If any The label stack of the received echo request message. If any
TTL values have been changed by this router, they SHOULD be TTL values have been changed by this router, they SHOULD be
restored. restored.
3.9. IPv6 Interface and Label Stack Object 3.7.2. IPv6 Interface and Label Stack Object
The Length is 32 + 4*N octets, N is the number of Downstream Labels. The Length is 32 + 4*N octets, N is the number of Downstream Labels.
The value field of a Interface and Label Stack TLV has the following The value field of a Interface and Label Stack TLV has the following
format: format:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream IPv6 Address | | Downstream IPv6 Address |
| Downstream IPv6 Address (Cont.) | | Downstream IPv6 Address (Cont.) |
skipping to change at page 21, line 16 skipping to change at page 28, line 24
interface address field MUST be set to the index assigned by interface address field MUST be set to the index assigned by
the downstream LSR to the interface. The remaining 12 octets the downstream LSR to the interface. The remaining 12 octets
MUST be set to zero. MUST be set to zero.
Label Stack Label Stack
The label stack of the received echo request message. If any The label stack of the received echo request message. If any
TTL values have been changed by this router, they SHOULD be TTL values have been changed by this router, they SHOULD be
restored. restored.
3.10. Errored TLVs 3.8. Errored TLVs
The following TLV is an optional TLV defined to be sent back to the The following TLV is an optional TLV defined to be sent back to the
sender of an Echo Request to inform it of Mandatory TLVs either not sender of an Echo Request to inform it of Mandatory TLVs either not
supported by an implementation, or parsed and found to be in error. supported by an implementation, or parsed and found to be in error.
The Value field contains the TLVs not understood encoded as subtlvs. The Value field contains the TLVs not understood encoded as subtlvs.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 32678 | Length | | Type = 9 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value | | Value |
. . . .
. . . .
. . . .
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.9. Reply TOS Byte TLV
This TLV is used by the originator of the echo request to request
that a echo reply be sent with the IP header TOS byte set to
the value specified in the TLV. This TLV has a length of 4 with
the following value field.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reply-TOS Byte| Must be zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4. Theory of Operation 4. Theory of Operation
An MPLS echo request is used to test a particular LSP. The LSP to be An MPLS echo request is used to test a particular LSP. The LSP to be
tested is identified by the "FEC Stack"; for example, if the LSP was tested is identified by the "FEC Stack"; for example, if the LSP was
set up via LDP, and is to an egress IP address of 10.1.1.1, the FEC set up via LDP, and is to an egress IP address of 10.1.1.1, the FEC
stack contains a single element, namely, an LDP IPv4 prefix sub-TLV stack contains a single element, namely, an LDP IPv4 prefix sub-TLV
with value 10.1.1.1/32. If the LSP being tested is an RSVP LSP, the with value 10.1.1.1/32. If the LSP being tested is an RSVP LSP, the
FEC stack consists of a single element that captures the RSVP Session FEC stack consists of a single element that captures the RSVP Session
and Sender Template which uniquely identifies the LSP. and Sender Template which uniquely identifies the LSP.
FEC stacks can be more complex. For example, one may wish to test a FEC stacks can be more complex. For example, one may wish to test a
VPN IPv4 prefix of 10.1/8 that is tunneled over an LDP LSP with VPN IPv4 prefix of 10.1/8 that is tunneled over an LDP LSP with
egress 10.10.1.1. The FEC stack would then contain two sub-TLVs, the egress 10.10.1.1. The FEC stack would then contain two sub-TLVs, the
first being a VPN IPv4 prefix, and the second being an LDP IPv4 first being a VPN IPv4 prefix, and the second being an LDP IPv4 pre-
prefix. If the underlying (LDP) tunnel were not known, or was fix. If the underlying (LDP) tunnel were not known, or was consid-
considered irrelevant, the FEC stack could be a single element with ered irrelevant, the FEC stack could be a single element with just
just the VPN IPv4 sub-TLV. the VPN IPv4 sub-TLV.
When an MPLS echo request is received, the receiver is expected to do When an MPLS echo request is received, the receiver is expected to do
a number of tests that verify that the control plane and data plane a number of tests that verify that the control plane and data plane
are both healthy (for the FEC stack being pinged), and that the two are both healthy (for the FEC stack being pinged), and that the two
planes are in sync. planes are in sync.
4.1. Dealing with Equal-Cost Multi-Path (ECMP) 4.1. Dealing with Equal-Cost Multi-Path (ECMP)
LSPs need not be simple point-to-point tunnels. Frequently, a single LSPs need not be simple point-to-point tunnels. Frequently, a single
LSP may originate at several ingresses, and terminate at several LSP may originate at several ingresses, and terminate at several
egresses; this is very common with LDP LSPs. LSPs for a given FEC egresses; this is very common with LDP LSPs. LSPs for a given FEC
may also have multiple "next hops" at transit LSRs. At an ingress, may also have multiple "next hops" at transit LSRs. At an ingress,
there may also be several different LSPs to choose from to get to the there may also be several different LSPs to choose from to get to the
desired endpoint. Finally, LSPs may have backup paths, detour paths desired endpoint. Finally, LSPs may have backup paths, detour paths
and other alternative paths to take should the primary LSP go down. and other alternative paths to take should the primary LSP go down.
To deal with the last two first: it is assumed that the LSR sourcing To deal with the last two first: it is assumed that the LSR sourcing
MPLS echo requests can force the echo request into any desired LSP, MPLS echo requests can force the echo request into any desired LSP,
so choosing among multiple LSPs at the ingress is not an issue. The so choosing among multiple LSPs at the ingress is not an issue. The
problem of probing the various flavors of backup paths that will problem of probing the various flavors of backup paths that will typ-
typically not be used for forwarding data unless the primary LSP is ically not be used for forwarding data unless the primary LSP is down
down will not be addressed here. will not be addressed here.
Since the actual LSP and path that a given packet may take may not be Since the actual LSP and path that a given packet may take may not be
known a priori, it is useful if MPLS echo requests can exercise all known a priori, it is useful if MPLS echo requests can exercise all
possible paths. This, while desirable, may not be practical, because possible paths. This, while desirable, may not be practical, because
the algorithms that a given LSR uses to distribute packets over the algorithms that a given LSR uses to distribute packets over
alternative paths may be proprietary. alternative paths may be proprietary.
To achieve some degree of coverage of alternate paths, there is a To achieve some degree of coverage of alternate paths, there is a
certain lattitude in choosing the destination IP address and source certain lattitude in choosing the destination IP address and source
UDP port for an MPLS echo request. This is clearly not sufficient; UDP port for an MPLS echo request. This is clearly not sufficient;
in the case of traceroute, more lattitude is offered by means of the in the case of traceroute, more lattitude is offered by means of the
"Multipath Exercise" sub-TLV of the Downstream Mapping TLV. This is "Multipath Exercise" sub-TLV of the Downstream Mapping TLV. This is
used as follows. An ingress LSR periodically sends an MPLS used as follows. An ingress LSR periodically sends an MPLS tracer-
traceroute message to determine whether there are multipaths for a oute message to determine whether there are multipaths for a given
given LSP. If so, each hop will provide some information how each of LSP. If so, each hop will provide some information how each of its
its downstreams can be exercised. The ingress can then send MPLS downstreams can be exercised. The ingress can then send MPLS echo
echo requests that exercise these paths. If several transit LSRs requests that exercise these paths. If several transit LSRs have
have ECMP, the ingress may attempt to compose these to exercise all ECMP, the ingress may attempt to compose these to exercise all possi-
possible paths. However, full coverage may not be possible. ble paths. However, full coverage may not be possible.
4.2. Sending an MPLS Echo Request 4.2. Testing LSPs That Are Used to Carry MPLS Payloads
To detect certain LSP breakages, it may be necessary to encapsulate
an MPLS echo request packet with at least one additional label when
testing LSPs that are used to carry MPLS payloads (such as LSPs used
to carry L2VPN and L3VPN traffic. For example, when testing LDP or
RSVP-TE LSPs, just sending an MPLS echo request packet may not detect
instances where the router immediately upstream of the destination of
the LSP ping may forward the MPLS echo request successfully over an
interface not configured to carry MPLS payloads because of the use of
penultimate hop popping. Since the receiving router has no means to
differentiate whether the IP packet was sent unlabeled or implicitly
labeled, the addition of labels shimmed above the MPLS echo request
(using the Nil FEC) will prevent a router from forwarding such a
packet out unlabeled interfaces.
4.3. Sending an MPLS Echo Request
An MPLS echo request is a (possibly) labelled UDP packet. The IP An MPLS echo request is a (possibly) labelled UDP packet. The IP
header is set as follows: the source IP address is a routable address header is set as follows: the source IP address is a routable address
of the sender; the destination IP address is a (randomly chosen) of the sender; the destination IP address is a (randomly chosen)
address from 127/8; the IP TTL is set to 1. The source UDP port is address from 127/8; the IP TTL is set to 1. The source UDP port is
chosen by the sender; the destination UDP port is set to 3503 chosen by the sender; the destination UDP port is set to 3503
(assigned by IANA for MPLS echo requests). The Router Alert option (assigned by IANA for MPLS echo requests). The Router Alert option
is set in the IP header. is set in the IP header.
If the echo request is labelled, one may (depending on what is being If the echo request is labelled, one may (depending on what is being
pinged) set the TTL of the innermost label to 1, to prevent the ping pinged) set the TTL of the innermost label to 1, to prevent the ping
request going farther than it should. Examples of this include request going farther than it should. Examples of this include ping-
pinging a VPN IPv4 or IPv6 prefix, an L2 VPN end point or a ing a VPN IPv4 or IPv6 prefix, an L2 VPN end point or a pseudowire.
pseudowire. This can also be accomplished by inserting a router This can also be accomplished by inserting a router alert label above
alert label above this label; however, this may lead to the undesired this label; however, this may lead to the undesired side effect that
side effect that MPLS echo requests take a different data path than MPLS echo requests take a different data path than actual data.
actual data.
In "ping" mode (end-to-end connectivity check), the TTL in the In "ping" mode (end-to-end connectivity check), the TTL in the outer-
outermost label is set to 255. In "traceroute" mode (fault isolation most label is set to 255. In "traceroute" mode (fault isolation
mode), the TTL is set successively to 1, 2, .... mode), the TTL is set successively to 1, 2, ....
The sender chooses a Sender's Handle, and a Sequence Number. When The sender chooses a Sender's Handle, and a Sequence Number. When
sending subsequent MPLS echo requests, the sender SHOULD increment sending subsequent MPLS echo requests, the sender SHOULD increment
the sequence number by 1. However, a sender MAY choose to send a the sequence number by 1. However, a sender MAY choose to send a
group of echo requests with the same sequence number to improve the group of echo requests with the same sequence number to improve the
chance of arrival of at least one packet with that sequence number. chance of arrival of at least one packet with that sequence number.
The TimeStamp Sent is set to the time-of-day (in seconds and The TimeStamp Sent is set to the time-of-day (in seconds and
microseconds) that the echo request is sent. The TimeStamp Received microseconds) that the echo request is sent. The TimeStamp Received
is set to zero. is set to zero.
An MPLS echo request MUST have a FEC Stack TLV. Also, the Reply Mode An MPLS echo request MUST have a FEC Stack TLV. Also, the Reply Mode
must be set to the desired reply mode; the Return Code and Subcode must be set to the desired reply mode; the Return Code and Subcode
are set to zero. are set to zero. In the "traceroute" mode, the echo request SHOULD a
Downstream Mapping TLV.
In the "traceroute" mode, the echo request SHOULD contain one or more
Downstream Mapping TLVs. For TTL=1, all the downstream routers (and
corresponding labels) for the sender with respect to the FEC Stack
being pinged SHOULD be sent in the echo request. For n>1, the
Downstream Mapping TLVs from the echo reply for TTL=(n-1) are copied
to the echo request with TTL=n; the sender MAY choose to reduce the
size of a "Downstream Multipath Mapping TLV" when copying into the
next echo request as long as the Hash Key Type matching the label or
IP address used to exercise the current MP is still present.
4.3. Receiving an MPLS Echo Request 4.4. Receiving an MPLS Echo Request
An LSR X that receives an MPLS echo request first parses the packet An LSR X that receives an MPLS echo request first parses the packet
to ensure that it is a well-formed packet, and that the TLVs that are to ensure that it is a well-formed packet, and that the TLVs that are
not marked "Ignore" are understood. If not, X SHOULD send an MPLS not marked "Ignore" are understood. If not, X SHOULD send an MPLS
echo reply with the Return Code set to "Malformed echo request echo reply with the Return Code set to "Malformed echo request
received" or "TLV not understood" (as appropriate), and the Subcode received" or "TLV not understood" (as appropriate), and the Subcode
set to zero. In the latter case, the misunderstood TLVs (only) are set to zero. In the latter case, the misunderstood TLVs (only) are
included in the reply. included in the reply.
If the echo request is good, X notes the interface I over which the If the echo request is good, X notes the interface I over which the
echo was received, and the label stack with which it came. echo was received, and the label stack with which it came.
X matches up the labels in the received label stack with the FECs X matches up the labels in the received label stack with the FECs
contained in the FEC stack. The matching is done beginning at the contained in the FEC stack. The matching is done beginning at the
bottom of both stacks, and working up. For reporting purposes the bottom of both stacks, and working up. For reporting purposes the
bottom of stack is consided to be stack-depth of 1. This is to bottom of stack is consided to be stack-depth of 1. This is to
establish an absolute reference for the case where the stack may have establish an absolute reference for the case where the stack may have
more labels than are in the FEC stack. more labels than are in the FEC stack.
If there are more FECs than labels, the extra FECs are assumed to If there are more FECs than labels, the extra FECs are assumed to
correspond to Implicit Null Labels. That is, extra Implicit Null correspond to Implicit Null Labels. Thus for the processing below,
Labels are added to the top of the received label stack and the stack there is never the case where there is a FEC with no corresponding
depth is set to the depth of the FEC stack. Thus for the processing label. Further the label operation associated with an assumed Null
below, there is never the case where there is a FEC with no Label is 'pop and continue processing'.
corresponding label. Further, the label operation associated with an
assumed Null Label is 'pop and continue processing'.
Note: in all the error codes listed in this draft a stack-depth of 0 Note: in all the error codes listed in this draft a stack-depth of 0
means "no value specified". This allows compatibility with existing means "no value specified". This allows compatibility with existing
implementations which do not use the Return Subcode field. implementations which do not use the Return Subcode field.
X sets a variable, call it current-stack-depth, to the number of X sets two variables, called FEC-stack-depth and Label-stack-depth,
labels in the received label stack. Processing now continues with to the number of labels in the received label stack. If the label-
the following steps: stack-depth is 0, assume there is one implicit null label and set
label-stack-depth to 1. Processing now continues with the following
steps:
1. Check if there is a FEC corresponding to the current-stack- Label_Validation:
depth. If there is, go to step 2. If not, check if the label is
valid on interface I. If it is, continue with step 4. Otherwise
X MUST send an MPLS echo reply with a Return Code 11, "No label
entry at stack-depth" and a Return Subcode set to current-stack-
depth.
2. Check the FEC at the current-stack-depth to determine what If the label at Label-stack-depth is valid, goto Label_Operation.
protocol would be used to advertise it. If it can determine that If not, set Best-return-code to 11, "No label entry at stack-depth"
no protocol associated with interface I, would have advertised a and Best-return-subcode to Label-stack-depth. Goto
FEC of that FEC-Type, X MUST send an MPLS echo reply with a Send_Reply_Packet.
Return Code 12, "Protocol not associated with interface at FEC
stack-depth" and a Return Subcode set to current-stack-depth.
3. Check that the mapping for the FEC at the current-stack-depth is Label_Operation:
the corresponding label.
If no mapping for the FEC exists, X MUST send an MPLS echo reply Switch on label operation.
with a Return Code 4, "Replying router has no mapping for the FEC
at stack-depth" and a Return Subcode set to current- stack-depth.
If a mapping is found, but the mapping is not the corresponding Case: Pop and Continue Processing (Note: this includes
label, X MUST send an MPLS echo reply with a Return Code 10, Explicit_Null and Router_Alert)
"Mapping for this FEC is not the given label at stack-depth" and
a Return Subcode set to current-stack-depth.
4. X determines the label operation. If the operation is to pop and If Label-stack-depth is greater than 1, decrement Label-stack-
continue processing, X checks the current-stack-depth. If it is depth and goto Label_Validation. Otherwise, set FEC-stack-depth
one, X MUST send an MPLS echo reply with a Return Code 3, to 1, set Best-return-code to 3 "Replying router is an egress for
"Replying router is an egress for the FEC at stack depth" and a the FEC at stack depth", set Best-return-subcode to 1 and goto
Return Subcode set to one. Otherwise, X decrements current-stack- Egress_Processing.
depth and goes back to step 1.
If the label operation is pop and switch based on the popped Case: Swap or Pop and Switch based on Popped Label
label, X then checks if it is valid to forward a labelled packet.
If it is, X MUST send an MPLS echo reply with a Return Code 8,
"Label switched at stack-depth" and a Return Subcode set to
current-stack-depth. If it is not valid to forward a labelled
packet, X MUST send an MPLS echo reply with a Return Code 9,
"Label switched but no MPLS forwarding at stack-depth" and a
Return Subcode set to current-stack-depth. This return code is
sent even if current-stack-depth is one.
If the label operation is swap, X MUST send an MPLS echo reply If the label operation is either swap or pop and switch based on
with a Return Code 8, "Label switched at stack-depth" and a the popped label, Best-return-code to 8, "Label switched at
Return Subcode set to current-stack-depth. stack-depth" and Best-return-subcode to Label-stack-depth.
If the MPLS echo request contains a downstream mapping TLV, and the If a Downstream Mapping TLV is present, a Downstream mapping TLVs
MPLS echo reply has either a Return Code of 8, or a Return Code of 9 SHOULD be created for each multipath.
with a Return Subcode of 1 then Downstream mapping TLVs SHOULD be
included for each multipath.
X uses the procedure in the next subsection to send the echo reply. Determine the output interface. If it is not valid to forward a
labelled packet on this interface, set Best-return-code to Return
Code 9, "Label switched but no MPLS forwarding at stack-depth"
and set Best-return-subcode to Label-stack-depth and goto
Send_Reply_Packet. (Note: this return code is set even if Label-
stack-depth is one.)
4.4. Sending an MPLS Echo Reply If no Downstream Mapping TLV is present, or the Downstream IP
Address is set to the All-Routers multicast address goto
Send_Reply_Packet.
Verify that the IP address, interface address and label stack
match the received interface and label stack. If not, set Best-
return-code to 5, "Downstream Mapping Mis-match". A Received
Interface and Label Stack TLV SHOULD be created. Goto
Send_Reply_Packet.
If the "Validate FEC Stack" flag is not set, goto
Send_Reply_Packet.
Locate the label at Label-stack-depth in the Downstream Labels
and set FEC-stack-depth to that depth. (Note: If the Downstream
Labels contain one or more Implicit Null labels, this may be at a
depth greater than Label-stack-depth.
If the depth of the FEC stack is greater than or equal to FEC-
stack-depth, Perform FEC Checking. If FEC-status is 2, set Best-
return-code to 10, "Mapping for this FEC is not the given label
at stack-depth".
If the return code is 1 set Best-return-code to FEC-return-code
and Best-return-subcode to FEC-stack-depth.
Goto Send_Reply_Packet.
Egress_Processing:
If no Downstream Mapping TLV is present, goto
Egress_FEC_Validation.
Verify that the IP address, interface address and label stack match
the received interface and label stack. If not, set Best-return-
code to 5, "Downstream Mapping Mis-match". A Received Interface
and Label Stack TLV SHOULD be created. Goto Send_Reply_Packet.
Egress_FEC_Validation:
Perform FEC checking. If FEC-status is 1, set Best-return-code
to FEC-code and Best-return-subcode to FEC-stack-depth. Goto
Send_Reply_Packet.
Increment FEC-stack-depth. If FEC-stack-depth is greater than
the number of FECs in the FEC-stack, goto Send_Reply_Packet. If
FEC-status is 0, increment Label-stack-depth. Goto
Egress_FEC_Validation.
Send_Reply_Packet:
Send an MPLS echo reply with a Return Code of Best-return-code,
and a Return Subcode of Best-return-subcode. Include any TLVs
created during the above process. The procedures for sending the
echo reply are found in the next subsection below.
FEC_Checking:
This routine accepts a FEC, Label, and Interface. It returns two
values, FEC-status and FEC-return-code, both of which are
initialized to 0.
If the FEC is the Nil FEC, check that Label is either
Explicit_Null or Router_Alert. If so return. Else
set FEC-return-code to 10, "Mapping for this FEC is not the given
label at stack-depth". Set FEC-status to 1 and return.
Check that the label mapping for FEC. If no mapping exists, set
FEC-return-code to Return 4, "Replying router has no mapping for
the FEC at stack-depth". Set FEC-status to 1. Return.
If the label mapping for FEC is Implicit Null, set FEC-status to
2. Goto Check_Protocol.
If the label mapping for FEC is Label, goto Check_Protocol. Else
set FEC-return-code to 10, "Mapping for this FEC is not the given
label at stack-depth". Set FEC-status to 1 and return.
Check_Protocol:
Check what protocol would be used to advertise FEC. If it can be
determined that no protocol associated with interface I would
have advertised a FEC of that FEC-Type, set FEC-return-code to
12, "Protocol not associated with interface at FEC stack-depth".
Set FEC-status to 1. Return.
4.5. Sending an MPLS Echo Reply
An MPLS echo reply is a UDP packet. It MUST ONLY be sent in response An MPLS echo reply is a UDP packet. It MUST ONLY be sent in response
to an MPLS echo request. The source IP address is a routable address to an MPLS echo request. The source IP address is a routable address
of the replier; the source port is the well-known UDP port for LSP of the replier; the source port is the well-known UDP port for LSP
ping. The destination IP address and UDP port are copied from the ping. The destination IP address and UDP port are copied from the
source IP address and UDP port of the echo request. The IP TTL is source IP address and UDP port of the echo request. The IP TTL is
set to 255. If the Reply Mode in the echo request is "Reply via an set to 255. If the Reply Mode in the echo request is "Reply via an
IPv4 UDP packet with Router Alert", then the IP header MUST contain IPv4 UDP packet with Router Alert", then the IP header MUST contain
the Router Alert IP option. If the reply is sent over an LSP, the the Router Alert IP option. If the reply is sent over an LSP, the
topmost label MUST in this case be the Router Alert label (1) (see topmost label MUST in this case be the Router Alert label (1) (see
skipping to change at page 26, line 25 skipping to change at page 35, line 41
most useful if the time-of-day clocks on the requestor and the most useful if the time-of-day clocks on the requestor and the
replier are synchronized). The FEC Stack TLV from the echo request replier are synchronized). The FEC Stack TLV from the echo request
MAY be copied to the reply. MAY be copied to the reply.
The replier MUST fill in the Return Code and Subcode, as determined The replier MUST fill in the Return Code and Subcode, as determined
in the previous subsection. in the previous subsection.
If the echo request contains a Pad TLV, the replier MUST interpret If the echo request contains a Pad TLV, the replier MUST interpret
the first octet for instructions regarding how to reply. the first octet for instructions regarding how to reply.
If the echo request contains a Downstream Mapping TLV, the replier If the replying router is the destination of the FEC, then Downstream
SHOULD compute its downstream routers and corresponding labels for Mapping TLVs SHOULD NOT be included in the echo reply.
the incoming label, and add Downstream Mapping TLVs for each one to
the echo reply it sends back.
4.5. Receiving an MPLS Echo Reply If the echo request contains a Downstream Mapping TLV, and the reply-
ing router is not the destination of the FEC, the replier SHOULD com-
pute its downstream routers and corresponding labels for the incoming
label, and add Downstream Mapping TLVs for each one to the echo reply
it sends back.
If the Downstream Mapping TLV contains multipath information requir-
ing more processing than the receiving router is willing to perform,
the responding router MAY choose to respond with only a subset of
multipaths contained in the Echo Request Downstream Map. (Note: The
originator of the echo request MAY send another echo request with the
multipath information that was not included in the reply.)
4.6. Receiving an MPLS Echo Reply
An LSR X should only receive an MPLS Echo Reply in response to an An LSR X should only receive an MPLS Echo Reply in response to an
MPLS Echo Request that it sent. Thus, on receipt of an MPLS Echo MPLS Echo Request that it sent. Thus, on receipt of an MPLS Echo
Reply, X should parse the packet to assure that it is well-formed, Reply, X should parse the packet to assure that it is well-formed,
then attempt to match up the Echo Reply with an Echo Request that it then attempt to match up the Echo Reply with an Echo Request that it
had previously sent, using the destination UDP port and the Sender's had previously sent, using the destination UDP port and the Sender's
Handle. If no match is found, then X jettisons the Echo Reply; Handle. If no match is found, then X jettisons the Echo Reply; oth-
otherwise, it checks the Sequence Number to see if it matches. Gaps erwise, it checks the Sequence Number to see if it matches. Gaps in
in the Sequence Number MAY be logged and SHOULD be counted. Once an the Sequence Number MAY be logged and SHOULD be counted. Once an
Echo Reply is received for a given Sequence Number (for a given UDP Echo Reply is received for a given Sequence Number (for a given UDP
port and Handle), the Sequence Number for subsequent Echo Requests port and Handle), the Sequence Number for subsequent Echo Requests
for that UDP port and Handle SHOULD be incremented. for that UDP port and Handle SHOULD be incremented.
If the Echo Reply contains Downstream Mappings, and X wishes to If the Echo Reply contains Downstream Mappings, and X wishes to
traceroute further, it SHOULD copy the Downstream Mappings into its traceroute further, it SHOULD copy the Downstream Mappings into its
next Echo Request (with TTL incremented by one). next Echo Request (with TTL incremented by one).
4.6. Issue with VPN IPv4 and IPv6 Prefixes 4.7. Issue with VPN IPv4 and IPv6 Prefixes
Typically, a LSP ping for a VPN IPv4 or IPv6 prefix is sent with a Typically, a LSP ping for a VPN IPv4 or IPv6 prefix is sent with a
label stack of depth greater than 1, with the innermost label having label stack of depth greater than 1, with the innermost label having
a TTL of 1. This is to terminate the ping at the egress PE, before a TTL of 1. This is to terminate the ping at the egress PE, before
it gets sent to the customer device. However, under certain it gets sent to the customer device. However, under certain circum-
circumstances, the label stack can shrink to a single label before stances, the label stack can shrink to a single label before the ping
the ping hits the egress PE; this will result in the ping terminating hits the egress PE; this will result in the ping terminating prema-
prematurely. One such scenario is a multi-AS Carrier's Carrier VPN. turely. One such scenario is a multi-AS Carrier's Carrier VPN.
To get around this problem, one approach is for the LSR that receives To get around this problem, one approach is for the LSR that receives
such a ping to realize that the ping terminated prematurely, and send such a ping to realize that the ping terminated prematurely, and send
back error code 13. In that case, the initiating LSR can retry the back error code 13. In that case, the initiating LSR can retry the
ping after incrementing the TTL on the VPN label. In this fashion, ping after incrementing the TTL on the VPN label. In this fashion,
the ingress LSR will sequentially try TTL values until it finds one the ingress LSR will sequentially try TTL values until it finds one
that allows the VPN ping to reach the egress PE. that allows the VPN ping to reach the egress PE.
4.7. Non-compliant Routers 4.8. Non-compliant Routers
If the egress for the FEC Stack being pinged does not support MPLS If the egress for the FEC Stack being pinged does not support MPLS
ping, then no reply will be sent, resulting in possible "false ping, then no reply will be sent, resulting in possible "false nega-
negatives". If in "traceroute" mode, a transit LSR does not support tives". If in "traceroute" mode, a transit LSR does not support LSP
LSP ping, then no reply will be forthcoming from that LSR for some ping, then no reply will be forthcoming from that LSR for some TTL,
TTL, say n. The LSR originating the echo request SHOULD try sending say n. The LSR originating the echo request SHOULD try sending the
the echo request with TTL=n+1, n+2, ..., n+k in the hope that some echo request with TTL=n+1, n+2, ..., n+k to probe LSRs further down
transit LSR further downstream may support MPLS echo requests and the path. In such a case, the echo request for TTL > n SHOULD be
reply. In such a case, the echo request for TTL>n MUST NOT have sent with Downstream Mapping TLV "Downstream IP Address" field set to
Downstream Mapping TLVs, until a reply is received with a Downstream the ALLROUTERs multicast address until a reply is received with a
Mapping. Downstream Mapping TLV. The Label Stack MAY be omitted from the
Downstream Mapping TLV. Further the "Validate FEC Stack" flag SHOULD
NOT be set until an ECHO REQUEST packet with a Downstream Mapping TLV
is received.
5. References
Normative References Normative References
[IANA] Narten, T. and H. Alvestrand, "Guidelines for IANA [IANA] Narten, T. and H. Alvestrand, "Guidelines for IANA
Considerations", BCP 26, RFC 2434, October 1998. Considerations", BCP 26, RFC 2434, October 1998.
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[LABEL-STACK] Rosen, E., et al, "MPLS Label Stack Encoding", RFC [LABEL-STACK] Rosen, E., et al, "MPLS Label Stack Encoding",
3032, January 2001. RFC 3032, January 2001.
[RSVP] Braden, R. (Editor), et al, "Resource ReSerVation protocol [RSVP] Braden, R. (Editor), et al, "Resource ReSerVation
(RSVP) -- Version 1 Functional Specification," RFC 2205, Protocol (RSVP) -- Version 1 Functional
September 1997. Specification," RFC 2205, September 1997.
[RSVP-REFRESH] Berger, L., et al, "RSVP Refresh Overhead Reduction [RSVP-REFRESH] Berger, L., et al, "RSVP Refresh Overhead Reduction
Extensions", RFC 2961, April 2001. Extensions", RFC 2961, April 2001.
[RSVP-TE] Awduche, D., et al, "RSVP-TE: Extensions to RSVP for LSP [RSVP-TE] Awduche, D., et al, "RSVP-TE: Extensions to RSVP for
tunnels", RFC 3209, December 2001. LSP tunnels", RFC 3209, December 2001.
Informative References Informative References
[ICMP] Postel, J., "Internet Control Message Protocol", RFC 792. [ICMP] Postel, J., "Internet Control Message Protocol",
RFC 792.
[LDP] Andersson, L., et al, "LDP Specification", RFC 3036, January [LDP] Andersson, L., et al, "LDP Specification", RFC 3036,
2001. January 2001.
Security Considerations 6. Security Considerations
There are at least two approaches to attacking LSRs using the There are at least two approaches to attacking LSRs using the mecha-
mechanisms defined here. One is a Denial of Service attack, by nisms defined here. One is a Denial of Service attack, by sending
sending MPLS echo requests/replies to LSRs and thereby increasing MPLS echo requests/replies to LSRs and thereby increasing their work-
their workload. The other is obfuscating the state of the MPLS data load. The other is obfuscating the state of the MPLS data plane
plane liveness by spoofing, hijacking, replaying or otherwise liveness by spoofing, hijacking, replaying or otherwise tampering
tampering with MPLS echo requests and replies. with MPLS echo requests and replies.
Authentication will help reduce the number of seemingly valid MPLS Authentication will help reduce the number of seemingly valid MPLS
echo requests, and thus cut down the Denial of Service attacks; echo requests, and thus cut down the Denial of Service attacks;
beyond that, each LSR must protect itself. beyond that, each LSR must protect itself.
Authentication sufficiently addresses spoofing, replay and most Authentication sufficiently addresses spoofing, replay and most tam-
tampering attacks; one hopes to use some mechanism devised or pering attacks; one hopes to use some mechanism devised or suggested
suggested by the RPSec WG. It is not clear how to prevent hijacking by the RPSec WG. It is not clear how to prevent hijacking (non-
(non-delivery) of echo requests or replies; however, if these delivery) of echo requests or replies; however, if these messages are
messages are indeed hijacked, LSP ping will report that the data indeed hijacked, LSP ping will report that the data plane isn't work-
plane isn't working as it should. ing as it should.
It doesn't seem vital (at this point) to secure the data carried in It doesn't seem vital (at this point) to secure the data carried in
MPLS echo requests and replies, although knowledge of the state of MPLS echo requests and replies, although knowledge of the state of
the MPLS data plane may be considered confidential by some. the MPLS data plane may be considered confidential by some.
5. IANA Considerations 7. IANA Considerations
The TCP and UDP port number 3503 has been allocated by IANA for LSP The TCP and UDP port number 3503 has been allocated by IANA for LSP
echo requests and replies. echo requests and replies.
The following sections detail the new name spaces to be managed by The following sections detail the new name spaces to be managed by
IANA. For each of these name spaces, the space is divided into IANA. For each of these name spaces, the space is divided into
assignment ranges; the following terms are used in describing the assignment ranges; the following terms are used in describing the
procedures by which IANA allocates values: "Standards Action" (as procedures by which IANA allocates values: "Standards Action" (as
defined in [IANA]); "Expert Review" and "Vendor Private Use". defined in [IANA]); "Expert Review" and "Vendor Private Use".
Values from "Expert Review" ranges MUST be registered with IANA, and Values from "Expert Review" ranges MUST be registered with IANA, and
MUST be accompanied by an Experimental RFC that describes the format MUST be accompanied by an Experimental RFC that describes the format
and procedures for using the code point; the actual assignment is and procedures for using the code point; the actual assignment is
made during the IANA actions for the RFC. made during the IANA actions for the RFC.
Values from "Vendor Private" ranges MUST NOT be registered with IANA; Values from "Vendor Private" ranges MUST NOT be registered with IANA;
however, the message MUST contain an enterprise code as registered however, the message MUST contain an enterprise code as registered
with the IANA SMI Network Management Private Enterprise Codes. For with the IANA SMI Network Management Private Enterprise Codes. For
each name space that has a Vendor Private range, it must be specified each name space that has a Vendor Private range, it must be specified
where exactly the SMI Enterprise Code resides; see below for where exactly the SMI Enterprise Code resides; see below for exam-
examples. In this way, several enterprises (vendors) can use the ples. In this way, several enterprises (vendors) can use the same
same code point without fear of collision. code point without fear of collision.
5.1. Message Types, Reply Modes, Return Codes 7.1. Message Types, Reply Modes, Return Codes
It is requested that IANA maintain registries for Message Types, It is requested that IANA maintain registries for Message Types,
Reply Modes, Return Codes and Return Subcodes. Each of these can Reply Modes, Return Codes and Return Subcodes. Each of these can
take values in the range 0-255. Assignments in the range 0-191 are take values in the range 0-255. Assignments in the range 0-191 are
via Standards Action; assignments in the range 192-251 are made via via Standards Action; assignments in the range 192-251 are made via
Expert Review; values in the range 252-255 are for Vendor Private Expert Review; values in the range 252-255 are for Vendor Private
Use, and MUST NOT be allocated. Use, and MUST NOT be allocated.
If any of these fields fall in the Vendor Private range, a top-level If any of these fields fall in the Vendor Private range, a top-level
Vendor Enterprise Code TLV MUST be present in the message. Vendor Enterprise Code TLV MUST be present in the message.
5.2. TLVs 7.2. TLVs
It is requested that IANA maintain registries for the Type field of It is requested that IANA maintain registries for the Type field of
top-level TLVs as well as for sub-TLVs. The valid range for each of top-level TLVs as well as for sub-TLVs. The valid range for each of
these is 0-65535. Assignments in the range 0-16383 and 32768-49161 these is 0-65535. Assignments in the range 0-16383 and 32768-49161
are made via Standards Action as defined in [IANA]; assignments in are made via Standards Action as defined in [IANA]; assignments in
the range 16384-31743 and 49162-64511 are made via Expert Review (see the range 16384-31743 and 49162-64511 are made via Expert Review (see
below); values in the range 31744-32746 and 64512-65535 are for below); values in the range 31744-32746 and 64512-65535 are for Ven-
Vendor Private Use, and MUST NOT be allocated. dor Private Use, and MUST NOT be allocated.
If a TLV or sub-TLV has a Type that falls in the range for Vendor If a TLV or sub-TLV has a Type that falls in the range for Vendor
Private Use, the Length MUST be at least 4, and the first four octets Private Use, the Length MUST be at least 4, and the first four octets
MUST be that vendor's SMI Enterprise Code, in network octet order. MUST be that vendor's SMI Enterprise Code, in network octet order.
The rest of the Value field is private to the vendor. The rest of the Value field is private to the vendor.
Acknowledgments 8. Acknowledgments
This document is the outcome of many discussions among many people, This document is the outcome of many discussions among many people,
that include Manoj Leelanivas, Paul Traina, Yakov Rekhter, Der-Hwa that include Manoj Leelanivas, Paul Traina, Yakov Rekhter, Der-Hwa
Gan, Brook Bailey, Eric Rosen, Ina Minei, Shivani Aggarwal and Vansom Gan, Brook Bailey, Eric Rosen, Ina Minei, Shivani Aggarwal and Vanson
Lim. Lim.
The description of the Multipath Information sub-field of the The description of the Multipath Information sub-field of the Down-
Downstream Mapping TLV was adapted from text suggested by Curtis stream Mapping TLV was adapted from text suggested by Curtis Vil-
Villamizar. lamizar.
Appendix A. Appendix
This appendix specifies non-normative aspects of detecting MPLS data This appendix specifies non-normative aspects of detecting MPLS data
plane liveness. plane liveness.
5.1. CR-LDP FEC A.1. CR-LDP FEC
This section describes how a CR-LDP FEC can be included in an Echo This section describes how a CR-LDP FEC can be included in an Echo
Request using the following FEC subtype: Request using the following FEC subtype:
Sub-Type # Length Value Field Sub-Type # Length Value Field
---------- ------ ------------- ---------- ------ -------------
5 6 CR-LDP LSP ID 5 6 CR-LDP LSP ID
The value consists of the LSPID of the LSP being pinged. An LSPID is The value consists of the LSPID of the LSP being pinged. An LSPID is
a four octet IPv4 address (a local address on the ingress LSR, for a four octet IPv4 address (a local address on the ingress LSR, for
skipping to change at page 31, line 5 skipping to change at page 40, line 32
per LSP on a given ingress LSR. per LSP on a given ingress LSR.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ingress LSR Router ID | | Ingress LSR Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must Be Zero | LSP ID | | Must Be Zero | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.2. Downstream Mapping for CR-LDP A.2. Downstream Mapping for CR-LDP
If a label in a Downstream Mapping was learned via CR-LDP, the If a label in a Downstream Mapping was learned via CR-LDP, the Proto-
Protocol field in the Mapping TLV can use the following entry: col field in the Mapping TLV can use the following entry:
Protocol # Signaling Protocol Protocol # Signaling Protocol
---------- ------------------ ---------- ------------------
5 CR-LDP 5 CR-LDP
Authors' Address Authors' Address
Kireeti Kompella Kireeti Kompella
Juniper Networks Juniper Networks
1194 N.Mathilda Ave 1194 N.Mathilda Ave
Sunnyvale, CA 94089 Sunnyvale, CA 94089
Email: kireeti@juniper.net Email: kireeti@juniper.net
George Swallow George Swallow
Cisco Systems Cisco Systems
1414 Massachusetts Ave, 1414 Massachusetts Ave,
Boxborough, MA 01719 Boxborough, MA 01719
Phone: +1 978 936 1398 Phone: +1 978 936 1398
Email: swallow@cisco.com Email: swallow@cisco.com
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