MPLS Working Group Bilel Jamoussi, Editor
Internet Draft Nortel Networks
Expiration Date: August 1999
February 1999
Constraint-Based LSP Setup using LDP
draft-ietf-mpls-cr-ldp-01.txt
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Copyright Notice
Copyright (C) The Internet Society (1998). All Rights Reserved.
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 explicit route constraints, QoS constraints, and
others. Constraint-based routing (CR) 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).
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Other uses exist for CRLSPs as well ([VPN1], [VPN2] and [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 ......................................... 3
2. Constraint-based Routing Overview .................... 3
2.1 Strict and Loose Explicit Routes ..................... 4
2.2 Traffic Characteristics .............................. 4
2.3 Pre-emption .......................................... 5
2.4 Route Pinning ........................................ 5
2.5 Resource Class ....................................... 5
3. Solution Overview .................................... 5
3.1 Required Messages and TLVs ........................... 7
3.2 Label Request Message ................................ 7
3.3 Label Mapping Message ................................ 8
3.4 Notification Message ................................. 9
3.5 Release & Withdraw Messages .......................... 9
4. Protocol Specification .............................. 9
4.1 Explicit Route TLV (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 ................................ 16
4.3.2.2 Label Mapping Message ................................ 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 ER-TLV ............................. 22
4.8.1 Selection of the next hop ............................ 22
4.8.2 Adding the Label Request Message to the next hop ..... 24
4.9 Route Pinning TLV ................................... 24
4.10 CR-LSP FEC Element ................................... 24
4.11 Error Subcodes ...................................... 25
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5. Security Considerations .............................. 26
6. Acknowledgement ...................................... 26
7. References ........................................... 26
8. Author Information ................................... 28
Appendix A CRLSP Establishment Examples ......................... 30
A.1 Strict Explicit Route Example ........................ 30
A.2 Node Groups and 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 need for constraint-based routing (CR) in MPLS has been explored
elsewhere [ARCH], [FRAME], and [TER]. 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, a
decision was made that support for explicit path setup in LDP will be
moved to a separate document. This document provides that support and
it has been accepted as a working document in the Orlando meeting.
This specification proposes 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
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 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 a mechanism that supports the Traffic
Engineering requirements defined in [TER]. Explicit Routing is a
subset of the more general constraint-based routing where the
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constraint is the explicit route (ER). Other constraints are defined
to provide a network operator with control over the path taken by an
LSP. This section is an overview of the various constraints supported
by this specification.
2.1 Strict and Loose Explicit Routes
Like any other LSP an CRLSP is a path through an MPLS 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 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 in order to better support
the traffic sent over the LSP. The reason 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.
An explicit route is represented in a 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 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 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 including all of the identified groups of nodes.
To simplify the discussion, we call each group of nodes an abstract
node. Thus, we can also say that a constraint-based route is a path
including all of the abstract nodes, with the specified operations
occurring along that path.
2.2 Traffic Characteristics
The traffic characteristics of a path are described in the Traffic
Parameters TLV in terms of a peak rate, committed rate, and service
granularity. The peak and committed rates describe the bandwidth
constraints of a path while the service granularity can be used to
specify a constraint on the delay variation that the CRLDP MPLS
domain may introduce to a path's traffic.
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2.3 Pre-emption
CR-LDP signals the resources required by a path on each hop of the
route. If a route with sufficient resources can not be found,
existing paths may be rerouted to reallocate resources to the new
path. This is the process of path pre-emption. Setup and holding
priorities are used to rank existing paths (holding priority) and the
new path (setup priority) to determine if the new path can pre-empt
an existing path.
The setupPriority of a new CRLSP and the holdingPriority attributes
of the existing CRLSP are used to specify priorities. Signaling a
higher holding priority expresses that the path, once it has been
established, should have a lower chance of being pre-empted.
Signaling a higher setup priority expresses the expectation that, in
the case that resource are unavailable, the path is more likely to
pre-empt other paths. The exact rules determining bumping are an
aspect of network policy.
The allocation of setup and holding priority values to paths is an
aspect of network policy.
The setup and holding priority values range from zero (0) to seven
(7). The 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 use of default
priority values is an aspect of network policy.
The setupPriority of a CRLSP should not be higher (numerically less)
than its holdingPriority since it might bump an LSP and be bumped by
next "equivalent" request.
2.4 Route Pinning
Route pinning is applicable to segments of an LSP that are loosely
routed - i.e. those segments which are specified with a next hop with
the 'L' bit set or where the next hop is an "abstract node". A CRLSP
may be setup using route pinning if it is undesirable to change the
path used by an LSP because a better next hop becomes available at
some LSR along the loosely routed portion of the LSP.
2.5 Resource Class
Network resources may be classified in various ways by the network
operator. These classes are also known as "colors" or "administrative
groups". When an CR-LSP is being established, it's necessary to
indicate which resource classes the CR-LSP can draw from.
3. Solution Overview
CRLSP over LDP Specification is designed with the following goals:
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1. Meet the requirements outlined in [TER] for performing traffic
engineering and provide a solid foundation for performing more
general constraint-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].
3. Keep the solution simple.
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 constraint-based routed LSPs in this specification
depends on the following minimal LDP behaviors as specified in [LDP]:
- Basic and/or Extended Discovery Mechanisms.
- Use the Label Request Message defined in [LDP] in downstream on
demand label advertisement mode with ordered control.
- Use the Label Mapping Message defined in [LDP] in downstream on
demand mode with ordered control.
- Use the Notification Message defined in [LDP].
- Use the Withdraw and Release Messages defined in [LDP].
- Use the Loop Detection (in the case of loosely routed segments
of a CRLSP) mechanisms defined in [LDP].
In addition, the following functionality is added to what's defined
in [LDP]:
- The Label Request Message used to setup a CRLSP includes one or
more CR-TLVs defined in Section 4. For instance, the Label Request
Message may include the ER-TLV.
- An LSR implicitly infers ordered control from the existence of
one or more CR-TLVs in the 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 Label
Request Message includes one or more of the CR-TLVs, then ordered
control is used to setup the CRLSP. Note that this is also true
for the loosely routed parts of a CRLSP.
- New status codes are defined to handle error notification for
failure of established paths specified in the CR-TLV.
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Examples of CRLSP establishment are given in Appendix A to illustrate
how the mechanisms described in this draft work.
3.1 Required Messages and TLVs
Any Messages, TLVs, and procedures not defined explicitly in this
document are defined in the [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 [LDP]
document and indication of additional functionality beyond what's
defined in [LDP] where necessary.
3.2 Label Request Message
The Label Request Message is as defined in 3.5.8 of [LDP] with the
following modifications (required only if any of the CR-TLVs is
included in the Label Request Message):
- Only a single FEC-TLV may be included in the Label Request
Message. The CR-LSP FEC TLV should be used.
- The Return Message ID TLV is MANDATORY.
- The Optional Parameters TLV includes the definition of any of
the Constraint-based TLVs specified in Section 4.
- The Procedures to handle the Label Request Message are augmented
by the procedures for processing of the CR-TLVs as defined in
Section 4.
The encoding for the CR-LDP Label Request Message is as follows:
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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 single Label-TLV may be included in the 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 Mapping message is transmitted by a downstream LSR to an upstream
LSR under one of the following conditions:
1. The LSR is the egress end of the CRLSP and an upstream mapping
has been requested.
2. The LSR received a mapping from its downstream next hop LSR for
an CRLSP for which an upstream request is still pending.
The encoding for the CR-LDP Label Mapping Message is as follows:
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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 Mapping (0x0400) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FEC TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Request Message ID TLV (mandatory) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSPID TLV (CR-LDP, mandatory) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic TLV (CR-LDP, optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.4 Notification Message
The Notification Message 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 are defined in Section 4.11 to signal
error notifications associated with the establishment of 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 LSPID
TLV.
4. Protocol Specification
The Label Request Messages defined in [LDP] optionally carries one or
more of the 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
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- 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| ER-TLV (0x0800) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ER-Hop TLV 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ER-Hop TLV 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 carrying the value of the 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 (ER-Hop TLV)
The contents of an ER-TLV are a series of variable length ER-Hop
TLVs. Each ER-Hop TLV has the form:
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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 contents of
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 L bit is an attribute of the ER-Hop. The L bit is set if the
ER-Hop represents a loose hop in the explicit route. If the bit is
not set, the ER-Hop represents a strict hop in the explicit route.
The L bit in the ER-Hop is a one-bit attribute. If the L bit is
set, then the value of the attribute is "loose." Otherwise, the
value 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 and strict nodes are always
interpreted relative to their prior abstract nodes.
The path between a strict node and its prior node MUST include
only network nodes from the strict node and 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 strict node or its prior
abstract node.
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Contents
A variable length field containing the node or abstract node that
is the consecutive nodes that make up the explicit routed LSP.
4.3 Traffic Parameters TLV
The following sections describe the CRLSP Traffic Parameters. The
required characteristics of a CRLSP are expressed by the Traffic
Parameter values.
A Traffic Parameters TLV, is used to signal the Traffic Parameter
values. The Traffic Parameters are defined in the subsequent
sections.
The Traffic Parameters TLV contains a Flags field, a Frequency, a
Weight, and the five Traffic Parameters PDR, PBS, CDR, CBS, EBS. The
Traffic Parameters TLV is 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 value of the ER-TLV type which
is 0x810.
Length
Specifies the length of the value field in bytes.
Flags
The Flags field is shown below:
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+--+--+--+--+--+--+--+--+
| Res |F6|F5|F4|F3|F2|F1|
+--+--+--+--+--+--+--+--+
Res - These bits are reserved.
Zero on transmission.
Ignored on receipt.
F1 - Corresponds to the PDR.
F2 - Corresponds to the PBS.
F3 - Corresponds to the CDR.
F4 - Corresponds to the CBS.
F5 - Corresponds to the EBS.
F6 - Corresponds to the Weight.
Each flag Fi is a Negotiable Flag corresponding to a 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 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 weight of the CRLSP.
Valid weight values are from 1 to 255. The value 0 means
that weight is not applicable for the CRLSP.
Traffic Parameters
Each Traffic Parameter is encoded as a 32 bit IEEE single-
precision floating point number. A value of positive infinity is
represented as an IEEE single-precision floating-point number with
an exponent of 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 greater than or equal to the value of CDR
in a correctly encoded Traffic Parameters TLV.
4.3.1 Semantics
4.3.1.1 Frequency
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The Frequency specifies at what granularity the CDR allocated to the
CRLSP is made available. The value VeryFrequently means that the
available rate should average at least the CDR when measured over any
time interval equal to or longer than the shortest packet time at the
CDR. The 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 CDR.
The value Unspecified means that the CDR MAY be provided at any
granularity.
4.3.1.2 Peak Rate
The Peak Rate defines the maximum rate at which traffic SHOULD be
sent to the CRLSP. The Peak Rate is useful for the purpose of
resource allocation. If resource allocation within the MPLS domain
depends on the Peak Rate value then it should be enforced at the
ingress to the MPLS domain.
The Peak Rate is defined in terms of the two Traffic Parameters PDR
and PBS, see section 4.3.1.5 below.
4.3.1.3 Committed Rate
The Committed Rate defines the rate that the MPLS domain commits to
be available to the CRLSP.
The Committed Rate is defined in terms of the two Traffic Parameters
CDR and CBS, see section 4.3.1.6 below.
4.3.1.4 Excess Burst Size
The Excess Burst Size may be used at 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:
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o If Tp(t)-B >= 0, the packet is not in excess of 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 positive infinite
value of 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
Jamoussi, et. al. February 25, 1999 [Page 15]
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.
Jamoussi, et. al. February 25, 1999 [Page 16]
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.
Jamoussi, et. al. February 25, 1999 [Page 17]
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
Jamoussi, et. al. February 25, 1999 [Page 18]
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].
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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.
Jamoussi, et. al. February 25, 1999 [Page 20]
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 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.
AS Number
Autonomous System number
4.7.4. ER-Hop 4: LSPID
The LSPID is used to identify the 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
Jamoussi, et. al. February 25, 1999 [Page 21]
CR-LDP Specification - 22 - Exp. August 1999
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 in [LDP].
F bit
Forward unknown TLV bit. As defined in [LDP].
Type
LSPID 0x804
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.
Local LSPID
A 2 byte field indicating the LSPID which is unique
with reference to the its Ingress LSR.
Ingress LSR Router ID
A 4 byte field indicating the Ingress LSR ID.
4.8. Processing of the Explicit Route TLV
4.8.1. Selection of the next hop
A Label Request Message containing a explicit route TLV must
determine the next hop for this path. Selection of this next hop may
involve a selection from a set of possible alternatives. The
mechanism for making a selection from this set is implementation
dependent and is outside of the scope of this specification.
Selection of particular paths is also outside of the scope of this
specification, but it is assumed that each node will make a best
effort attempt to determine a loop-free path. Note that such best
Jamoussi, et. al. February 25, 1999 [Page 22]
CR-LDP Specification - 23 - Exp. August 1999
efforts may be overridden by local policy.
To determine the next hop for the path, a node performs the following
steps:
1) The node receiving the Label Request Message must first
evaluate the first ER-Hop. If the L bit is not set in the first
ER-Hop and if the node is not part of the abstract node described
by the first ER-Hop, it has received the message in error, and
should return a "Bad initial ER-Hop" error. If the L bit is set
and the local node is not part of the abstract node described by
the first ER-Hop, the node selects a next hop that is along the
path to the abstract node described by the first ER-Hop. If there
is no first ER-Hop, the message is also in error and the system
should return a "Bad Explicit Routing TLV" error.
2) If there is no second ER-Hop, this indicates the end of the
explicit route. The explicit route TLV should be removed from the
Label Request Message. This node may or may not be the end of the
LSP. Processing continues with section 4.8.2, where a new
explicit route TLV may be added to the Label Request Message.
3) If the node is also a part of the abstract node described by
the second ER-Hop, then the node deletes the first ER-Hop and
continues processing with step 2, above. Note that this makes the
second ER-Hop into the first ER-Hop of the next iteration.
4) The node determines if it is topologically adjacent to the
abstract node described by the second ER-Hop. If so, the node
selects a particular next hop which is a member of the abstract
node. The node then deletes the first ER-Hop and continues
processing with section 4.8.2.
5) Next, the node selects a next hop within the abstract node of
the first ER-Hop that is along the path to the abstract node of
the second ER-Hop. If no such path exists then there are two
cases:
5a) If the second ER-Hop is a strict ER-Hop, then there is an
error and the node should return a "Bad strict node" error.
5b) Otherwise, if the second ER-Hop is a loose ER-Hop, then the
node selects any next hop that is along the path to the next
abstract node. If no path exists within the 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.
Jamoussi, et. al. February 25, 1999 [Page 23]
CR-LDP Specification - 24 - Exp. August 1999
7) Progress the Label Request Message to the next hop.
4.8.2. Adding ER-Hops to the explicit route TLV
After selecting a next hop, the node may alter the explicit route in
the following ways.
If, as part of executing the algorithm in section 4.8.1, the explicit
route TLV is removed, the node may add a new explicit route TLV.
Otherwise, if the node is a member of the abstract node for the first
ER-Hop, then a series of 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 current abstract
node.
Alternately, if the first ER-Hop is a loose ER-Hop, an arbitrary
series of ER-Hops may be inserted prior to the 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| 0x823 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
U bit
Unknown TLV bit. As defined in [LDP].
F bit
Forward unknown TLV bit. As defined in [LDP].
Type
Pinning-TLV type 0x823
Length
Specifies the length of the value field in bytes.
P Bit
The P bit is set to 1 to indicate that route pinning is requested.
The P bit is set to 0 to indicate that route pinning is not
requested
Reserved
Zero on transmission. Ignored on receipt.
4.10 CRLSP FEC Element
Jamoussi, et. al. February 25, 1999 [Page 24]
CR-LDP Specification - 25 - Exp. August 1999
A new FEC element is 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 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| FEC(0x0100) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CR-LSP (4) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
U bit
Unknown TLV bit. As defined in [LDP].
F bit
Forward unknown TLV bit. As defined in [LDP].
Type
FEC TLV type 0x0100
Length
Specifies the length of the value field in bytes.
CR-LSP FEC Element Type
0x04
Reserved
Zero on transmission. Ignored on receipt.
4.11 Error subcodes
In the processing described above, certain errors need to be reported
as part of the Notification Message. This section defines the status
codes for the errors described in this specification.
Jamoussi, et. al. February 25, 1999 [Page 25]
CR-LDP Specification - 26 - Exp. August 1999
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
Pre-emption has to be controlled by the 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 Ken Hayward, Greg Wright, Geetha Brown, Brian Williams,
Paul Beaubien, Matthew Yuen, Liam Casey, and Ankur Anand.
7. References
[LDP] Andersson et al, "Label Distribution Protocol Specification"
work in progress (draft-ietf-mpls-ldp-03), Feb. 1999.
[ARCH] Rosen et al, "Multiprotocol Label Switching Architecture",
work in progress (draft-ietf-mpls-arch-04), Feb. 1999.
[FRAME] Callon et al, "Framework for Multiprotocol Label Switching",
work in progress (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)
November 1997.
Jamoussi, et. al. February 25, 1999 [Page 26]
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.
[VPN3] T. Li, "CPE based VPNs using MPLS", work in 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.
Jamoussi, et. al. February 25, 1999 [Page 27]
CR-LDP Specification - 28 - Exp. August 1999
8. Author Information
Osama S. Aboul-Magd Loa Andersson
Nortel Networks Director Bay Architecture 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
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
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
ram.dantu@aud.alcatel.com
Nancy Feldman Andre Fredette
IBM Corp. Nortel Networks
17 Skyline Drive 3 Federal Street
Hawthorne NY 10532 Billerica, MA 01821
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 Herndon, VA 20170
Phone: 603-659-3386 phone: 1-703-736-5954
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 41 500 4808 etxfiff@etxb.ericsson.se
jh@telia.fi
Jamoussi, et. al. February 25, 1999 [Page 28]
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 Andover, MA 018110
Canada phone: 978 691-4656
phone: +1 613 765-4814 tkilty@northc.com
jamoussi@NortelNetworks.com
Andrew G. Malis 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
malis@ascend.com mgirish@tri.sbc.com
Kenneth Sundell 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
pasi.vaananen@ntc.nokia.com
Tom Worster Liwen Wu
General DataComm, Inc. Alcatel U.S.A
5 Mount Royal Ave. 44983 Knoll Square
Marlboro MA 01752 Ashburn, Va. 20147
tom.worster@gdc.com USA
Phone: (703) 724-2619
FAX: (703) 724-2005
liwen.wu@adn.alcatel.com
Jamoussi, et. al. February 25, 1999 [Page 29]
CR-LDP Specification - 30 - Exp. August 1999
Appendix A: CRLSP Establishment Examples
A.1 Strict 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 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 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 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.
2) There is a second ER-Hop, <b>. Go to step 3.
3) LSR2 is not part of the abstract node described by the second
ER-Hop <b>. Go to Step 4.
4) LSR2 determines that it is topologically adjacent to the
abstract node described by the second ER-Hop <b>. LSR2 selects a
next hop (LSR3) which is the abstract node. LSR2 deletes the first
ER-Hop <a> from the ER-TLV which now becomes <b , c>. 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
ER-TLV.
Also, LSR2 is not a member of the abstract node described by the
first ER-Hop <b>.
Finally, the first ER-Hop <b> 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
Jamoussi, et. al. February 25, 1999 [Page 30]
CR-LDP Specification - 31 - Exp. August 1999
already done is step 4 of Section 4.8.1 and the processing of the
ER-TLV is completed at LSR2. In this case, the Label Request
Message including the ER-TLV <b, c> is progressed by LSR2 to LSR3.
At LSR3, a similar processing to the ER-TLV takes place except that
the incoming ER-TLV = <b, c> and the outgoing 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 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 ER-TLV.
LSR4 does not add a new 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 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
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 explicit route and to create the Label
Request Message.
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The Label request message carries together with other necessary
information a ER-TLV defining the 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 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:
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.
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7. It sends a Label Request 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 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.
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Appendix B. QoS Service Examples
B.1 Service Examples
Construction of an end-to-end service is the result of the rules
enforced at the edge and the treatment that packets receive at the
network nodes. The rules define the traffic conditioning actions that
are implemented at the edge and they include policing with pass,
mark, and drop capabilities. The edge rules are expected to 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 network node is usually referred to as the
local behavior. Local behavior could be specified in many ways. One
example for local behavior specification is the service frequency
introduced in section 4.3.2.1., together with the resource
reservation rules implemented at the nodes.
Edge rules and local behaviors can be viewed as the main building
blocks for 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
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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 a 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 discarded.
The TS refers to a generic throughput sensitive service where the
network commit to deliver with high probability user datagrams at a
rate of at least CDR. The user may transmit at a rate higher than CDR
but datagrams in excess of CDR would have a lower probability of
being delivered.
The BE is the best effort service and it implies that there are 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 requested in this case.
The first step is the specification of the traffic parameters in the
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
assigned to all of them. For DS service, the CDR and the CBS values
are set equal to the PDR and the PBS respectively. An indication of
whether the parameter values are subject to negotiation is flagged.
The transport characteristics of the DS service requires that
Frequent frequency to be requested to reflect the real-time delay
requirements of the service.
In addition to the transport characteristics, both the network
provider and the customer need to agree on the actions enforced at
the edge. The specification of those actions is expected to be a part
of the service level agreement (SLA) negotiation and is 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 following the normal LDP procedures. Each
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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 the PDR, the PBS, or 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 example we assume that a throughput sensitive (TS) service is
requested. For resource allocation the 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 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 echoed back in the Label Mapping
Message. LSRs might need to re-adjust their resources based on the
new traffic parameter values.
