wdiff draft-ietf-mpls-lsp-ping-relay-reply-02.txt draft-ietf-mpls-lsp-ping-relay-reply-03.txt

Network Working Group J. Luo, Ed.
Internet-Draft ZTE
Updates: 4379 (if approved) L. Jin, Ed.
Intended status: Standards Track
Expires: August 18, October 4, 2014 T. Nadeau, Ed.
Lucidvision
G. Swallow, Ed.
Cisco
February 14,
April 2, 2014

Relayed Echo Reply mechanism for LSP Ping
draft-ietf-mpls-lsp-ping-relay-reply-02
draft-ietf-mpls-lsp-ping-relay-reply-03

Abstract

In some inter autonomous system (AS) and inter-area deployment
scenarios for Label RFC 4379 "Label Switched Path (LSP) Ping and Traceroute,
Traceroute", a replying LSR may not have the available route to the
initiator, and the Echo Reply message sent to the initiator would be
discarded resulting in false negatives or complete failure of
operation of LSP Ping and Traceroute. This document describes
extensions to LSP Ping mechanism to enable the replying Label
Switching Router (LSR) to have the capability to relay the Echo
Response by a set of routable intermediate nodes to the initiator.
This document updates RFC 4379.

Status of this Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
1.1. Conventions Used in This Document . . . . . . . . . . . . 3 4
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
3. Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6
3.1. Relayed Echo Reply message . . . . . . . . . . . . . . . . 5 6
3.2. Relay Node Address Stack . . . . . . . . . . . . . . . . . 5 6
3.3. New Return Code . . . . . . . . . . . . . . . . . . . . . 7 8
4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8
4.1. Sending an Echo Request . . . . . . . . . . . . . . . . . 7 8
4.2. Receiving an Echo Request . . . . . . . . . . . . . . . . 7 8
4.3. Originating an Relayed Echo Reply . . . . . . . . . . . . 8 9
4.4. Relaying an Relayed Echo Reply . . . . . . . . . . . . . . 9
4.5. Sending an Echo Reply . . . . . . . . . . . . . . . . . . 9 10
4.6. Receiving an Echo Reply . . . . . . . . . . . . . . . . . 9 10
5. LSP Ping Relayed Echo Reply Example . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 12
7. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 13
8.1. New Message Type . . . . . . . . . . . . . . . . . . . . . 12 13
8.2. New TLV . . . . . . . . . . . . . . . . . . . . . . . . . 12 13
8.3. New Return Code . . . . . . . . . . . . . . . . . . . . . 12 13
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 13 14
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13 14
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 14
11.1. Normative References . . . . . . . . . . . . . . . . . . . 13 14
11.2. Informative References . . . . . . . . . . . . . . . . . . 13 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 15

1. Introduction

This document describes the extensions to the Label Switched Path
(LSP) Ping as specified in [RFC4379], by adding a relayed echo reply
mechanism which could be used to detect data plane failures in for the
inter autonomous system (AS) and inter-area LSPs. The extensions are
to update the [RFC4379]. Without this extension, these extensions, the ping
functionality provided by [RFC4379] would fail in many deployed
inter-AS scenarios, since the replying LSR in one AS may not have the
available route to the initiator in the other AS. The mechanism in
this draft document defines a new message type referred as "Relayed Echo
Reply message", and a new TLV referred as "Relay Node Address Stack
TLV".

1.1. Conventions Used in This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

2. Motivation

LSP Ping [RFC4379] defines a mechanism to detect the data plane
failures and localize faults. The mechanism specifies that the Echo
Reply should be sent back to the initiator usig using an UDP packet with
the IPv4/ IPv6 address of the originating LSR. This works in
administrative domains allowing where IP address addresses reachability are allowed
among LSRs, and routing every LSR is able to route back to the originating
LSR. However, in practice, this is often not the case due to intra-provider intra-
provider routing policy, route hiding, and network address
translation at autonomous system border routers (ASBR), and
etc. (ASBR). In fact, it
is almost uniformly the case that in inter-AS scenarios, it is not
allowed the distribution or direct routing to the IP addresses of any
of the nodes other than the ASBR. ASBR in another AS.

Figure 1 demonstrates a case where one LSP is set up between PE1 and
PE2. If private addresses were in use within AS2, AS1, a traceroute from
PE1 directed to PE2 could fail if the fault exists somewhere between
ASBR2 and PE2. Because P2 cannot forward packets back to PE1 given
that it is a private address within AS1. In this case, PE1 would
detect a path break, as the Echo Request Reply messages would not be sent
back; however,
received. Then localization of the actual fault would not be
possible.

+-------+ +-------+ +------+ +------+ +------+ +------+
| | | | | | | | | | | |
| PE1 +---+ P1 +---+ ASBR1+---+ ASBR2+---+ P2 +---+ PE2 |
| | | | | | | | | | | |
+-------+ +-------+ +------+ +------+ +------+ +------+
<---------------AS1-------------><---------------AS2------------>
<---------------------------- LSP ------------------------------>

Figure 1: Simple Inter-AS LSP Configuration

A second example that illustrates how [RFC4379] would be insufficient
would be the inter-area situation in a Seamless seamless MPLS architecture
[I-D.ietf-mpls-seamless-mpls] as shown below in Figure 2. In this
example P nodes the LSRs in the core network would not have IP reachable route to
any of the ANs. When tracing an LSP from one AN to the remote AN,
the LSR1/LSR2 node could not make a response to the Echo Request
either, like the P2 node in the inter-AS scenario in Figure 1.

+-------+ +-------+ +------+ +------+
| | | | | | | |
+--+ AGN11 +---+ AGN21 +---+ ABR1 +---+ LSR1 +--> to AGN
/ | | /| | | | | |
+----+/ +-------+\/ +-------+ +------+ /+------+
| AN | /\ \/
+----+\ +-------+ \+-------+ +------+/\ +------+
\ | | | | | | \| |
+--+ AGN12 +---+ AGN22 +---+ ABR2 +---+ LSR2 +--> to AGN
| | | | | | | |
+-------+ +-------+ +------+ +------+
static route ISIS L1 LDP ISIS L2 LDP
<-Access-><--Aggregation Domain--><---------Core--------->

Figure 2: Seamless MPLS Architecture

This document describes extensions to the LSP Ping mechanism to
facilitate a response from the replying LSR, by defining a simple
mechanism that uses the a relay node (e.g, ASBR) to relay the message
back to the initiator. This approach will work because every Every designated or learned relay node must
have an IP route back to the next relay node or to the initiator. Using a
recursive approach, relay node could relay the message to the next
relay node until the initiator is reached.

3. Extensions

[RFC4379] describes the basic MPLS LSP Ping mechanism, which defines
two message types, Echo Request and Echo Reply message. This draft
document defines a new message, Relayed Echo Reply message. This new
message is used to replace Echo Reply message which is sent from the
replying LSR to a relay node or from a relay node to another relay
node.

A new TLV named Relay Node Address Stack TLV is defined in this
draft,
document, to carry the IP addresses of the possible relay nodes for
the replying LSR.

In addition, a new Return Code is defined to notify the initiator
that the packet length was is exceeded unexpected by the Relay Node
Address Stack TLV.

It should be noted that this document focuses only on detecting the
LSP which is set up using a uniform type of IP address. address family type. That is,
all hops between the source and destination node use one the same address
family type of for their LSP ping control planes. This does not
preclude nodes that support both IPv6 and IPv4 addresses
simultaneously, but the entire path must be addressable using only
one address family type. Supporting for mixed IPv4-only and IPv6-only IPv6-
only is beyond the scope of this document.

3.1. Relayed Echo Reply message

The Relayed Echo Reply message is a UDP packet, and the UDP payload
has the same format with Echo Request/Reply message. A new message
type is requested from IANA.

New Message Type:
Value Meaning
----- -------
TBD MPLS Relayed Echo Reply

The use of TCP and UDP port number 3503 is described in [RFC4379] and
has been allocated in [RFC4379] by IANA for LSP Ping messages. The Relayed Echo
Reply message will use the same port number.

3.2. Relay Node Address Stack

The Relay Node Address Stack TLV is an optional TLV. It MUST be
carried in the Echo Request, Echo Reply and Relayed Echo Reply
messages if the echo reply relayed mechanism described in this draft
document is required. Figure 3 illustrates the TLV 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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Initiator Source Port | Number of Relayed Addresses |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Stack of Relayed Addresses ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: Relay Node Address Stack TLV

- Type: to be assigned by IANA. A suggested value is should be assigned from
32768-49161 as suggested by RFC4379 [RFC4379] Section 3.

- Length: The Length the length of the Value value field in octets.

- Initiator Source Port: The the source UDP port that the initiator
sends the Echo Request message, and also the port that is expected
to receive the Echo Reply message.

- Number of Relayed Addresses: An an integer indicating the number of
relayed addresses in the stack.

- Stack of Relayed Addresses: A a list of relay node addresses.

The format of each relay node address is as below:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Type | Address Length| Reserved |K|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Relayed Address (0, 4, or 16 octects) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type# Address Type Address Length
---- ------------ ------------
0 Unspecified 0
1 IPv4 4
2 IPv6 16

Reserved: This field is reserved for future use and MUST be set to zero.

K bit: If if the K bit is set to 1, then this sub-TLV SHOULD MUST be kept in
Relay Node Address Stack, SHOULD not be deleted in Stack during TLV compress process
of described in
section 4.2. The K bit may be set by ASBRs which whose address would be
kept in the stack if necessary.

If the K bit is set to 0, then this sub-TLV SHOULD be processed
normally according to section 4.2.

Relayed Address: This this field specifies the node address, either IPv4
or IPv6.

3.3. New Return Code

A new Return Code is used by the replying LSR to notify the initiator
that the packet length was is exceeded unexpected by the Relay Node
Address Stack TLV.

New Return Code:
Value Meaning
----- -------
TBD Response Packet length was exceeded by the Relay Node
Address Stack TLV unexpected

4. Procedures

4.1. Sending an Echo Request

In addition to the procedures described in Section section 4.3 of [RFC4379],
a Relay Node Address Stack TLV MUST be carried in the Echo Request
message for to facilitate the relay functionality.

When the Echo Request is first sent by initiator supporting these
extensions, the initiator, a Relay Node
Address Stack TLV with the initiator address in the stack and its
source UDP port MUST be included. That will ensure that the first
relay node address in the stack will always be the initiator address.

For the subsequent Echo Request messages, the initiator would copy
the Relay Node Address Stack TLV from the received Echo Reply
message.

4.2. Receiving an Echo Request

In addition to the processes in Section section 4.4 of [RFC4379], the
procedures of the Relay Node Address Stack TLV are defined here.

Upon receiving a Relay Node Address Stack TLV of the Echo Request
message, the receiver MUST check the addresses of the stack in
sequence from top to bottom (the first address in the stack ==== will be
the first one to be checked), to find out the first public routable
IP address. Those address entries behind of the first routable IP
address in the address list with K bit set to 0 MUST be deleted, and
the address entry of the replying LSR MUST be added at the bottom of
the stack. Those address entries with K bit set to 1 MUST be kept in
the stack. The updated Relay Node Address Stack TLV MUST be carried
in the response message.

If the replying LSR wishes is configured to hide its routable address
information, the address entry added in the stack SHOULD be a blank
entry with Address Type set to unspecified. The blank address entry
in the receiving Echo Request SHOULD be treated as an unroutable
address entry.

If the packet length was exceeded unexpectedly by the Relay Node
Address Stack TLV, the TLV SHOULD be returned back unchanged in the
echo response
Echo Reply message. And the new return code in section 3.3 SHOULD help be
used to notify the initiator of the situation.

If the first routable IP address is the first address in the stack,
the replying LSR SHOULD respond an Echo Reply message to the
initiator.

If the first routable IP address is of an intermediate node, other than
the first address in the stack, the replying LSR SHOULD send an a
Relayed Echo Reply instead of an Echo Reply in as a response.

An LSR not recognize the Relay Node Address Stack TLV, SHOULD ignore
it according to section 3 of RFC4379. [RFC4379].

4.3. Originating an Relayed Echo Reply

When the replying LSR received receives an Echo Request with the initiator first IP
address in the Relay Node Address Stack TLV is IP unroutable, the
replying LSR SHOULD send an a Relayed Echo Reply message to the first
routable intermediate node. The processing of Relayed Echo Reply is
the same with the procedure of the Echo Reply described in Section
4.5 of RFC4379, [RFC4379], except the destination IP address and the
destination UDP port of the message part. port. The destination IP address of the Relayed Echo
Reply is set to the first routable IP address from the Relay Node
Address Stack TLV, and both the source and destination UDP port is
set to 3503.

4.4. Relaying an Relayed Echo Reply

Upon receiving an Relayed Echo Reply message with its own address as
the destination address in the IP header, the relay node should SHOULD check
the address items in Relay Node Address Stack TLV in sequence from
top to down, and find the first routable node address.

If the first routable address is the top one of the address list,
e.g, the initiator address, the relay node SHOULD send an Echo Reply
message to the initiator containing the same payload with the Relayed
Echo Reply message received. See section 4.5 for detail.

If the first routable address is not the top one of the address list,
e.g, another intermediate relay node, the relay node SHOULD send an
Relayed Echo Reply message to this relay node with the payload
unchanged.

Note, the replying LSR SHOULD send a Relayed Echo Reply message to
the first relay node found in Relay Node Address Stack TLV that is
routable by the router. The routable address MUST be located before
the source IP address of the received Relayed Echo Reply which must
be also in the stack, otherwise the Relayed Echo Reply should not be
sent, so as to avoid potential loop.

4.5. Sending an Echo Reply

The Echo Reply is sent in two cases:

1. When the replying LSR received receives an Echo Request with the initiator first IP
address in the Relay Node Address Stack TLV is IP routable, the replying
LSR would send an Echo Reply to the initiator. In addition to the
procedure of the Echo Reply described in Section 4.5 of
RFC4379, [RFC4379],
the Relay Node Address Stack TLV would be carried in the Echo Reply.

2. When the intermediate relay node received an receives a Relayed Echo Reply
with the initiator first IP address in the Relay Node Address Stack TLV IP
routable, the intermediate relay node would send the Echo Reply to
the initiator with the UDP payload unchanged other than the Message
Type
field. field (change from type of Relayed Echo Reply to Echo Reply).
The destination IP address of the Echo Reply is set to the
initiator first IP address,
address in the stack, and the destination UDP port would be copied
from the Initiator Source Port field of the Relay Node Address Stack
TLV. The source UDP port should be 3503.

4.6. Receiving an Echo Reply

In addition to the processes in Section 4.6 of [RFC4379], the
initiator would copy the Relay Node Address Stack TLV received in the
Echo Reply to the next Echo Request.

5. LSP Ping Relayed Echo Reply Example

Considering the inter-AS scenario in Figure 4 below.

Figure 4: Example Inter-AS LSP

In the example, an LSP has been created between PE1 to PE2. When
performing LSP traceroute on the LSP, the first Echo Request sent by
PE1 with outter-most outer-most label TTL=1, contains the Relay Node Address
Stack TLV with the only address of PE1. PE1's address.

After processed by P1, P1's address will be added in the Relay Node
Address Stack TLV address list following PE1's address in the Echo
Reply.

PE1 copies the Relay Node Address Stack TLV into the next Echo
Request when receiving the Echo Reply.

Upon receiving the Echo Request, ASBR1 checks the address list in the
Relay Node Address Stack TLV in sequence, and finds out that PE1 PE1's
address is routable. Then deletes P1 P1's address, and adds its own
address following PE1 address. As a result, there would be PE1 PE1's
address followed by ASBR1 ASBR1's address in the Relay Node Address Stack
TLV of the Echo Reply sent by ASBR1.

PE1 then sends an Echo Request with outer-most label TTL=3,
containing the Relay Node Address Stack TLV copied from the received
Echo Reply message. Upon receiving the Echo Request message, ASBR2
checks the address list in the Relay Node Address Stack TLV in
sequence, and finds out that PE1 PE1's address is IP route unreachable,
and
ASBR1 ASBR1's address is the first routable one in the Relay Node
Address Stack TLV. ASBR2 adds its address as the last address item
following
ASBR1 ASBR1's address in Relay Node Address Stack TLV, sets ASBR1
ASBR1's address as the destination address of the Relayed Echo Reply,
and sends the Relayed Echo Reply to ASBR1.

Upon receiving the Relayed Echo Reply from ASBR2, ASBR1 checks the
address list in the Relay Node Address Stack TLV in sequence, and
finds out that PE1 PE1's address is first routable one in the address
list. Then ASBR1 send sends an Echo Reply to PE1 with the payload of the
received Relayed Echo Reply no changes other than the Message Type
field.

For the Echo Request with outer-most label TTL=4, P2 checks the
address list in the Relay Node Address Stack TLV in sequence, and
finds out that both PE1 PE1's and ASBR1 ASBR1's addresses are not IP routable,
and
ASBR2 ASBR2's address is the first routable address. And Then P2 would send sends an
Relayed Echo Reply to ASBR2 with the Relay Node Address Stack TLV of
containing four addresses, PE1, ASBR1, ASBR2 PE1's, ASBR1's, ASBR2's and P2 P2's address
in sequence.

Then according to the process described in section 4.4, ASBR2 would
send sends
the Relayed Echo Reply to ASBR1. Upon receiving the Relayed Echo
Reply, ASBR1 would send sends an Echo Reply to PE1 as PE1 address which is routable. And as
relayed by ASBR2 and ASBR1, the echo response Echo Reply would finally be sent to
the initiator PE1.

For the Echo Request with outer-most label TTL=5, the echo response Echo Reply
would relayed to PE1 by ASBR2 and ASBR1, similar to the case of
TTL=4.

The Echo Reply from the replying node which has no IP reachable route
to the initiator is finally transmitted to the initiator by multiple
relay nodes.

6. Security Considerations

The Relayed Echo Reply mechanism for LSP Ping creates an increased
risk of DoS by putting the IP address of a target router in the Relay
Node Address Stack. These messages then could be used to attack the
control plane of an LSR by overwhelming it with these packets. A
rate limiter SHOULD be applied to the well-known UDP port on the
relay node as suggested in RFC4379. [RFC4379]. The node which acts as a relay
node SHOULD validate the relay reply against a set of valid source
addresses and discard packets from untrusted border router addresses.
An implementation SHOULD provide such filtering capabilities.

If an operator wants to obscure their nodes, it is RECOMMENDED that
they may replace the replying node address that originated the Echo
Reply with blank address in Relay Node Address Stack TLV.

Other security considerations discussed in [RFC4379], are also
applicable to this document.

7. Backward Compatibility

When one of the nodes along the LSP does not support the mechanism
specified in this draft, document, the node will ignore the Relay Node
Address Stack TLV as described in section 4.2. Then the initiator
may not receive the Relay Node Address Stack TLV in Echo Reply
message from that node. In this case, an indication should be
reported to the operator, and the Relay Node Address Stack TLV in the
next Echo Request message should be copied from the previous Echo
Request, and continue the ping process. If the node described above
is located between the initiator and the first relay node, the ping
process could continue without interruption.

8. IANA Considerations

IANA is requested to assign one new Message Type, one new TLV and one
new Return Code.

8.1. New Message Type

New Message Type:

This document requires allocation of one new message type from
"Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs)
Ping Parameters" registry, the "Message Type" registry:

Value Meaning
----- -------
TBD MPLS Relayed Echo Reply

The value should be assigned from the "Standards Action" range
(0-191), and using the lowest free value within this range.

8.2. New TLV

New TLV: Routable Relay Node Address

This document requires allocation of one new TLV from "Multi-Protocol
Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters"
registry, the "TLVs" registry:

Type Meaning
---- --------
TBD Relay Node Address Stack TLV

A suggested value is should be assigned from 32768-49161 "Standards Action" range
(32768-49161) as suggested by
RFC4379 [RFC4379] Section 3. 3, using the first
free value within this range.

8.3. New Return Code

New Return Code:

This document requires allocation of one new return code from "Multi-
Protocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping
Parameters" registry, the "Return Codes" registry:

Value Meaning
----- -------
TBD Response Packet length was exceeded unexpected by the Relay
Node Address Stack TLV unexpected

The value should be assigned from the "Standards Action" range
(0-191), and using the lowest free value within this range.

9. Acknowledgement

The authors would like to thank Carlos Pignataro, Xinwen Jiao, Manuel
Paul, Loa Andersson, Wim Henderickx, Mach Chen, Thomas Morin and
Gregory Mirsky for their valuable comments and suggestions.

10. Contributors

Ryan Zheng
JSPTPD
371, Zhongshan South Road
Nanjing, 210006, China
Email: ryan.zhi.zheng@gmail.com

11. References

11.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.

11.2. Informative References

[I-D.ietf-mpls-seamless-mpls]
Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz,
M., and D. Steinberg, "Seamless MPLS Architecture",
draft-ietf-mpls-seamless-mpls-05
draft-ietf-mpls-seamless-mpls-06 (work in progress),
January
February 2014.

Authors' Addresses

Jian Luo (editor)
ZTE
50, Ruanjian Avenue
Nanjing, 210012, China

Email: luo.jian@zte.com.cn

Lizhong Jin (editor)
Shanghai, China

Email: lizho.jin@gmail.com

Thomas Nadeau (editor)
Lucidvision

Email: tnadeau@lucidvision.com

George Swallow (editor)
Cisco
300 Beaver Brook Road
Boxborough , MASSACHUSETTS 01719, USA

Email: swallow@cisco.com