wdiff draft-ietf-mpls-cr-ldp-00.txt draft-ietf-mpls-cr-ldp-01.txt

MPLS Working Group L. Andersson, A. Fredette, B. Jamoussi Bilel Jamoussi, Editor
Internet Draft Nortel Networks
Expiration Date: July August 1999

February 1999
R. Callon
IronBridge Networks

P. Doolan
Ennovate Networks

N. Feldman
IBM Corp

E. Gray
Lucent Technologies

J. Halpern
Newbridge Networks

J. Heinanen
Telia Finland

T. E. Kilty
Northchurch Communications

A. G. Malis
Ascend Communications, Inc.

M. Girish
SBC Technology Resources, Inc.

K. Sundell
Ericsson

P. Vaananen
Nokia Telecommunications

T. Worster
General DataComm, Inc.

L. Wu, R. Dantu
Alcatel

January 1998

Constraint-Based LSP Setup using LDP

draft-ietf-mpls-cr-ldp-00.txt

draft-ietf-mpls-cr-ldp-01.txt

Status of this Memo

This document is an Internet-Draft. Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.

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CR-LDP Specification - 2 - Exp. Apr 1999 documents of the Internet Engineering
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Abstract

Label Distribution Protocol (LDP) is defined in [LDP] for
distribution of labels inside one MPLS domain. One of the most
important services that may be offered using MPLS in general and LDP
in particular is support for constraint-based routing of traffic
across the routed network. Constraint-based routing offers the
opportunity to extend the information used to setup paths beyond what
is available for the routing protocol. For instance, an LSP can be
setup based on an explicit route constraint, a Service Class (SC)
constraint, or both. constraints, QoS constraints, and
others. Constraint-based routing (CR) and is a mechanism used to meet
Traffic Engineering requirements that have been proposed by [FRAME],
[ARCH] and [TER]. These requirements may be met by extending LDP for
support of constraint-based routed label switched paths (CRLSPs).

CR-LDP Specification - 2 - Exp. August 1999

Other uses exist for CRLSPs as well ([VPN1] ([VPN1], [VPN2] and [VPN2]). [VPN3]).

This draft specifies mechanisms and TLVs for support of CRLSPs using
LDP. The Explicit Route object and procedures are extracted from
[ER].

Table of Contents

1. Introduction

The need for constraint-based routing (CR) in MPLS has been explored
elsewhere [ARCH], [FRAME], ......................................... 3
2. Constraint-based Routing Overview .................... 3
2.1 Strict and [TER]. Loose Explicit routing is a subset
of the more general constraint-based routing function. At the MPLS WG
meeting held during the Washington IETF there was consensus that LDP
should support explicit routing of LSPs with provision for indication
of associated (forwarding) priority. In the Chicago meeting, the
decision was made that support for explicit path setup in LDP will be
moved to a separate document. This document provides that support. We
propose an end-to-end setup mechanism of a constraint-based routed
LSP (CRLSP) initiated by the ingress LSR. We also specify mechanisms
to provide means for reservation of resources for the explicitly
routed LSP.

We introduce TLVs and procedures that provide support for:

CR-LDP Specification - 3 - Exp. Apr 1999

- Strict and Loose Explicit Routing
- Specification of Service Class
- Specification of Routes ..................... 4
2.2 Traffic Parameters
- Characteristics .............................. 4
2.3 Pre-emption .......................................... 5
2.4 Route Pinning
- CRLSP bumping though setup/holding priority
- Handling Failures

2. CRLSP Overview

CRLSP over LDP Specification is designed with several goals in mind:

1. Meet the requirements outlined in [TER] for performing traffic
engineering and provide a solid foundation for performing more
general constrain-based routing.

2. Build on already specified functionality that meets the
requirements whenever possible. Hence, this specifications is
based on [LDP] and the Explicit Route object and procedures
defined in [ER]. ........................................ 5
2.5 Resource Class ....................................... 5
3. Keep the solution simple Solution Overview .................................... 5
3.1 Required Messages and tractable.

In this document, support for unidirectional point-to-point CRLSPs is
specified. Support for point-to-multipoint, multipoint-to-point, is
for further study (FFS).

Support for explicitly routed LSPs in this specification depends on
the following minimal LDP behaviors as specified in [LDP]:

- Basic and/or Extended Discovery Mechanisms.

- Use the TLVs ........................... 7
3.2 Label Request Message defined in [LDP] in downstream on
demand label advertisement mode with ordered control.

- Use the ................................ 7
3.3 Label Mapping Message defined in [LDP] in downstream on
demand mode with ordered control.

- Use the ................................ 8
3.4 Notification Message defined in [LDP].

- Use the Withdraw and ................................. 9
3.5 Release & Withdraw Messages defined in [LDP].

- Loop detection (in the case of loosely routed segments of a
CRLSP) mechanisms.

In addition, the following functionality is added to what's defined
in [LDP]:

- The Label Request Message used to setup a CRLSP includes a CR- .......................... 9
4. Protocol Specification .............................. 9
4.1 Explicit Route TLV based on the path vector defined in [ER] and specified in
Section 4 of this document.

CR-LDP Specification - 4 - Exp. Apr 1999

- An LSR implicitly infers ordered control from the existence of a
CR-TLV in the (ER-TLV) ......................... 10
4.2 Explicit Route Hop TLV .............................. 10
4.3 Traffic Parameters TLV .............................. 12
4.3.1 Semantics ........................................... 13
4.3.1.1 Frequency ........................................... 13
4.3.1.2 Peak Rate ........................................... 14
4.3.1.3 Committed Rate ...................................... 14
4.3.1.4 Excess Burst Size .................................... 14
4.3.1.5 Peak Rate Token Bucket................................ 14
4.3.1.6 Committed Data Rate Token Bucket ..................... 15
4.3.1.7 Weight ......................... ..................... 16
4.3.2 Procedures ........................................... 16
4.3.2.1 Label Request Message. This means that the LSR can
still be configured for independent control for LSPs established
as a result of dynamic routing. However, when a Message ................................ 16
4.3.2.2 Label Request Mapping Message includes a CR TLV, then ordered control is used to setup
the CRLSP. Note that this is also true for ................................ 16
4.3.2.3 Notification Message ................................. 17
4.4 Preemption TLV ....................................... 18
4.5 LSPID TLV ........................................... 18
4.6 Resource Class TLV .................................. 19
4.7 ER-Hop Semantics ..................................... 19
4.7.1 ER-Hop 1 TLV IPv4 Prefix ............................. 20
4.7.2 ER-Hop 2 TLV IPv6 Prefix ............................. 20
4.7.3 ER-Hop 3 TLV AS Number ............................... 21
4.7.4 ER-Hop 4 TLV LSPID ................................... 21
4.8 Processing of the loosely routed
parts ER-TLV ............................. 22
4.8.1 Selection of a CRLSP.

- Traffic Parameters TLVs may optionally be carried in the next hop ............................ 22
4.8.2 Adding the Label Request Message to specify the CRLSP traffic characteristics. next hop ..... 24
4.9 Route Pinning TLV ................................... 24
4.10 CR-LSP FEC Element ................................... 24
4.11 Error Subcodes ...................................... 25

CR-LDP Specification - New status codes are defined to handle error notification for
failure of established paths specified in the CR-TLV.

Examples of CRLSP establishment are given in 3 - Exp. August 1999

5. Security Considerations .............................. 26
6. Acknowledgement ...................................... 26
7. References ........................................... 26
8. Author Information ................................... 28

Appendix A to illustrate
how the mechanisms described in this draft work.

3. Required Messages and TLVs

Any Messages, TLVs, CRLSP Establishment Examples ......................... 30
A.1 Strict Explicit Route Example ........................ 30
A.2 Node Groups and procedures not defined explicitly in this
document are defined in the [LDP] Specification. Specific Nodes Example ............... 31

Appendix B QoS Service Examples ................................. 34
B.1 Service Examples ..................................... 34
B.2 Establishing CR-LSP Supporting Real-Time Applications. 35
B.3 Establishing CR-LSP Delay Insensitive Applications ... 36

1. Introduction

The following
subsections are meant as a cross reference to the [LDP] document and
indication of additional functionality beyond what's defined need for constraint-based routing (CR) in [LDP]
where necessary.

3.1 Label Request Message

The Label Request Message MPLS has been explored
elsewhere [ARCH], [FRAME], and [TER]. Explicit routing is as defined in 3.5.8 a subset
of [LDP] with the
following modifications (required only if the CR-TLV is included in the Label Request Message):

- Only a single FEC-TLV may be included in more general constraint-based routing function. At the Label Request
Message.

- The Optional Parameters TLV includes MPLS WG
meeting held during the definition Washington IETF there was consensus that LDP
should support explicit routing of LSPs with provision for indication
of associated (forwarding) priority. In the
Constraint-based TLV specified Chicago meeting, a
decision was made that support for explicit path setup in Section 4 LDP will be
moved to a separate document. This document provides that support and the Traffic
Parameters TLV specified
it has been accepted as a working document in Section 5.

- The Procedures to handle the Label Request are augmented Orlando meeting.
This specification proposes an end-to-end setup mechanism of a
constraint-based routed LSP (CRLSP) initiated by the
procedures ingress LSR. We
also specify mechanisms to provide means for processing reservation of the CR-TLV as defined in Section 4.

- The Procedures to handle Service Classes are resources
using LDP.

This document introduce TLVs and procedures that provide support for:

- Strict and Loose Explicit Routing
- Specification of Traffic Parameters
- Route Pinning
- CRLSP Pre-emption though setup/holding priorities
- Handling Failures
- LSPID
- Resource Class

Section 2 introduces the various constraints defined in this
specification. Section
5.

3.2 Label Mapping Message

The Label Mapping Message 3 outlines the CR-LDP solution. Section 4
defines the TLVs and procedures used to setup constraint-based routed
label switched paths. Appendix A provides several examples of CR-LSP
path setup. Appendix B provides Service Definition Examples.

2. Constraint-based Routing Overview

Constraint-based routing is as a mechanism that supports the Traffic
Engineering requirements defined in 3.5.7 [TER]. Explicit Routing is a
subset of [LDP] with the
following modifications:

- Only a single Label-TLV may be included in more general constraint-based routing where the Label Mapping
Message.

CR-LDP Specification - 5 4 - Exp. Apr August 1999

- The FEC-Label Mapping TLV does not include any of

constraint is the optional
TLVs.

- The Label Mapping Message Procedures explicit route (ER). Other constraints are limited defined
to downstream
on demand ordered provide a network operator with control mode of mapping.

A Mapping message is transmitted over the path taken by a downstream LSR to an upstream
LSR under one of the following conditions:

1. The LSR
LSP. This section is the egress end an overview of the CRLSP various constraints supported
by this specification.

2.1 Strict and an upstream mapping
has been requested.

2. The LSR received a mapping from its downstream next hop LSR for Loose Explicit Routes

Like any other LSP an CRLSP for which an upstream request is still pending.

3.3. Notification Message a path through an MPLS network. The Notification message
difference is as defined in Section 3.5.1 of [LDP] and
the Status TLV encoding is as defined in Section 3.4.7 of [LDP].

Establishment of an Explicitly Routed LSP may fail for a variety of
reasons. All such failures are considered advisory conditions and
they are signaled by the Notification Message.

Notification messages carry Status TLVs to specify events being
signaled. New status codes that while other paths are defined setup solely based on
information in Section 4.8.3 to signal
error notifications associated with the establishment of routing tables or from a CRLSP and
the processing of management system, the CR-TLV.

4. Constraint-based Routing TLV

Label Request Messages defined in [LDP] optionally carry
constraint-based route is calculated at one point at the
Constraint-based Routing TLV (CR-TLV) edge of
network based on criteria, including but not limited to routing
information. The intention is that this functionality shall give
desired special characteristics to the path vector
defined in [ER] and described LSP in this section of order to better support
the specification. traffic sent over the LSP. The inclusion of reason for setting up CRLSPs,
might be that one wants to assign certain bandwidth or other Service
Class characteristics to the CR TLV in LSP, or that one wants to make sure that
alternative routes use physically separate paths through the network.

An explicit route is represented in a Label Request Message indicates as a
list of nodes or groups of nodes along the path to be taken in constraint-based route.
When the network even if normal routing indicates
otherwise.

The format CRLSP is established, all or a subset of the CR-TLV is described below.

4.1 CR-TLV

The CR-TLV is an object that specifies nodes in a
group may be traversed by the path LSP. Certain operations to be taken by
performed along the
LSP being established. In addition, the CR-TLV may path can also include be encoded in the constraint-based
route.

The capability to specify, in addition to specified nodes, groups of
nodes, of which a subset will be traversed by the Service Class (SC) constraints associated with CRLSP, allows the LSP,
system a setup
and significant amount of local flexibility in fulfilling a holding priority used
request for a constraint-based route. This allows the generator of
the constraint-based route to have some degree of imperfect
information about the details of the path.

The constraint-based route is encoded as a series of ER-Hops
contained in a constraint-based route TLV. Each ER-Hop may identify
a group of nodes in the constraint-based route. A constraint-based
route is then a path bumping, and including all of the identified groups of nodes.

To simplify the discussion, we call each group of nodes an LSP pinning
request flag. Reserved bits in abstract
node. Thus, we can also say that a constraint-based route is a path
including all of the CR-TLV allow for abstract nodes, with the
specification specified operations
occurring along that path.

2.2 Traffic Characteristics

The traffic characteristics of other LSP attributes a path are described in the future. If Traffic
Parameters TLV in terms of a peak rate, committed rate, and service
granularity. The peak and committed rates describe the reserved
bits are exhausted, additional TLVs may bandwidth
constraints of a path while the service granularity can be specified used to allow for
specify a constraint on the
indication of other LSP attributes during delay variation that the CRLSP setup. CRLDP MPLS
domain may introduce to a path's traffic.

CR-LDP Specification - 6 5 - Exp. Apr August 1999

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| CR-TLV (0x0800) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Reserved | SC |P| Hp | Sp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ER-Hop TLV 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ER-Hop TLV 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ............ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ER-Hop TLV n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit

Unknown TLV bit. Upon receipt

2.3 Pre-emption

CR-LDP signals the resources required by a path on each hop of an unknown TLV, if clear (=0), the
route. If a
notification must route with sufficient resources can not be returned to the message originator and the
entire message must found,
existing paths may be ignored; if set (=1), rerouted to reallocate resources to the unknown TLV new
path. This is
silently ignored and the rest process of the message is processed as if the
unknown TLV did not exist.

F bit

Forward unknown TLV bit. This bit only applies when the U bit is set path pre-emption. Setup and the LDP message containing the unknown TLV is holding
priorities are used to be forwarded.
If clear (=0), the unknown TLV is not forwarded with rank existing paths (holding priority) and the containing
message;
new path (setup priority) to determine if set (=1), the unknown TLV is forwarded with the
containing message.

Type

A two byte field carrying new path can pre-empt
an existing path.

The setupPriority of a new CRLSP and the value holdingPriority attributes
of the CR-TLV type which is
0x800.

Length

Specifies existing CRLSP are used to specify priorities. Signaling a
higher holding priority expresses that the length path, once it has been
established, should have a lower chance of being pre-empted.
Signaling a higher setup priority expresses the value field expectation that, in bytes.

Reserved

This field
the case that resource are unavailable, the path is reserved. It must be set to zero on transmission and
must be ignored on receipt. We expect more likely to use these fields for
carrying information that support
pre-empt other constrain-based routing
information.

P bit

CR-LDP Specification - 7 - Exp. Apr 1999

When set indicates that the loosely routed segments must remain
pinned-down. CRLSP must be rerouted only when adjacency is lost
along the segment. When not set, it indicates that the loose segment
is not pinned down and must be changed to match the underlying hop-
by-hop path.

SC paths. The SC Field is used to specify the Service Class exact rules determining bumping are an
aspect of the CRLSP. This
field allows for the definition network policy.

The allocation of up to 8 different Service Classes.
Currently, Three Service Classes are defined: Best Effort (0),
Throughput Sensitive (1), setup and Delay Sensitive (2) Service Classes.
These SCs are further defined in Section 5.

A SetupPriority of value zero (0) is the holding priority assigned to the
most important path. It is referred values to as the highest priority. Four
(4) paths is the priority for the least important path. an
aspect of network policy.

The higher the setup priority, the more paths CR-LDP can bump and holding priority values range from zero (0) to set up the path. seven
(7). The default value is 2. Values 5, 6, and 7 are reserved.

A HoldingPriority of value zero (0) is the priority assigned to the most
important path. It is referred to as the highest priority. Four
(4) Seven (7)
is the priority for the least important path. The higher the
holding priority, the less likely it is for CR-LDP to reallocate its
bandwidth to a new path. The use of default value
priority values is 2. Values 5, 6, and 7
are reserved.

4.1.1 Setup and holding priorities

CR-LDP signals the resources required by a path on each hop an aspect of network policy.

The setupPriority of the
route. If a route with sufficient resources can CRLSP should not be found,
existing paths may higher (numerically less)
than its holdingPriority since it might bump an LSP and be rerouted to reallocate resources to the new
path. This bumped by
next "equivalent" request.

2.4 Route Pinning

Route pinning is the process of bumping paths. Setup and holding
priorities are used to rank existing paths (holding priority) and the
new path (setup priority) applicable to determine if the new path can bump an
existing path.

The setupPriority segments of an LSP that are loosely
routed - i.e. those segments which are specified with a new CRLSP and next hop with
the holdingPriority attributes
of 'L' bit set or where the existing next hop is an "abstract node". A CRLSP are used to specify these priorities. The
higher the holding priority, the less likely
may be setup using route pinning if it is for CR-LDP to
reallocate its bandwidth undesirable to a new path. Similarly, the higher the
setup priority, change the more paths CR-LDP can bump to set up
path used by an LSP because a better next hop becomes available at
some LSR along the path.

The setup and holding priority values range from zero (0) to four
(4). The value zero (0) is loosely routed portion of the priority assigned to LSP.

2.5 Resource Class

Network resources may be classified in various ways by the most
important path. It network
operator. These classes are also known as "colors" or "administrative
groups". When an CR-LSP is referred being established, it's necessary to as
indicate which resource classes the highest priority. Four (4) CR-LSP can draw from.

3. Solution Overview

CRLSP over LDP Specification is designed with the priority for the least important path. The default values for following goals:

CR-LDP Specification - 8 6 - Exp. Apr August 1999

both setup and holding priority should be 2. By setting

1. Meet the default
value of both setup requirements outlined in [TER] for performing traffic
engineering and holding priorities at the middle of the
range, all connections are initially treated the same. However, when
network operators see provide a need solid foundation for performing more
general constraint-based routing.

2. Build on already specified functionality that meets the use of path bumping, the values
of setup
requirements whenever possible. Hence, this specifications is
based on [LDP] and holding priorities can be gracefully adjusted up or down
from the middle of the range.

An existing path can be bumped if Explicit Route object and only if the setupPriority of procedures
defined in [ER].

3. Keep the new path solution simple.

In this document, support for unidirectional point-to-point CRLSPs is numerically less than
specified. Support for point-to-multipoint, multipoint-to-point, is
for further study (FFS).

Support for constraint-based routed LSPs in this specification
depends on the holdingPriority of following minimal LDP behaviors as specified in [LDP]:

- Basic and/or Extended Discovery Mechanisms.

- Use the
existing path.

To illustrate Label Request Message defined in [LDP] in downstream on
demand label advertisement mode with ordered control.

- Use the use of Label Mapping Message defined in [LDP] in downstream on
demand mode with ordered control.

- Use the setup and holding priority, consider a
network which supports two service types (e.g., video and data
services). The video traffic is given a low setup priority because
new video paths can use an alternate public network if Notification Message defined in [LDP].

- Use the primary
network cannot accommodate Withdraw and Release Messages defined in [LDP].

- Use the new path. However, Loop Detection (in the video traffic
is given case of loosely routed segments
of a high holding priority since it is undesirable for CRLSP) mechanisms defined in [LDP].

In addition, the path following functionality is added to be rerouted during an active LSP. For data traffic, high setup and
holding priorities are desirable since data paths cannot be
established on an alternate network. what's defined
in [LDP]:

- The setup and holding priorities can be different Label Request Message used to allow setup at a CRLSP includes one priority and holding at an independent priority. This would allow
some calls not to invoke bumping and not to be bumped at or
more CR-TLVs defined in Section 4. For instance, the same
time.

The setupPriority Label Request
Message may include the ER-TLV.

- An LSR implicitly infers ordered control from the existence of a CRLSP should not be higher (numerically less)
than its holdingPriority since it might bump an LSP and
one or more CR-TLVs in the Label Request Message. This means that
the LSR can still be bumped by
next "equivalent" request.

Bumping by default only happens as a last resort when there are no
routes available configured for independent control for LSPs
established as a given path.

During the instantiation result of dynamic routing. However, when a path that must bump other paths, lower
holding priority paths are bumped before higher priority paths. The
decision as to which Label
Request Message includes one or more of the available paths are bumped at each
intermediate node by CR-TLVs, then ordered
control is used to setup the new path CRLSP. Note that this is arbitrary.

4.2 ER-Hop TLV

The contents also true
for the loosely routed parts of a constraint-based route TLV CRLSP.

- New status codes are a series defined to handle error notification for
failure of variable
length ER-Hop TLVs. Each ER-Hop TLV has established paths specified in the form:

0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--------//--------------+
|L| Type | Length | Contents |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--------//--------------+

L CR-TLV.

CR-LDP Specification - 9 7 - Exp. Apr August 1999

The L bit is an attribute

Examples of the ER-Hop. The L bit is set if the
ER-Hop represents a loose hop CRLSP establishment are given in Appendix A to illustrate
how the explicit route. If the bit is mechanisms described in this draft work.

3.1 Required Messages and TLVs

Any Messages, TLVs, and procedures not set, the ER-Hop represents a strict hop defined explicitly in this
document are defined in the explicit route.

Type

A seven-bit field indicating [LDP] Specification. The state
transitions which relate to CR-LDP messages can be found in [LDP-
STATE].

The following subsections are meant as a cross reference to the type of contents [LDP]
document and indication of the ER-Hop.
Currently additional functionality beyond what's
defined values are:

Value Type
----- ------------------------
0 Reserved
1 IPv4 prefix
2 IPv6 prefix
32 Autonomous system number

Length in [LDP] where necessary.

3.2 Label Request Message

The Length field contains Label Request Message is as defined in 3.5.8 of [LDP] with the total length
following modifications (required only if any of the ER-Hop CR-TLVs is
included in bytes. It
includes the L bit, Type and Length fields. The length must always be Label Request Message):

- Only a multiple of 4, and at least 4.

Contents

A variable length field containing single FEC-TLV may be included in the node or abstract node that Label Request
Message. The CR-LSP FEC TLV should be used.

- The Return Message ID TLV is MANDATORY.

- The Optional Parameters TLV includes the consecutive nodes that make up definition of any of
the explicit routed LSP.

4.3 Applicability

The CR-TLV Constraint-based TLVs specified in this version of Section 4.

- The Procedures to handle the specification is intended for
unicast only. CRLSPs for multicast Label Request Message are FFS.

4.4 Semantics of augmented
by the CR-TLV

Like any other LSP an CRLSP is a path through a network. The
difference is that while other paths are setup solely based on
information in routing tables or from a management system, the
constraint-based route is calculated at one point at the edge procedures for processing of
network based on criteria, including but not limited to routing
information. The intention is that this functionality shall give
desired special characteristics to the LSP CR-TLVs as defined in order to better support
the traffic sent over the LSP.
Section 4.

The reason encoding for setting up CRLSPs,
might be that one wants to assign certain bandwidth or other Service
Class characteristics to the LSP, or that one wants to make sure that
alternative routes use physically separate paths through the network.

A CRLSP is represented in a CR-LDP Label Request Message as a list of nodes
or groups of nodes along the constraint-based route. When the CRLSP is established, all or a subset of the nodes in a group may be as follows:

CR-LDP Specification - 10 8 - Exp. Apr August 1999

traversed by the LSP. Certain operations to be performed along the
path can also be encoded in the constraint-based route.

The capability to specify, in addition to specified nodes, groups of
nodes, of which a subset will be traversed by the CRLSP, allows the
system a significant amount of local flexibility in fulfilling a
request for a constraint-based route. This allows the generator of
the constraint-based route to have some degree of imperfect
information about the details of the path.

The constraint-based route is encoded as a series of ER-Hops
contained in

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| Label Request (0x0401) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FEC TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Message ID TLV (mandatory) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSPID TLV (CR-LDP, mandatory) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ER-TLV (CR-LDP, optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic TLV (CR-LDP, optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pinning TLV (CR-LDP, optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Resource Class TLV (CR-LDP, optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pre-emption TLV (CR-LDP, optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.3 Label Mapping Message

The Label Mapping Message is as defined in 3.5.7 of [LDP] with the
following modifications:

- Only a constraint-based route TLV. Each ER-Hop single Label-TLV may identify
a group of nodes be included in the constraint-based route. Label Mapping
Message.

- The Label Mapping Message MUST include Label Request Message ID
TLV.

- The Label Mapping Message MUST include LSPID TLV.

- The Label Mapping Message Procedures are limited to downstream
on demand ordered control mode.

A constraint-based
route Mapping message is then transmitted by a path including all of the identified groups of nodes.

To simplify the discussion, we call each group of nodes downstream LSR to an abstract
node. Thus, we can also say that a constraint-based route is a path
including all upstream
LSR under one of the abstract nodes, with the specified operations
occurring along that path.

4.5 Strict and Loose ER-Hops following conditions:

1. The L bit in the ER-Hop is a one-bit attribute. If the L bit is set,
then the value of the attribute LSR is "loose." Otherwise, the value egress end of the attribute is "strict." For brevity, we say that if the value of
the ER-Hop attribute is loose then it is a "loose ER-Hop."
Otherwise, it's a "strict ER-Hop." Further, we say that the abstract
node of a strict or loose ER-Hop is a strict or a loose node,
respectively. Loose CRLSP and strict nodes are always interpreted relative
to their prior abstract nodes. an upstream mapping
has been requested.

2. The path between LSR received a strict node and its prior node MUST include only
network nodes mapping from the strict node and its prior abstract node.

The path between a loose node and its prior node MAY include other
network nodes downstream next hop LSR for
an CRLSP for which are not part of the strict node or its prior
abstract node.

4.6 Loops

While the constraint-based route TLV an upstream request is of finite length, still pending.

The encoding for the
existence of loose nodes implies that it CR-LDP Label Mapping Message is possible to construct
forwarding loops during transients in the underlying routing
protocol. This may be detected by the originator of the constraint-
based route through the use a path vector object as defined in [LDP].

4.7 ER-Hop semantics

4.7.1. ER-Hop 1: The IPv4 prefix

The contents of an IPv4 prefix ER-Hop are a 4 byte IPv4 address, 1 follows:

CR-LDP Specification - 11 9 - Exp. Apr August 1999

byte of prefix length, and 1 byte of padding. The abstract node
represented by this ER-Hop is the set of nodes which have an IP
address which lies within this prefix. Note that a prefix length of
32 indicates a single IPv4 node.

The length of the IPv4 prefix ER-Hop is 8 bytes. The contents of the
1 byte of padding must be zero on transmission and must not be
checked on receipt.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type
|U| Label Mapping (0x0400) | Message Length | IPv4 Address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address (Continued) Message ID | Prefix |0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type

IPv4 Address 0x01

Length

A one byte field indicating the total length of the TLV in bytes. It
includes the L-bit, the Type, Length, the IP Address, and the Prefix
fields. The length is always 8 bytes.

IP Address

A four byte field indicating the IP Address.

Prefix Length

1-32

Padding

Zero on transmission. Ignored on receipt.

4.7.2. ER-Hop 2: The IPv6 address

CR-LDP Specification - 12 - Exp. Apr 1999

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type
| Length | IPV6 address (16 bytes) FEC TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV6 address (continued) Label TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV6 address (continued) Label Request Message ID TLV (mandatory) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV6 address (continued) LSPID TLV (CR-LDP, mandatory) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV6 address (continued) Traffic TLV (CR-LDP, optional) | Prefix |0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type

0x02 IPv6 address

Length

3.4 Notification Message

The Length contains the total length Notification Message is as defined in Section 3.5.1 of [LDP] and
the ER-Hop Status TLV in bytes,
including the Type and Length fields. The Length encoding is always 20.

IPv6 address

A 128-bit unicast host address.

Prefix Length

1-128

Padding

Zero on transmission. Ignored on receipt.

4.7.3. ER-Hop 32: The autonomous system number

The contents as defined in Section 3.4.7 of [LDP].

Establishment of an autonomous system (AS) number ER-Hop are Explicitly Routed LSP may fail for a 2 byte
autonomous system number. The abstract node represented variety of
reasons. All such failures are considered advisory conditions and
they are signaled by this ER-
Hop is the set Notification Message.

Notification Messages carry Status TLVs to specify events being
signaled. New status codes are defined in Section 4.11 to signal
error notifications associated with the establishment of nodes belonging a CRLSP and
the processing of the CR-TLV.

The Notification Message must carry the LSPID TLV of the
corresponding CRLSP.

3.5 Release and Withdraw Messages

The Label Release and Label Withdraw Messages are used as specified
in [LDP] to clear CR-LSPs. These message may also carry the autonomous system. LSPID
TLV.

4. Protocol Specification

The length Label Request Messages defined in [LDP] optionally carries one or
more of the AS number ER-Hop optional Constraint-based Routing TLVs (CR-TLVs) defined
in this section. If needed, other constraints can be supported later
through the definition of new TLVs. In this specification, the
following TLVs are defined:

- Explicit Route TLV

CR-LDP Specification - 10 - Exp. August 1999

- Explicit Route Hop TLV
- Traffic Parameters TLV
- Preemption TLV
- LSPID TLV
- Route Pinning TLV
- Resource Class TLV
- CRLSP FEC TLV

4.1 Explicit Route TLV (ER-TLV)

The ER-TLV is 4 bytes. an object that specifies the path to be taken by the
LSP being established. It is composed of one or more Explicit Route
Hop TLVs (ER-Hop TLVs) defined in Section 4.2.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type
|U|F| ER-TLV (0x0800) | Length | Autonomous System number
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ER-Hop TLV 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type

CR-LDP Specification - 13 - Exp. Apr 1999

AS Number 0x20

Length

A one byte field indicating the total length of the
| ER-Hop TLV in bytes. It
includes the L-bit, the Type, and Length, and the AS number fields.
The length is always 4 bytes.

AS number 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ............ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ER-Hop TLV n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

Type
A two byte field indicating carrying the AS number.

4.8. Processing value of the Constraint-Based ER-TLV type which
is 0x800.

Length
Specifies the length of the value field in bytes.

ER-Hop TLVs
One or more ER-Hop TLVs defined in Section 4.2.

4.2 Explicit Route Hop TLV

4.8.1. Selection (ER-Hop TLV)

The contents of the next hop

A Label Request message containing an ER-TLV are a constraint-based route series of variable length ER-Hop
TLVs. Each ER-Hop TLV must
determine has the next hop for this path. Selection form:

CR-LDP Specification - 11 - Exp. August 1999

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| ER-Hop-Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Content // |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

ER-Hop Type
A fourteen-bit field indicating the type of this next hop may
involve a selection from a set contents of possible alternatives.
the ER-Hop. Currently defined values are:

Value Type
----- ------------------------
0x801 IPv4 prefix
0x802 IPv6 prefix
0x803 Autonomous system number
0x804 LSPID

Length
Specifies the length of the value field in bytes.

L bit
The
mechanism for making a selection from this set is implementation
dependent and L bit is outside an attribute of the scope of this specification.
Selection of particular paths ER-Hop. The L bit is also outside of set if the scope of this
specification, but it is assumed that each node will make a best
effort attempt to determine
ER-Hop represents a loop-free path. Note that such best
efforts may be overridden by local policy.

To determine the next loose hop for the path, a node performs the following
steps:

1) The node receiving the Label Request message must first
evaluate in the first ER-Hop. explicit route. If the L bit is
not set in set, the first ER-Hop and if the node is not part of the abstract node described
by the first ER-Hop, it has received represents a strict hop in the message explicit route.

The L bit in error, and
should return the ER-Hop is a "Bad initial ER-Hop" error. one-bit attribute. If the L bit is set
and
set, then the local node is not part value of the abstract node described by attribute is "loose." Otherwise, the first ER-Hop,
value of the node selects a next hop that attribute is along the
path to "strict." For brevity, we say that if
the abstract node described by value of the first ER-Hop. If there ER-Hop attribute is no first ER-Hop, the message loose then it is also in error and the system
should return a "Bad Constraint-Based Routing TLV" error.

2) If there is no second ER-Hop, this indicates the end of the
constraint-based route. The constraint-based route TLV should be
removed from "loose
ER-Hop." Otherwise, it's a "strict ER-Hop." Further, we say that
the Label Request message. This abstract node may or may not
be the end of the LSP. Processing continues with section 4.8.2,
where a new constraint-based route TLV may be added to the Label
Request message.

3) If the node strict or loose ER-Hop is also a part of the strict or a
loose node, respectively. Loose and strict nodes are always
interpreted relative to their prior abstract nodes.

The path between a strict node described by
the second ER-Hop, then the and its prior node deletes MUST include
only network nodes from the first ER-Hop strict node and
continues processing with step 2, above. Note that this makes the
second ER-Hop into the first ER-Hop its prior abstract
node.

The path between a loose node and its prior node MAY include other
network nodes which are not part of the next iteration. strict node or its prior
abstract node.

CR-LDP Specification - 14 12 - Exp. Apr August 1999

4) The node determines if it is topologically adjacent to the
abstract node described by the second ER-Hop. If so,

Contents
A variable length field containing the node
selects a particular next hop which is a member of the or abstract
node. The node then deletes that
is the first ER-Hop and continues
processing with section 4.8.2.

5) Next, consecutive nodes that make up the node selects a next hop within explicit routed LSP.

4.3 Traffic Parameters TLV

The following sections describe the abstract node CRLSP Traffic Parameters. The
required characteristics of a CRLSP are expressed by the first ER-Hop that Traffic
Parameter values.

A Traffic Parameters TLV, is along the path used to signal the abstract node of
the second ER-Hop. If no such path exists then there Traffic Parameter
values. The Traffic Parameters are two
cases:

5a) If defined in the second ER-Hop is subsequent
sections.

The Traffic Parameters TLV contains a strict ER-Hop, then there is an
error and the node should return Flags field, a "Bad strict node" error.

5b) Otherwise, if the second ER-Hop is Frequency, a loose ER-Hop, then
Weight, and the
node selects any next hop that five Traffic Parameters PDR, PBS, CDR, CBS, EBS. The
Traffic Parameters TLV is along shown 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Traf. Param. TLV (0x0810)| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Frequency | Reserved | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peak Data Rate (PDR) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peak Burst Size (PBS) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Committed Data Rate (CDR) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Committed Burst Size (CBS) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Excess Burst Size (EBS) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

Type
A fourteen-bit field carrying the path to value of the next
abstract node. If no path exists, then there ER-TLV type which
is an error, and the
node should return a "Bad loose node" error.

6) Finally, the node replaces the first ER-Hop with any ER-Hop
that denotes an abstract node containing 0x810.

Length
Specifies the next hop. This is
necessary so that when length of the constraint-based route value field in bytes.

Flags
The Flags field is received by shown below:

CR-LDP Specification - 13 - Exp. August 1999

+--+--+--+--+--+--+--+--+
| Res |F6|F5|F4|F3|F2|F1|
+--+--+--+--+--+--+--+--+

Res - These bits are reserved.
Zero on transmission.
Ignored on receipt.
F1 - Corresponds to the next hop, it will be accepted.

7) Progress PDR.
F2 - Corresponds to the Label Request Message PBS.
F3 - Corresponds to the next hop.

4.8.2. Adding ER-Hops CDR.
F4 - Corresponds to the constraint-based route TLV

After selecting a next hop, CBS.
F5 - Corresponds to the node may alter EBS.
F6 - Corresponds to the constraint-based
route in the following ways.

If, as part of executing the algorithm in section 4.8.1, the
constraint-based route TLV Weight.

Each flag Fi is removed, the node may add a new
constraint-based route TLV.

Otherwise, if the node is Negotiable Flag corresponding to a member of Traffic
Parameter. The Negotiable Flag value zero denotes NotNegotiable
and value one denotes Negotiable.

Frequency
The Frequency field is coded as an 8 bit unsigned integer with
the abstract node for following code points defined:

0 - Unspecified
1 - Frequent
2 - VeryFrequest
3-255 - Reserved

Reserved
Zero on transmission. Ignored on receipt.

Weight
An 8 bit unsigned integer indicating the first
ER-Hop, then a series weight of ER-Hops may be inserted before the first
ER-Hop or may replace CRLSP.
Valid weight values are from 1 to 255. The value 0 means
that weight is not applicable for the first ER-Hop. CRLSP.

Traffic Parameters
Each ER-Hop in this series
must denote an abstract node that Traffic Parameter is encoded as a subset 32 bit IEEE single-
precision floating point number. A value of the current abstract
node.

Alternately, if the first ER-Hop positive infinity is a loose ER-Hop,
represented as an arbitrary
series IEEE single-precision floating-point number with
an exponent of ER-Hops may all ones (255) and a sign and mantissa of all
zeros. The values PDR and CDR are in units of bytes per second.
The values PBS, CBS and EBS are in units of bytes.

The value of PDR MUST be inserted prior greater than or equal to the first ER-Hop.

4.8.3. Error subcodes

In the processing described above, certain errors need to be reported
as part value of the Notification message. This section defines the status
codes for the errors described above. CDR
in a correctly encoded Traffic Parameters TLV.

4.3.1 Semantics

4.3.1.1 Frequency

CR-LDP Specification - 15 14 - Exp. Apr August 1999

Status Code Type
-------------------------------------- ----------
Bad Constraint-Based Routing TLV Error 0x04000001
Bad Strict Node Error 0x04000002
Bad Loose Node Error 0x04000003
Bad Initial ER-Hop Error 0x04000004
Resource Unavailable 0x04000005
Service Class Unavailable 0x04000006
Traffic Parameters Unavailable 0x04000007

5.0 CRLSP Service Classes and Traffic Parameters

The following sections describe Frequency specifies at what granularity the CDR allocated to the
CRLSP Service Classes (SCs), and
their associated traffic parameters.

The CRLSP Service Class is signaled in made available. The value VeryFrequently means that the SC Field of
available rate should average at least the CR-TLV
defined in Section 4.1.

Three Service Classes are currently supported by CR-LDP:

Service Class Value
-------------------------- -----
Best Effort (BE) 0x0
Throughput Sensitive (TS) 0x1
Delay Sensitive (DS) 0x2

These service classes are specified in CDR when measured over any
time interval equal to or longer than the following sections.

5.1 Best Effort (BE) shortest packet time at the
CDR. The request value Frequently means that the available rate should
average at least the CDR when measured over any time interval equal
to or longer than a small number of shortest packet times at the BE SC implies CDR.
The value Unspecified means that there are no expected service
guarantees from the network. The service CDR MAY be provided by at any
granularity.

4.3.1.2 Peak Rate

The Peak Rate defines the network is maximum rate at which traffic SHOULD be
sent to the familiar best effort service. CRLSP. The Peak Date Rate (PDR) is useful for the only traffic parameter that may purpose of
resource allocation. If resource allocation within the MPLS domain
depends on the Peak Rate value then it should be
specified with enforced at the BE SC.
ingress to the MPLS domain.

The specification Peak Rate is defined in terms of the two Traffic Parameters PDR allows the
network to perform traffic shaping
and policing functions.

5.2 Throughput Sensitive (TS)

In the service model for PBS, see section 4.3.1.5 below.

4.3.1.3 Committed Rate

The Committed Rate defines the Throughput Sensitive SC, rate that the network MPLS domain commits to deliver with high probability user datagrams at a rate
be available to the CRLSP.

The Committed Rate is defined in terms of
at least the two Traffic Parameters
CDR (Committed Data Rate). and CBS, see section 4.3.1.6 below.

4.3.1.4 Excess Burst Size

The user Excess Burst Size may transmit be used at a rate
higher than CDR but datagrams the edge of an MPLS domain for
the purpose of traffic conditioning. The EBS MAY be used to measure
the extent by which the traffic sent on a CRLSP exceeds the committed
rate.

The possible traffic conditioning actions, such as passing, marking
or dropping, are specific to the MPLS domain.

The Excess Burst Size is defined together with the Committed Rate,
see section 4.3.1.6 below.

4.3.1.5 Peak Rate Token Bucket

The Peak Rate of a CRLSP is specified in terms of a token bucket P
with token rate PDR and maximum token bucket size PBS.

The token bucket P is initially (at time 0) full, i.e., the token
count Tp(0) = PBS. Thereafter, the token count Tp, if less than PBS,
is incremented by one PDR times per second. When a packet of size B
bytes arrives at time t, the following happens:

CR-LDP Specification - 15 - Exp. August 1999

o If Tp(t)-B >= 0, the packet is not in excess of CDR would have the peak
rate and Tp is decremented by B down to the minimum value
of 0, else

o the packet is in excess of the peak rate and Tp is
not decremented.

Note that according to the above definition, a lower
probability positive infinite
value of being delivered. either PDR or PBS implies that arriving packets are never in
excess of the peak rate.

The actual implementation of a LSR doesn't need to be modeled
according to the above formal token bucket specification.

4.3.1.6 Committed Data Rate Token Bucket

The committed rate of a CRLSP is specified in terms of a token bucket
C with rate CDR. The extent by which the offered rate exceeds the
committed rate MAY be measured in terms of another token bucket E,
which also operates at rate CDR. The maximum size of the token
bucket C is CBS and the maximum size of the token bucket E is EBS.

The token buckets C and E are initially (at time 0) full, i.e., the
token count Tc(0) = CBS and the token count Te(0) = EBS. Thereafter,
the token counts Tc and Te are updated CDR times per second as
follows:

o If Tc is less than CBS, Tc is incremented by one, else

o if Te is less then EBS, Te is incremented by one, else

o neither Tc nor Te is incremented.

When a packet of size B bytes arrives at time t, the following
happens:

o If Tc(t)-B >= 0, the packet is not in excess of the Committed
Rate and Tc is decremented
by B down to the minimum value of 0, else

o if Te(t)-B >= 0, the packet is in excess of the Committed Rate
but is not in excess of the EBS and Te is
decremented by B down to the minimum value of 0, else

o the packet is in excess of both the Committed Rate and the EBS
and neither Tc nor Tc is decremented.

Note that according to the above specification, a CDR value of
positive infinity implies that arriving packets are never in excess
of either the Committed Rate or EBS. A positive infinite value of
either CBS or EBS implies that the respective limit cannot be

CR-LDP Specification - 16 - Exp. August 1999

exceeded.

The actual implementation of a LSR doesn't need to be modeled
according to the above formal specification.

4.3.1.7 Weight

The weight determines the CRLSP's relative share of the possible
excess bandwidth above its committed rate. The definition of
"relative share" is MPLS domain specific.

4.3.2 Procedures

4.3.2.1 Label Request Message

If an LSR receives an incorrectly encoded Traffic Parameters TLV in
which the value of PDR is less than the value of CDR then it MUST
send a Notification Message including the Status code Traffic
Parameters Unavailable to the upstream LSR from which it received the
erroneous message.

If a Traffic Parameter is indicated as Negotiable in the Label
Request Message by the corresponding Negotiable Flag then an LSR MAY
replace the Traffic Parameter value with a smaller value.

If the Weight is indicated as Negotiable in the Label Request Message
by the corresponding Negotiable Flag then an LSR may adjust replace
the Weight value with a lower value (down to 1).

If, after possible Traffic Parameter negotiation, an LSR can support
the CRLSP Traffic Parameters then the LSR MUST reserve the
corresponding resources for the CRLSP.

If, after possible Traffic Parameter negotiation, an LSR cannot
support the CRLSP Traffic Parameters then the LSR MUST send a
notification message that contains the Resource Unavailable status
code.

4.3.2.2 Label Mapping Message

If an LSR receives an incorrectly encoded Traffic Parameters TLV in
which the value of PDR is less than the value of CDR then it MUST
send a Label Release message containing the Status code Traffic
Parameters Unavailable to the LSR from which it received the
erroneous message.

The egress LSR MUST include the (possibly negotiated) Traffic
Parameters and Weight in the Label Mapping message.

The Traffic Parameters and the Weight in a Label Mapping message MUST
be forwarded unchanged.

CR-LDP Specification - 17 - Exp. August 1999

An LSR SHOULD adjust the resources that it reserved for a CRLSP when
it receives a Label Mapping Message if the Traffic Parameters differ
from those in the corresponding Label Request Message.

4.3.2.3 Notification Message

If an LSR receives a Notification Message for a CRLSP, it SHOULD
release any resources that it possibly had reserved for the CRLSP.

In addition, on receiving a Notification Message from a Downstream
LSR that is associated with a Label Request from an upstream LSR, the
local LSR MUST propagate the Notification message using the
procedures in [LDP].

4.4 Preemption TLV

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Preemption-TLV (0x0820) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SetPrio | HoldPrio | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

Type
A fourteen-bit field carrying the value of the Preemption-TLV
type which is 0x810.

Length
Specifies the length of the value field in bytes.

Reserved
Zero on transmission. Ignored on receipt.

SetPrio
A SetupPriority of value zero (0) is the priority assigned to the
most important path. It is referred to as the highest priority.
Seven (7) is the priority for the least important path. The higher
the setup priority, the more paths CR-LDP can bump to set up the
path.

HoldPrio
A HoldingPriority of value zero (0) is the priority assigned to
the most important path. It is referred to as the highest
priority. Seven (7) is the priority for the least important path.

CR-LDP Specification - 18 - Exp. August 1999

The higher the holding priority, the less likely it is for CR-LDP
to reallocate its bandwidth to a new path.

4.5 LSPID TLV

LSPID is a unique identifier of a CRLSP within an MPLS network.

The LSPID is composed of the ingress LSR Router ID and a Locally
unique CRLSP ID to that LSR.

The LSPID is useful in network management, in CR-LSP repair, and in
using an already established CR-LSP as a hop in an ER-TLV.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| LSPID-TLV (0x0821) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Local CRLSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ingress LSR Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

Type
A fourteen-bit field carrying the value of the LSPID-TLV
type which is 0x821.

Length
Specifies the length of the value field in bytes.

Reserved
Zero on transmission. Ignored on receipt.

Local CRLSP ID
The Local LSP ID is an identifier of the CRLSP locally unique
within the Ingress LSR originating the CRLDP.

Ingress LSR Router ID
A 4 byte field indicating the Ingress LSR ID.

4.6 Resource Class (Color) TLV

The Resource Class as defined in [TER] is used to specify which links
are acceptable by this CRLSP. This information allows for the

CR-LDP Specification - 19 - Exp. August 1999

networks topology to be pruned.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| ResCls-TLV (0x0822) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RsCls |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

Type
A fourteen-bit field carrying the value of the ResCls-TLV
type which is 0x822.

Length
Specifies the length of the value field in bytes.

RsCls
The Resource Class bit mask indicating which of the
32 "administrative groups" or "colors" of links
the CRLSP can traverse.

4.7 ER-Hop semantics

4.7.1. ER-Hop 1: The IPv4 prefix

The abstract node represented by this ER-Hop is the set of nodes
which have an IP address which lies within this prefix. Note that a
prefix length of 32 indicates a single IPv4 node.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| 0x801 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Reserved | PreLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

CR-LDP Specification - 20 - Exp. August 1999

Type
IPv4 Address 0x801

Length
Specifies the length of the value field in bytes.

L Bit
Set to indicate Loose hop.
Cleared to indicate a strict hop.

Reserved
Zero on transmission. Ignored on receipt.

PreLen
Prefix Length 1-32

IP Address
A four byte field indicating the IP Address.

4.7.2. ER-Hop 2: The IPv6 address

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| 0x802 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Reserved | PreLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV6 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

Type
0x802 IPv6 address

Length
Specifies the length of the value field in bytes.

L Bit
Set to indicate Loose hop.

CR-LDP Specification - 21 - Exp. August 1999

Cleared to indicate a strict hop.

Reserved
Zero on transmission. Ignored on receipt.

PreLen
Prefix Length 1-128

IPv6 address
A 128-bit unicast host address.

4.7.3. ER-Hop 32: The autonomous system number

The abstract node represented by this ER-Hop is the set of nodes
belonging to the autonomous system.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| 0x803 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Reserved | AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

Type
AS Number 0x803

Length
Specifies the user sends at a rate length of CDR or
lower the network commits value field in bytes.

L Bit
Set to deliver with high probability all the
user datagrams. indicate Loose hop.
Cleared to indicate a strict hop.

Reserved
Zero on transmission. Ignored on receipt.

AS Number
Autonomous System number

4.7.4. ER-Hop 4: LSPID

The TS SC has an associated tolerance LSPID is used to identify the burstiness of arriving tunnel ingress point as the next
hop in the ER. This ER-Hop allows for stacking new CR-LSPs within an
already established CR-LSP. It also allows for splicing the CR-LSP

CR-LDP Specification - 16 22 - Exp. Apr August 1999

user datagrams. This tolerance is

being established with an existing CR-LSP.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| 0x804 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Reserved | Local LSPID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ingress LSR Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U bit
Unknown TLV bit. As defined by in [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

Type
LSPID 0x804

Length
Specifies the traffic parameter
Committed Burst Tolerance (CBT).

Ideally, a TS CRLSP request carries with it a rich set length of three
traffic parameters (PDR, CDR, and CBT) that accurately describe its
traffic characteristics. This allows the network value field in bytes.

L Bit
Set to perform resource
reservation, traffic shaping, and traffic policing.

However, for the sake of simplicity of the service definition, the
CDR is the only parameter that MUST always be specified for indicate Loose hop.
Cleared to indicate a TS
CRLSP. strict hop.

Reserved
Zero on transmission. Ignored on receipt.

Local LSPID
A peak data rate parameter (PDR) and a CBT are optional
traffic parameters for 2 byte field indicating the TS SC.

The network should make every effort LSPID which is unique
with reference to preserve ordering the its Ingress LSR.

Ingress LSR Router ID
A 4 byte field indicating the Ingress LSR ID.

4.8. Processing of the
delivered datagrams Explicit Route TLV

4.8.1. Selection of the next hop

A Label Request Message containing a TS CRLSP.

Network traffic that requires explicit route TLV must
determine the next hop for this path. Selection of this next hop may
involve a low packet loss ratio at selection from a given CDR
but set of possible alternatives. The
mechanism for making a selection from this set is not particularly sensitive to delay implementation
dependent and jitter (e.g., network
control traffic) is suited to the TS SC. The selection outside of the TS SC scope of this specification.
Selection of particular paths is used to signal to the various nodes along also outside of the path scope of this
specification, but it is assumed that the
queuing and scheduling mechanisms used to handle the CRLSP should
provide each node will make a low packet loss ratio.

5.3 Delay Sensitive (DS)

In the service model for the Delay Sensitive SC, the network commits best
effort attempt to deliver with high probability user datagrams at a rate of CDR
(Committed Data Rate) with minimum delay and delay variation. The
user MUST transmit data at determine a rate of CDR or lower in order to be
eligible for DS service. Datagrams in excess of CDR loop-free path. Note that such best

CR-LDP Specification - 23 - Exp. August 1999

efforts may be discarded overridden by local policy.

To determine the network. If next hop for the user sends at path, a rate of CDR or lower node performs the
network commits to deliver with high probability all user datagrams
with low delay and delay variation. If following
steps:

1) The node receiving the user sends at a rate
higher than CDR Label Request Message must first
evaluate the network does first ER-Hop. If the L bit is not provide any guarantees on set in the
excess traffic.

The Delay Sensitive SC has an associated tolerance to first
ER-Hop and if the burstiness
of arriving user datagrams. This tolerance node is defined not part of the abstract node described
by the traffic
parameter Committed Burst Tolerance (CBT).

Ideally, a DS CRLSP request carries with first ER-Hop, it has received the message in error, and
should return a rich "Bad initial ER-Hop" error. If the L bit is set of three
traffic parameters (PDR, CDR,
and CBT) the local node is not part of the abstract node described by
the first ER-Hop, the node selects a next hop that accurately describe its
traffic characteristics. This allows is along the network
path to perform resource
reservation, traffic shaping and policing.

However, for the sake of simplicity of the service definition, abstract node described by the
CDR first ER-Hop. If there
is no first ER-Hop, the only parameter that MUST always be specified for a DS
CRLSP. A peak data rate parameter (PDR) message is also in error and the system
should return a CBT are optional
traffic parameters for "Bad Explicit Routing TLV" error.

2) If there is no second ER-Hop, this indicates the DS SC. end of the
explicit route. The network explicit route TLV should make every effort to preserve ordering of be removed from the

CR-LDP Specification - 17 - Exp. Apr 1999

delivered datagrams
Label Request Message. This node may or may not be the end of the
LSP. Processing continues with section 4.8.2, where a DS CRLSP.

Network traffic that requires new
explicit route TLV may be added to the Label Request Message.

3) If the node is also a low delay part of the abstract node described by
the second ER-Hop, then the node deletes the first ER-Hop and delay variation at a
given CDR (e.g., voice traffic) is suited to
continues processing with step 2, above. Note that this makes the DS SC. The selection
second ER-Hop into the first ER-Hop of the DS SC next iteration.

4) The node determines if it is used to signal topologically adjacent to the various nodes along
abstract node described by the path
that second ER-Hop. If so, the queuing and scheduling mechanisms used to handle node
selects a particular next hop which is a member of the CRLSP
should provide low delay and delay variation.

5.4 Traffic Parameters

The CRLSP traffic parameters are defined in this section. abstract
node. The traffic parameters CDR, CBT node then deletes the first ER-Hop and PDR are defined in terms of continues
processing with section 4.8.2.

5) Next, the node selects a
TOKEN_BUCKET_TSPEC as specified in [RFC2215]. The following mapping next hop within the abstract node of parameters in
the TOKEN_BUCKET_TSPEC is used:

Token rate, r = CDR
Bucket depth, b = CBT
Peak traffic rate, p = PDR
Minimum policed unit, m = 1
Maximum packet size, M = MTU

The Traffic Parameters TLV first ER-Hop that is used to signal the traffic
characteristics of along the CRLSP. These traffic parameters are used path to
perform functions such as resource reservation, Shaping, and
Policing. See [SIN] for more details. The encoding for the Traffic
Parameters TLV is:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Traffic TLV (0x0810) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PDR TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CDR TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CBT TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.4.1 Peak data rate (PDR) TLV

The value of traffic parameter PDR abstract node of
the second ER-Hop. If no such path exists then there are two
cases:

5a) If the second ER-Hop is given as a positive integer in
bytes per second. Zero strict ER-Hop, then there is not an
error and the node should return a valid value of PDR.

The user may specify "Bad strict node" error.

5b) Otherwise, if the value of PDR depending second ER-Hop is a loose ER-Hop, then the SC of
node selects any next hop that is along the CRLSP.
Specifying path to the PDR allows next
abstract node. If no path exists within the network to use traffic management
functions such as shaping. MPLS domain, then
there is an error, and the node should return a "Bad loose node"
error.

6) Finally, the node replaces the first ER-Hop with any ER-Hop
that denotes an abstract node containing the next hop. This is
necessary so that when the explicit route is received by the next
hop, it will be accepted.

CR-LDP Specification - 18 24 - Exp. Apr August 1999

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| PDR

7) Progress the Label Request Message to the next hop.

4.8.2. Adding ER-Hops to the explicit route TLV (0x0811) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PDR

After selecting a next hop, the node may alter the explicit route in Bytes/sec |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.4.2. Committed Data Rate (CDR)

The value
the following ways.

If, as part of traffic parameter CDR executing the algorithm in section 4.8.1, the explicit
route TLV is given as removed, the node may add a positive integer in
bytes per second. Zero new explicit route TLV.

Otherwise, if the node is not a valid value member of CDR.

The user may provide the abstract node for the first
ER-Hop, then a requested value series of CDR ER-Hops may be inserted before the first
ER-Hop or may replace the first ER-Hop. Each ER-Hop in this series
must denote an abstract node that is a subset of the CRLSP request
depending on current abstract
node.

Alternately, if the SC first ER-Hop is a loose ER-Hop, an arbitrary
series of ER-Hops may be inserted prior to the CRLSP. first ER-Hop.

4.9 Route Pinning TLV

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| CDR TLV (0x0812) 0x823 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CDR in Bytes/sec
|P| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.4.3. Committed Burst Tolerance (CBT)

The value of traffic parameter CBT is given

U bit
Unknown TLV bit. As defined in bytes. Zero is not a
valid value of CBT.

The requested value of CBT MUST be no smaller than [LDP].

F bit
Forward unknown TLV bit. As defined in [LDP].

Type
Pinning-TLV type 0x823

Length
Specifies the MTU length of the
originating interface.

The user may provide a requested value of CBT field in the CRLSP request.
If the user chooses not bytes.

P Bit
The P bit is set to specify a 1 to indicate that route pinning is requested.
The P bit is set to 0 to indicate that route pinning is not
requested value of CBT and the
network

Reserved
Zero on transmission. Ignored on receipt.

4.10 CRLSP FEC Element

CR-LDP Specification - 25 - Exp. August 1999

A new FEC element is policing the traffic, then any excess traffic will introduced in this specification to support CR-
LSPs. The CRLDP FEC Element is an opaque FEC.

FEC Element Type Value
type name

CRLSP 0x04 No value; i.e., 0 value octets;
see below.

CRLSP FEC Element
To be
dropped by the network. used only in Messages of CR-LSPs.

The CR-LSP FEC TLV encoding is as follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| CBT TLV (0x0813) FEC(0x0100) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CBT in Bytes CR-LSP (4) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6. Open Issues

This section captures the issues that need further study.

CR-LDP Specification - 19 - Exp. Apr 1999

1) Review the FSM described in Appendix B and extend it by the CR-TLV
processing

U bit
Unknown TLV bit. As defined in Sections 4.8.1 and 4.8.2.

2) Consider if all three traffic parameters have to be signaled at
all times and if the network should supply default values for the
missing parameters.

3) Consider the following extensions to the CR-TLV:

3.1) Changing the 'P' [LDP].

F bit to "next hop flag" and making it a 2-bit
wide field with the following values:

- 00 "local repair", which means if it belongs to a loosely
routed segment, and the LSR detects a next hop change, the LSR
will try to establish a new LSP from this point on and switch
it over to the new LSP when it is setup.

- 01 "global repair", which means when the LSR detects a next
hop change, the LSR will tear down the LSP, the ingress LSR
will try to reestablish another LSP through the new path.

- 10 "pinned", which means that the loosely routed segments
must remain pinned down.

- 11 Reserved.

3.2) Adding one more field "LSPID" before ER-Hop TLV. LSPID can
be used to identify a network wide unique CRLSP.

- The first 4 bytes carrying
Forward unknown TLV bit. As defined in [LDP].

Type
FEC TLV type 0x0100

Length
Specifies the ingress LSR IP address

- The second 4 bytes carrying length of the unique ID value assigned by
the ingress LSR.

4) Consider the following extension to the ER-Hop TLV:

For Type field, add one more type, LSPID, which means the current
CRLSP will go through another CRLSP which is identified with this
LSPID value:

Value field in bytes.

CR-LSP FEC Element Type
----- -----
4 LSPID

Extend processing
0x04

Reserved
Zero on transmission. Ignored on receipt.

4.11 Error subcodes

In the LSPID ER-Hop processing described above, certain errors need to be reported
as follows: If the type of ER-
Hop is LSPID, and the other end of this CRLSP is not part of the
constraint-based route TLV, add it to the constraint-based TLV
with L bit turned off.

5) Consider traffic parameter negotiation and Notification Message. This section defines the ability to change status
codes for the traffic parameters associated with an already established path errors described in this specification.

CR-LDP Specification - 20 26 - Exp. Apr August 1999

without tearing the old path down.

Status Code Type
-------------------------------------- ----------
Bad Explicit Routing TLV Error 0x04000001
Bad Strict Node Error 0x04000002
Bad Loose Node Error 0x04000003
Bad Initial ER-Hop Error 0x04000004
Resource Unavailable 0x04000005
Traffic Parameters Unavailable 0x04000006
Setup abort 0x04000007

5. Security

No security issues are discussed in this version of

Pre-emption has to be controlled by the draft.

8. MPLS domain.

Resource reservation requires the LSRs to have an LSP admission
control function.

Normal routing can be bypassed by Traffic Engineered LSPs.

6. Acknowledgments

The messages used to signal the CRLSP setup are based on the work
done by the [LDP] team. The Explicit Route object and procedures used
in this specification are based on [ER].

The authors would also like to acknowledge the careful review and
comments of Osama Aboul-Magd, Ken Hayward, Greg Wright, Geetha Brown, Brian Williams, Peter Ashwood-smith,
Paul Beaubien, Matthew Yuen, Liam Casey, and Ankur Anand.

7. References

[FRAME] Callon

[LDP] Andersson et al, "Framework for Multiprotocol Label Switching", "Label Distribution Protocol Specification"
work in progress (draft-ietf-mpls-framework-02), November 1997. (draft-ietf-mpls-ldp-03), Feb. 1999.

[ARCH] Rosen et al, "Multiprotocol Label Switching Architecture",
work in progress (draft-ietf-mpls-arch-02), July 1998.

[LDP] Andersson (draft-ietf-mpls-arch-04), Feb. 1999.

[FRAME] Callon et al, "Label Distribution Protocol Specification" "Framework for Multiprotocol Label Switching",
work in progress (draft-ietf-mpls-ldp-02.txt), (draft-ietf-mpls-framework-02), November
1997.

[TER] Awduche et al, "Requirements for Traffic Engineering Over
MPLS", work in progress (draft-ietf-mpls-traffic-eng-00),
August 1998.

[ER] Guerin et al, "Setting up Reservations on Explicit Paths
using RSVP", work in progress (draft-guerin-expl-path-rsvp-01.txt, (draft-guerin-expl-path-rsvp-
01)
November 1997.

[TER] Awduche et al, "Requirements for Traffic Engineering Over
MPLS", work in progress (draft-awduche-mpls-traffic-eng-00), April
1998.

CR-LDP Specification - 27 - Exp. August 1999

[VPN1] Heinanen et al, "MPLS Mappings of Generic VPN Mechanisms",
work in progress (draft-heinanen-generic-vpn-mpls-00),
August 1998.

[VPN2] Jamieson et al, "MPLS VPN Architecture" work in progress
(draft-jamieson-mpls-vpn-00), August 1998.

[RFC2215] S. Shenker and J. Wroclawski, General Characterization
Parameters for Integrated Service Network Elements, RFC 2215, Sep
1997.

[SIN] B. Jamoussi, N. Feldman, and L. Andersson, "MPLS Ships

[VPN3] T. Li, "CPE based VPNs using MPLS", work in the
Night with ATM", (draft-jamoussi-mpls-sin-00.txt), August progress (draft-
li-mpls-vpn-00.txt), October 1998.

[LDP-STATE] L. Wu, et. al., "LDP State Machine" work in progress
(draft-ietf-mpls-ldp-state-00), Feb 1999.

CR-LDP Specification - 21 28 - Exp. Apr August 1999

10.

8. Author Information

Osama S. Aboul-Magd Loa Andersson
Nortel Networks Director Bay Architecture Lab, EMEA Lab,EMEA
P O Box 3511 Station C Kungsgatan 34, PO Box 1788
Ottawa, ON K1Y 4H7 111 97 Stockholm, Sweden
Canada phone: +46 8 441 78 34
phone: +1 613 763-5827 mobile +46 70 522 78 34
e-mail:
osama@NortelNetworks.com loa_andersson@baynetworks.com

Peter Ashwood-Smith Ross Callon
Nortel Networks IronBridge Networks
P O Box 3511 Station C 55 Hayden Avenue,
Ottawa, ON K1Y 4H7 Lexington, MA 02173
Canada Phone: +1-781-402-8017
Email:
phone: +1 613 763-4534 rcallon@ironbridgenetworks.com
petera@NortelNetworks.com

Ram Dantu Paul Doolan
Alcatel USA Inc. Ennovate Networks
IP Competence Center 330 Codman Hill Rd
1201 E. Campbell Road.,446-315 Marlborough MA 01719
Richadson, TX USA., 75081-2206 Phone: 978-263-2002
Phone: 972 996 2938 pdoolan@ennovatenetworks.com
Fax: 972 996 5902
Email:
ram.dantu@aud.alcatel.com

Paul Doolan
Ennovate Networks
330 Codman Hill Rd
Marlborough MA 01719
Phone: 978-263-2002
email: pdoolan@ennovatenetworks.com

Nancy Feldman Andre Fredette
IBM Corp. Nortel Networks
17 Skyline Drive
Hawthorne NY 10532
Phone: 914-784-3254
email: nkf@us.ibm.com

Andre Fredette
Nortel Networks 3 Federal Street
Hawthorne NY 10532 Billerica, MA 01821
email:
Phone: 914-784-3254 fredette@baynetworks.com
nkf@us.ibm.com

Eric Gray Joel M. Halpern
Lucent Technologies, Inc Newbridge Networks Inc.
1600 Osgood St. 593 Herndon Parkway
North Andover, MA 01847
email: ewgray@lucent.com

CR-LDP Specification - 22 - Exp. Apr 1999

Joel M. Halpern
Newbridge Networks Inc.
593 Herndon Parkway Herndon, VA 20170
email: jhalpern@newbridge.com
Phone: 603-659-3386 phone: 1-703-736-5954
fax: 1-703-736-5959
ewgray@lucent.com jhalpern@newbridge.com

Juha Heinanen Fiffi Hellstrand
Telia Finland, Inc. Ericsson Telecom AB
Myyrmaentie 2 S-126 25 STOCKHOLM
01600 VANTAA Sweden
Finland Tel: +46 8 719 4933
Tel: +358 303 944 808
Email: 41 500 4808 etxfiff@etxb.ericsson.se
jh@telia.fi

CR-LDP Specification - 29 - Exp. August 1999

Bilel Jamoussi Timothy E. Kilty
Nortel Networks Northchurch Communications
P O Box 3511 Station C 5 Corporate Drive,
Ottawa, ON K1Y 4H7
Canada
phone: +1 613 765-4814
email: jamoussi@NortelNetworks.com

Timothy E. Kilty
Northchurch Communications
5 Corporate Drive, Andover, MA 018110
Canada phone: 978 691-4656
Email:
phone: +1 613 765-4814 tkilty@northc.com
jamoussi@NortelNetworks.com

Andrew G. Malis
Ascend Communications, Inc.
1 Robbins Road
Westford, MA 01886
phone: 978 952-7414
fax: 978 392-2074
Email: malis@ascend.com Muckai K Girish
Ascend Communications, Inc. SBC Technology Resources, Inc.
1 Robbins Road 4698 Willow Road
Westford, MA 01886 Pleasanton, CA 94588
phone: 978 952-7414 Phone: (925) 598-1263
fax: 978 392-2074 Fax: (925) 598-1321
Email:
malis@ascend.com mgirish@tri.sbc.com

Kenneth Sundell
Ericsson
SE-126 25 Stockholm
Sweden

CR-LDP Specification - 23 - Exp. Apr 1999

email: kenneth.sundell@etx.ericsson.se Pasi Vaananen
Ericsson Nokia Telecommunications
SE-126 25 Stockholm 3 Burlington Woods Drive, Suite 250
Sweden Burlington, MA 01803
kenneth.sundell@etx.ericsson.se Phone: +1-781-238-4981
Email:
pasi.vaananen@ntc.nokia.com

Tom Worster Liwen Wu
General DataComm, Inc. Alcatel U.S.A
5 Mount Royal Ave.
Marlboro MA 01752
Email: tom.worster@gdc.com

Liwen Wu
Alcatel U.S.A 44983 Knoll Square
Marlboro MA 01752 Ashburn, Va. 20147
tom.worster@gdc.com USA
Phone: (703) 724-2619
FAX: (703) 724-2005
Inet:
liwen.wu@adn.alcatel.com

CR-LDP Specification - 30 - Exp. August 1999

Appendix A: CRLSP Establishment Examples

A.1 Strict Constraint-Based Explicit Route Example

This appendix provides an example for the setup of a strictly routed
CRLSP. In this example, each abstract node is represented by a
specific node.

The sample network used here is a four node network with two edge
LSRs and two core LSRs as follows:

a b c
LSR1------LSR2------LSR3------LSR4

LSR1 generates a Label Request Message as described in Section 3.1 of
this draft and sends it to LSR2. This message includes the CR-TLV.

The CR-TLV ER-TLV is composed by a vector of three ER-Hop TLVs <a, b, c>.
The ER-Hop TLVs used in this example are of type 0x01 0x0801 (IPv4 prefix)
with a prefix length of 32. Hence, each ER-Hop TLV identifies a
specific node as opposed to a group of nodes.

At LSR2, the following processing of the CR-TLV ER-TLV per Section 4.8.1 of
this draft takes place:

1) The first hop <a> is part of the abstract node LSR2. Therefore,
the first step passes the test. Go to step 2.

CR-LDP Specification - 24 - Exp. Apr 1999

2) There is a second ER-Hop, . Go to step 3.

3) LSR2 is not part of the abstract node described by the second
ER-Hop . Go to Step 4.

4) LSR2 determines that it is topologically adjacent to the
abstract node described by the second ER-Hop . LSR2 selects a
next hop (LSR3) which is the abstract node. LSR2 deletes the first
ER-Hop <a> from the CR-TLV ER-TLV which now becomes . Go to
Section 4.8.2.

At LSR2, the following processing of Section 4.8.2 takes place:

Executing algorithm 4.8.1 did not result in the removal of the
CR-TLV.
ER-TLV.

Also, LSR2 is not a member of the abstract node described by the
first ER-Hop .

Finally, the first ER-Hop is a strict hop.

Therefore, processing section 4.8.2 does not result in the
insertion of new ER-Hops. The selection of the next hop has been

CR-LDP Specification - 31 - Exp. August 1999

already done is step 4 of Section 4.8.1 and the processing of the
CR-TLV
ER-TLV is completed at LSR2. In this case, the Label Request
Message including the CR-TLV ER-TLV <b, c> is progressed by LSR2 to LSR3.

At LSR3, a similar processing to the CR-TLV ER-TLV takes place except that
the incoming CR-TLV ER-TLV = <b, c> and the outgoing CR-TLV ER-TLV is <c>.

At LSR4, the following processing of section 4.8.1 takes place:

1) The first hop <c> is part of the abstract node LSR4. Therefore,
the first step passes the test. Go to step 2.

2) There is no second ER-Hop, this indicates the end of the CRLSP.
The CR-TLV ER-TLV is removed from the Label Request Message. Processing
continues with Section 4.8.2.

At LSR4, the following processing of Section 4.8.2 takes place:

Executing algorithm 4.8.1 resulted in the removal of the CR-TLV. ER-TLV.
LSR4 does not add a new CR-TLV. ER-TLV.

Therefore, processing section 4.8.2 does not result in the
insertion of new ER-Hops. This indicates the end of the CRLSP and
the processing of the CR-TLV ER-TLV is completed at LSR4.

At LSR4, processing of Section 3.2 is invoked. The first condition is
satisfied (LSR4 is the egress end of the CRLSP and upstream mapping
has been requested). Therefore, a Label Mapping Message is generated

CR-LDP Specification - 25 - Exp. Apr 1999
by LSR4 and sent to LSR3.

At LSR3, the processing of Section 3.2 is invoked. The second
condition is satisfied (LSR3 received a mapping from its downstream
next hop LSR4 for a CRLSP for which an upstream request is still
pending). Therefore, a Label Mapping Message is generated by LSR3 and
sent to LSR2.

At LSR2, a similar processing to LSR 3 takes place and a Label
Mapping Message is sent back to LSR1 which completes the end-to-end
CRLSP setup.

A.2. Node Groups and Specific Nodes Example

A request at an ingress LSR to setup a CRLSP might originate from a
management system or an application, the details are implementation
specific.

The ingress LSR uses information provided by the management system or
the application and possibly also information from the routing
database to calculated the constraint-based explicit route and to create the Label
Request Message.

CR-LDP Specification - 32 - Exp. August 1999

The Label request message carries together with other necessary
information a CR-TLV ER-TLV defining the constraint-based explicitly routed path. In our
example the list of hops in the ER-Hop TLV is supposed to contain an
abstract node representing a group of nodes, an abstract node
representing a specific node, another abstract node representing a
group of nodes, and an abstract node representing a specific egress
point.

In--{Group 1}--{Specific A}--{Group 2}--{Specific Out: B}

The CR-TLV ER-TLV contains four ER-Hop TLVs:

1. An ER-Hop TLV that specifies a group of LSR valid for the first
abstract node representing a group of nodes (Group 1).

2. An ER-Hop TLV that indicates the specific node (Node A).

3. An ER-Hop TLV that specifies a group of LSRs valid for the
second abstract node representing a group of nodes (Group 2).

4. An ER-Hop TLV that indicates the specific egress point for the
CRLSP (Node B).

All the ER-Hop TLVs are strictly routed nodes.

The setup procedure for this CRLSP works as follows:

CR-LDP Specification - 26 - Exp. Apr 1999

1. The ingress node sends the Label Request Message to a node that
is a member the group of nodes indicated in the first ER-Hop TLV,
following normal routing for the specific node (A).

2. The node that receives the message identifies itself as part of
the group indicated in the first ER-Hop TLV, and that it is not
the specific node (A) in the second. Further it realizes that the
specific node (A) is not one of its next hops.

3. It keeps the ER-Hop TLVs intact and sends a Label Request
Message to a node that is part of the group indicated in the first
ER-Hop TLV (Group 1), following normal routing for the specific
node (A).

4. The node that receives the message identifies itself as part of
the group indicated in the first ER-Hop TLV, and that it is not
the specific node (A) in the second ER-Hop TLV. Further it
realizes that the specific node (A) is one of its next hops.

5. It removes the first ER-Hop TLVs and sends a Label Request
Message to the specific node (A).

6. The specific node (A) recognizes itself in the first ER-Hop
TLV. Removes the specific ER-Hop TLV.

CR-LDP Specification - 33 - Exp. August 1999

7. It sends a Label Request message Message to a node that is a member of
the group (Group 2) indicated in the ER-Hop TLV.

8. The node that receives the message identifies itself as part of
the group indicated in the first ER-Hop TLV, further it realizes
that the specific egress node (B) is one of its next hops.

9. It sends a Label Request message Message to the specific egress node
(B).

10. The specific egress node (B) recognizes itself as the egress
for the CRLSP, it returns a Label Mapping Message, that will
traverse the same path as the Label Request Message in the
opposite direction.

CR-LDP Specification - 27 - Exp. Apr 1999

Appendix B. CR-LDP Finite State Machine

In this description of the CR-LDP FSM, behavior relating to the
state of LDP messages is assumed to be defined (implicitly or
explicitly) in [LDP]. In particular, LDP is assumed to retain
state information relating a Label Request made of a downstream
neighbor to the Label Request message(s) of upstream neighbors
(downstream-on-demand mode) which the (downstream) Label Request
is meant to satisfy. This will be true of many potential
applications of LDP, of which CR-LDP is an example. Minimally,
this state should include message IDs of Label Requests (both sent
and received) and the LSR(s) from which pending Label Request(s)
were received.

The FSM describes CR-LDP behavior in the following operations:

- Start of CRLSP setup (in which a Label Request is sent);

- Processing the CR-TLV portion of Label Requests;

- Completion of CRLSP setup (via Label Mapping messages);

- Notification of originator when:

- a loop is detected in a loose constraint-based route segment,

- an ER-Hop is not reachable from a previous ER-Hop,

- a next ER-Hop is strict and not directly connected to the
current LSR or

- the current LSR is strict and is not (part of the abstract
node in) the first ER-Hop in the CR-TLV;

- Withdrawing a CRLSP.

For the description, the following pictorial representations may be
used as an aid to understanding:

LSR 1 LSR 2 ... LSR n

.-----. .-----. .-----.
| ER | | ER | | ER |
`-----' `-----' `-----'
| CR-TLV CR-TLV ^ | CR-TLV CR-TLV ^
| Next | | Next |
| Hop | | Hop |
V | V |
.-----. Label .-----. the CRLSP, it returns a Label Mapping Message, that will
traverse the same path as the Label .-----.
| LDP |----------->| LDP |-------> ... ------->| LDP |
`-----' Request `-----' Request Request `-----' Message in the
opposite direction.

CR-LDP Specification - 28 34 - Exp. Apr August 1999

CRLSP Setup propagation

LSR 1 LSR 2 ... LSR n

.-----. .-----. .-----.
| ER | | ER | | ER |
`-----' `-----' `-----'
^ Status Status |
| Previous |
| Hop |
| V
.-----. Label .-----. Label Label .-----.
| LDP |<-----------| LDP |<------- ... <-------| LDP |
`-----' Mapping `-----' Mapping Mapping `-----'

CRLSP Status propagation

.---------------.
| ER | .---------------.
| Link/Call | | LDP |
| Admission | | |
| Control | | Label |
`---------------' | Allocation |
`---------------'

Related Tasks

B.1. CR-LDP Primitives

The following sections describe

Appendix B. QoS Service Examples

B.1 Service Examples

Construction of an end-to-end service is the logical interactions between
Constrain-based Route and LDP state machines in terms result of
primitives the rules
enforced at the edge and the treatment that describe packets receive at the minimal information exchange
required. These assume an asynchronous exchange model involving
locally significant IDs
network nodes. The rules define the traffic conditioning actions that is used
are implemented at the edge and they include policing with pass,
mark, and drop capabilities. The edge rules are expected to tie status be
defined by the mutual agreements between the service providers and
their customers and they will constitute an essential part of the
SLA. Therefore edge rules are not included in the signaling protocol.

Packets treatment at a request network node is usually referred to as the initial setup and to allow LDP to relate incoming/outgoing
Label Request messages. A synchronous model - possibly based on
multiple threads -
local behavior. Local behavior could be specified in many ways. One
example for local behavior specification is also possible the service frequency
introduced in section 4.3.2.1., together with the resource
reservation rules implemented at the nodes.

Edge rules and would eliminate local behaviors can be viewed as the need main building
blocks for IDs.

B.1.1. CR to LDP Primitives

LDP_SEND_REQ( TLV_List, To_LSR, Identifier )

TLV_List

TLVs to be sent to a neighboring LSR; includes at least an the end-to-end service construction. The following table
illustrates the applicability of the building block approach for
constructing different services including those defined for ATM.

Service PDR PBS CDR CBS EBS Service Conditioning
Examples Frequency Action
---------------------------------------------------------------------------

DS S S =PDR =PBS 0 Frequent drop>PDR

TS S S S S 0 Unspecified drop>PDR,PBS
mark>CDR,CBS

BE inf inf inf inf 0 Unspecified -

FRS S S CIR ~B_C ~B_E Unspecified drop>PDR,PBS
mark>CDR,CBS,EBS

ATM-CBR PCR CDVT =PCR =CDVT 0 VeryFrequent drop>PCR

ATM-VBR.3(rt) PCR CDVT SCR MBS 0 Frequent drop>PCR
mark>SCR,MBS

ATM-VBR.3(nrt) PCR CDVT SCR MBS 0 Unspecified drop>PCR
mark>SCR,MBS

ATM-UBR PCR CDVT - - 0 Unspecified drop>PCR

ATM-GFR.1 PCR CDVT MCR MBS 0 Unspecified drop>PCR

CR-LDP Specification - 29 35 - Exp. Apr August 1999

CR-TLV and may contain additional TLVs (i.e. QoS TLVs).

To_LSR

The neighbor LSR

ATM-GFR.2 PCR CDVT MCR MBS 0 Unspecified drop>PCR
mark>MCR,MFS

int-serv-CL p m r b 0 Frequent drop>p
drop>r,b

S= User specified

In the above table, the DS refers to which a Label Request is delay sensitive service where
the network commits to deliver with high probability user datagrams
at a rate of PDR with minimum delay and delay requirements. Datagrams
in excess of PDR will be sent.

Identifier

Locally significant unique identifier. May be used discarded.

The TS refers to
associate a generic throughput sensitive service where the Label Request
network commit to be sent either deliver with high probability user datagrams at a Label
Request that was previously received (e.g. - LSR 2 above)
or
rate of at least CDR. The user may transmit at a subsequent CRLSP Status (e.g. - LSR 1 above).

LDP_SEND_RSP( Status, Identifier )

Status

Status rate higher than CDR
but datagrams in excess of CDR would have a specific CRLSP Setup Request. A Status lower probability of zero
indicates success; other Status values
being delivered.

The BE is the best effort service and it implies that there are given in Error
Subcodes section. This Status no
expected service guarantees from the network.

B.2. Establishing CR-LSP Supporting Real-Time Applications

In this scenario the customer needs to establish an LSP for
supporting real-time applications such voice and video. The Delay-
sensitive (DS) service is carried requested in Label Mapping or
Notification messages to this case.

The first step is the originator specification of the CRLSP setup.

Identifier

Locally significant unique identifier used to associate traffic parameters in the
Label Mapping to be sent with a Label Request received (e.g.
LSR n above).

B.1.2. LDP to CR Primitives

CR_RECEIVED_REQ( TLV_List, Identifier )

TLV_List

TLVs
signaling message. The two parameters of interest to the DS service
are the PDR and the PBS and their values are specified by the user
based on his requirements. Since all the traffic parameters are
included in the signaling message, appropriate values must be processed by
assigned to all of them. For DS service, the local constraint-based route
function.

Identifier

Locally significant unique identifier used CDR and the CBS values
are set equal to associate the
received request either with a subsequent further request
or a response. For example, PDR and the identifier provided here
would be used in a subsequent LDP_SEND_REQ or LDP_SEND_RSP.

CR_LSP_STATUS( Status, Identifier )

Status

Status of a specific CRLSP Setup Request. A Status PBS respectively. An indication of zero
indicates success; other Status
whether the parameter values are given in section
Error Subcodes. This Status originated at the remote LSR

CR-LDP Specification - 30 - Exp. Apr 1999

which either completed subject to negotiation is flagged.

The transport characteristics of the CRLSP setup or determined DS service requires that
CRLSP setup could not
Frequent frequency to be done.

Identifier

Locally significant unique identifier used requested to associate reflect the
received response with real-time delay
requirements of the original request. For example,
this identifier would be service.

In addition to the same as was used in transport characteristics, both the initial
LDP_SEND_REQ.

B.2. CR-LDP States

This document defines 3 states relative to any one specific CRLSP.
They are:

CR_Non_Existant - no state information exists relative network
provider and the customer need to this
CRLSP;

CR_In_Progress - LDP_SEND_REQ has been called in result agree on the actions enforced at
the edge. The specification of external input (e.g. - management);

CR_Established - a successful status has been received from
an earlier setup.

These states are defined such that no additional state those actions is required expected to support CRLSPs using LDP at intermediate LSRs than is already
required in LDP.

B.3. CR-LDP Events

This document defines 4 events impacting any one specific CRLSP.
They are:

CR_Start - be a CRLSP is required based on an external stimulus
(e.g. - management);

CR_Req_Received - further CRLSP setup processing part
of the service level agreement (SLA) negotiation and is required
based on CR_RECEIVED_REQ (i.e. - from an upstream LSR's CRLSP
Label Request);

CR_Setup_Complete - CRLSP setup has been successfully completed
based on CR_LSP_STATUS (with success status);

CR_LSP_Failure - Either a CRLSP could not included
in the signaling protocol. For DS service, the edge action is to drop
packets that exceed the PDR and the PBS specifications.

The signaling message will be sent in the direction of the ER path
and the LSP is established as
requested, or a setup CRLSP has dropped; based on CR_LSP_STATUS
(with error status).

B.4. CR-LDP Transitions

State transitions are defined as follows: following the normal LDP procedures. Each

CR-LDP Specification - 31 36 - Exp. Apr August 1999

State Event Action New State
==================== ================= ====== ===============
CR_Non_Existant CR_Start 1 CR_In_Progress
CR_Non_Existant CR_Req_Rec 2 CR_Non_Existant
CR_In_Progress CR_Setup_Complete CR_Established
CR_In_Progress CR_LSP_Failure 3 CR_Non_Existant
CR_Established CR_LSP_Failure 3 CR_Non_Existant

Actions:

1) Establish CRLSP state, create CR-TLV information,
LDP_SEND_REQ.
2) Process CR-TLV (as described in "Processing of
the Constraint-Based Route TLV" section)

LSR applies its admission control rules. If sufficient resources are
not available and the parameter values are subject to negotiation,
then the LSR could negotiate down either
LDP_SEND_REQ the PDR, the PBS, or LDP_SEND_RSP.
3) Remove state information relative both.
The new parameters values are echoed back in the Label Mapping
Message. LSRs might need to re-adjust their resource reservations
based on the new traffic parameter values.

B.3. Establishing CR-LSP Supporting Delay Insensitive Applications

In this CRLSP (may notify
management, other external source initially requiring
setup). example we assume that a throughput sensitive (TS) service is
requested. For resource allocation the purposes of this transition table, illegal transitions
(not included user assigns values for PDR,
PBS, CDR, and CBS. The negotiation flag is set if the traffic
parameters are subject to negotiation.

Since the service is delay insensitive by definition, the Unspecified
frequency is signaled to indicate that the service frequency is not
an issue.

Similar to the previous example, the edge actions are not subject for
signaling and are specified in the table) service level agreement between
the user and the network provider.

For TS service, the edge rules might include marking to indicate high
discard precedence values for all packets that exceed CDR and the
CBS. The edge rules will also include dropping of packets that are do
not conform to either PDR and PBS.

Each LSR of the LSP is expected to run its admission control rules
and negotiate traffic parameters down if sufficient resources do not
exist. The new parameters values are ignored. echoed back in the Label Mapping
Message. LSRs might need to re-adjust their resources based on the
new traffic parameter values.