Network Working Group K. Shiomoto (NTT)
Internet Draft R. Rabbat (Google)
Updates: 3477, 4206 A. Ayyangar (Nuova Systems)
Proposed Category: Proposed Standard A. Farrel (Old Dog Consulting)
Z. Ali (Cisco Systems, Inc.)
Expires: October 2007 April 26, 2007
Procedures for Dynamically Signaled Hierarchical Label Switched Paths
draft-ietf-ccamp-lsp-hierarchy-bis-02.txt
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This Internet-Draft will expire on October 26, 2007.
Abstract
This document discusses topics related to hierarchical and stitched
Generalized Multiprotocol Label Switching (GMPLS) Label Switched
Paths (LSPs). It describes extensions to allow an egress to identify
that a bi-directional LSP will be used as a dynamically signaled
Forwarding Adjacency LSP (FA-LSP) or as a Routing Adjacency (RA). In
addition, the document also discusses the issue of how to indicate
that an LSP should be advertised as a traffic engineering (TE) link
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into a different instance of the IGP, and how to identify the
instance that should be used.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Table of Contents
1. Introduction and Problem Statement.............................3
1.1. LSP Hierarchy.............................................3
1.2. LSP advertisement and Usage...............................4
1.3. Problem Statement.........................................4
1.4. Current Approaches and Shortcomings.......................6
1.5. Contents of This Document.................................7
2. Changes from version draft-ietf-ccamp-lsp-hierarchy-bis-00.....7
3. Proposed Solution..............................................7
3.1. IGP Instance Identification...............................8
3.2. LSP advertisement and Usage Identification................9
3.3. Bundling..................................................9
3.4. LSP_TUNNEL_INTERFACE_ID Object...........................10
3.4.1. Unnumbered link.....................................10
3.4.2. IPv4 numbered link..................................11
3.4.3. IPv6 numbered link..................................12
3.4.4. Unnumbered link with target IGP instance identifier.13
3.4.5. Message Formats.....................................13
3.5. TLVs.....................................................14
3.5.1. Unnumbered Component Link Identifier................14
3.5.2. IPv4 Numbered Component Link Identifier.............15
3.6. LSA advertisement........................................15
4. Applicability Statement.......................................16
5. Backward Compatibility Considerations.........................16
6. Security Considerations.......................................16
7. IANA Considerations...........................................17
8. Acknowledgement...............................................17
9. References....................................................17
9.1. Normative References.....................................17
9.2. Informative References...................................17
Author's Addresses...............................................18
Intellectual Property Statement..................................18
Copyright Statement..............................................19
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1. Introduction and Problem Statement
1.1. LSP Hierarchy
LSP hierarchy has been developed to improve the scalability of
Generalized Multi-Protocol Label Switching (GMPLS) by allowing Label
Switched Paths (LSPs) to be aggregated into a hierarchy of such LSPs
[RFC4206]. An LSP may be advertised as a traffic engineering (TE)
link for use within the same instance of the control plane as was
used to set up the LSP. This TE link is called a Forwarding Adjacency
(FA), and the LSP is known as an FA-LSP.
[RFC4206] defines the operation as follows for a numbered FA:
1. The ingress signals the LSP using a /31 sender address that it
allocates as the source address in the signaling message (tunnel
sender address in the Sender Template object of the Path message),
and targeting the TE router ID of the egress (destination address
in the Sender object of the Path message).
2. The egress sets up the LSP using normal procedures and allocating
the partner address of the assigned /31 address in the local
interface address.
3. The ingress then forms a Forwarding Adjacency (FA) out of that LSP
by advertising it as a Traffic Engineering (TE) link using the
routing protocol (OSPF/ISIS) and using the /31 address to
identify the local end of the TE link.
4. When the egress receives the TE link advertisement, it checks the
Link-ID address of the TE advertisement against its own TE Router
ID. If it matches its own TE Router ID, the egress checks the
advertising router ID of the TE advertisement against the ingress
addresses of all LSPs for which it is the egress and finds the
address match with the advertising router ID of the TE
advertisement.
5. The egress then advertises the FA LSP as a TE link setting the
advertising TE Router ID in the Link-ID and the partner address of
the assigned /31 address in the local interface address.
Nesting of LSPs originated by other LSRs into that LSP can be
achieved by using the label stack construct.
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1.2. LSP advertisement and Usage
There are three different ways in which traffic can be forwarded to
an LSP. Similarly, the LSP can be advertised into the IP topology,
the MPLS TE topology or both, depending on the intended usage.
As GMPLS LSPs can be bidirectional, full routing adjacencies can be
established over a bidirectional GMPLS LSP. When an LSP is used as an
RA, it is advertised into IP network and can optionally be advertised
into the MPLS topology. The notion of RA is only applicable to
bidirectional LSPs.
As mentioned above, there is no IGP adjacency over the LSP, when it
is to be used as an FA. FA-LSPs can be advertised into the IP and/ or
MPLS topologies. Notion of FA is equally applicable to the
unidirectional as well as bidirectional LSPs.
There are also scenarios where intent of establishing an LSP is to
use it for traffic local to the Ingress/ Egress LSRs. In this case,
the LSP is neither advertised into the IP nor in MPLS topologies. In
this document, such LSPs are referred as local virtual links.
Forwarding treatment for a local virtual link is based on a local
decision.
1.3. Problem Statement
The extensions described in this document are intended for
dynamically signaled bi-directional Forwarding Adjacency LSPs (FA-
LSPs). In particular this document addresses the following points:
(1) How to let the egress node know that this bi-directional LSP
needs to be advertised as an FA, or as routing adjacency (RA),
or is only for the use of the ingress and egress nodes.
(2) How to indicate that a new LSP should be treated as part of a
TE link bundle and advertised as part of that bundle.
(3) How to identify the routing instance in which such an
advertisement should happen.
We should note that these aspects are equally applicable to both
numbered and unnumbered TE links.
In order for the egress of an LSP to be able to advertise the LSP as
a TE link it needs to know that such an advertisement is desirable,
and it also needs to know the TE Router ID of the ingress LSR.
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(Please recall that the Router ID of the other end of the link is set
in the Link-ID sub-TLV of the Link TLV of the TE Opaque-LSA
[RFC3630].) If the LSP is to form part of a TE link bundle, the
egress must also know the identity of the bundle.
When the mechanism set out in section 1.1 is used for numbered FAs,
there is no way to carry the TE Router ID of the ingress LSR in the
RSVP signaling message (Path message) and there is no way to indicate
that the new LSP is to be used as an FA LSP. Therefore the egress LSR
has to wait to receive a routing protocol advertisement of the TE
link flooded by the ingress to learn about the new TE link and to
deduce that the LSP forms that TE link. The egress must learn the TE
Router ID of the ingress node before it can advertise the FA as
described in Section 1.2. Note further, that in this approach, the
egress LSR must search potentially many LSPs every time it receives
an advertisement for a new TE link.
[RFC3477] defines a different method for the exchange of information
in the signaling protocol during the establishment of LSPs that will
be advertised as unnumbered TE links. If the LSP_TUNNEL_INTERFACE_ID
object is present, it indicates that the LSP is to be advertised as a
TE link, and it contains the TE Router ID of the ingress LSR. This
mechanism resolves many of the issues listed above, and provides a
solution for unnumbered TE links, however, the
LSP_TUNNEL_INTERFACE_ID object cannot be used for numbered FAs as
currently defined, and so the problem remains for numbered TE links.
Related to the above problem, a few key observations are worth
noting:
1. The term FA is applicable only when an LSP is created and used as
a TE link in the same instance of the IGP. [RFC4206] did not
consider scenarios where an LSP is created (and maintained) by one
instance of the IGP, and is used as a (TE) link by another
instance of IGP. This leaves open the question of advertising a TE
link into a different instance of the IGP as is needed in multi-
region/multi-layer networks [MLN], and how to identify which
instance of the IGP should be used. In addition, the TE link
advertised into the different IGP instance may be associated with
an IGP neighbor adjacency. We call it a routing adjacency (RA).
The decision as to whether the link should be advertised to MPLS
TE topology or IP topology or both depends on operator policy.
Therefore, a mechanism to indicate the choice to the Egress node
is needed.
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2. [RFC4206] provides a way to exchange numbered identifiers for the
TE link, but this does not clearly state that the Ingress node can
use presence of the LSP_TUNNEL_INTERFACE_ID object as a trigger
for TE link advertisement at the egress node.
3. It is important to note that an LSP that is set up in a server
GMPLS transport network and advertised as a TE link in a client
MPLS data network is NOT an FA-LSP according to the definitions
explained in point 1, above. This is the case regardless of
whether the GMPLS network is packet- or non-packet-capable.
4. When an egress checks the address of the advertised TE link to
find the LSP sender (Recall step (4) as described in section 1.1),
it must check the Link-ID address of all received TE
advertisements against its own TE Router ID. If it matches its
own TE Router ID, the egress checks the advertising router ID of
the TE advertisement against the ingress addresses of all LSPs for
which it is the egress. It is an assertion of the authors that
this method is not scalable due to the amount of processing needed
for all the TE Link State Advertisements (LSAs).
Further, if a set of LSPs are to be bundled into a single TE link
[RFC4201] then not only is it necessary to identify to the egress
that the LSP will be advertised as part of a TE link, it is also
necessary to indicate the identity of the TE link. This identity is
distinct from the identity of the component link. Thus, in this case
an additional identifier needs to be signaled, but none is currently
available.
1.4. Current Approaches and Shortcomings
[RFC3477] provides a mechanism to exchange unnumbered identifiers for
the TE link during FA-LSP establishment, and this can be used as a
notification to the egress that the LSP will be used as a TE link. So,
for unnumbered TE links, there is a well-defined indication available,
and this could be documented and used as a trigger for TE link
advertisement by the egress.
The use of unnumbered TE links may be arguably more sensible than
assigning numbers to FAs, especially in the case of large networks.
Some operators though prefer to consistently use numbered TE links
for both static and dynamic (that is, FA) TE links in their networks.
In the case of numbered TE links, however, there is no available
indication to allow the egress to know that an LSP should be
advertised as a TE link.
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In addition, using unnumbered TE links does not address the issue of
advertising TE links into a different instance of the IGP. There is
no defined mechanism to identify whether it should be advertised as
an FA, a full Routing Adjacency (RA), or a static link.
The Link Management Protocol (LMP) [RFC4204] could possibly be run on
remote adjacencies between the endpoints of an LSP. But LMP peer
discovery would be required for dynamic LMP peering and is not
currently specified. In addition, the concept of a remote LMP
adjacency remains unproven. Lastly, there would be a requirement
that all layers/regions in a MLN network run LMP. This may not be
the case in existing networks and would put undue burden on the
network operator to deploy another protocol.
1.5. Contents of This Document
This document provides a consolidated way of exchanging TE link
identifiers when an LSP is established through signaling. It also
provides a mechanism to allow the ingress to control whether, and
into which IGP instances, an LSP is advertised as an FA and/ or RA by
the egress. The proposed mechanism applies equally to Hierarchical
LSPs (H-LSPs) and Stitchable LSPs (S-LSPs).
The method described below extends the method described in [RFC3477],
which is applied for an FA-LSP represented as an unnumbered TE link.
2. Changes from version draft-ietf-ccamp-lsp-hierarchy-bis-00
o Fixed page formatting
o Updated author addresses
o Readability fixes
3. Proposed Solution
The following method allows the ingress and egress LSRs to exchange
the link addresses or link identifiers (including the node ID) of the
ends of a numbered or unnumbered TE link to be formed from an LSP.
It is an extension of the procedures defined in [RFC3477] for
unnumbered TE links.
If an Ingress LSR that originates an LSP, intends to advertise this
LSP as a TE link in IS-IS or OSPF [RFC4206], the Ingress LSR MUST
allocate an address or identifier to the TE link (just like for any
other TE link), and it MUST do this before the LSP setup request is
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signaled. Moreover, the Path message used for establishing the LSP
that will be used to form the TE link MUST contain the
LSP_TUNNEL_INTERFACE_ID object (as extended and described below),
with the interface address or identifier allocated by the Ingress LSR.
If the Path message for the H-LSP/S-LSP contains the
LSP_TUNNEL_INTERFACE_ID object, then the Egress LSR (assuming it
accepts the LSP request) MUST allocate an address or identifier to
the TE link that will be formed (just like for any other numbered or
unnumbered TE link). Furthermore, the Resv message for the LSP MUST
contain an LSP_TUNNEL_INTERFACE_ID object, with the interface address
or identifier allocated by the Egress LSR.
In all cases where an LSP is to be advertised as a TE link, the
Tunnel Sender Address in the Sender Template Object of the Path
message MUST be set to the TE Router ID of the Ingress LSR. We should
note that this is a change from the method described in [RFC4206].
Once the Egress LSR has successfully sent a Resv message as described
above it SHOULD advertise the LSP as a TE link using the
addresses/identifiers exchanged. Once the Resv has been processed by
the Ingress LSR and the LSP has been successfully established, the
Ingress LSR SHOULD advertise the LSP as a TE link using the
addresses/identifiers exchanged.
Once the TE link advertisement has been flooded it is available for
use in path computation and LSP signaling just like any other TE link.
3.1. IGP Instance Identification
The mechanism described so far allows an Ingress LSR to indicate that
an LSP is to be used as a TE link and allows the Ingress and Egress
LSRs to exchange addresses or identifiers for that TE link, during
LSP setup.
However, it is also necessary to indicate into which instance of the
IGP the advertisement should be made. This is only necessary if the
LSP is to be advertised as a TE link into a different instance of the
IGP, and the default behavior may safely be left with the LSP
advertised into the same instance of the IGP (that is, FA behavior).
Indication of the IGP in which the advertisement is to be made first
requires that a 32-bit identifier be assigned to each of the IGP
instances within a network, and that Ingress and Egress LSRs have the
same understanding of these numbers. This is a management
configuration exercise outside the scope of this document.
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Once these numbers have been assigned, they MAY be signaled as
additional information in the LSP_TUNNEL_INTERFACE_ID object to
indicate to which instance of the IGP the object applies.
The IGP instance identifier value of 0xffffffff is reserved to
indicate that the TE link SHOULD be advertised into the same instance
of the IGP as was used to establish the LSP. Similarly, absence of
the IGP instance identifier means that an FA is to be established (in
the same IGP instance).
3.2. LSP advertisement and Usage Identification
As mentioned earlier, the Egress node also needs to know if it needs
to create a full routing adjacency or forwarding adjacency or just
need to treat the LSP as a local virtual link. The extensions defined
in the following also specify the LSP advertisement and usage
treatment.
It is not mutually exclusive whether the LSP has routing adjacency
and whether it has forwarding adjacency. The LSP can have both
routing and forwarding adjacency. In this case, the LSP can be used
to carry both pure IP datagram packets and MPLS labeled packets. If
the LSP has only forwarding adjacency, it is used as TE-link to carry
only MPLS labeled packets. If the LSP has only routing adjacency, it
is used as IP link to carry only pure IP datagram packets.
It is mutually exclusive whether the LPS has routing adjacency and
whether it is treated as a local virtual link. Likewise, it is
mutually exclusive whether the LSP has forwarding adjacency and
whether it is treated as a local virtual link.
3.3. Bundling
It is possible to treat LSPs as component links and to bundle them
into a single TE link. However there is currently no way to signal
that an LSP will be used as part of a bundle and to identify the
bundled link to which the LSP is supposed to belong.
Each LSP that is to form a component link is signaled using the
LSP_TUNNEL_INTERFACE_ID object to identify the TE link bundle to
which the LSP will belong. Thus multiple LSPs may be signaled with
the same address/identifier in the LSP_TUNNEL_INTERFACE_ID object.
When the LSP is to form a component link, the LSP_TUNNEL_INTERFACE_ID
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object MUST also contain an additional TLV to identify the component
link. This may be a numbered or unnumbered identifier.
Multiple LSPs may be signaled with the same address/identifier in the
LSP_TUNNEL_INTERFACE_ID object.
3.4. LSP_TUNNEL_INTERFACE_ID Object
The LSP_TUNNEL_INTERFACE_ID object defined in [RFC3477] has a class
number of 193, which designates that a node that does not understand
the object SHOULD ignore the object but forward it, unexamined and
unmodified, in all messages resulting from this message.
[RFC3477] defines one class type to indicate an unnumbered interface
identifier. This document defines three new class types as follows.
C-Type Meaning Reference
---------------------------------------------------------------------
1 Unnumbered interface identifier [RFC3477]
2 (TBD by IANA) IPv4 interface identifier with target 2.2.2
3 (TBD by IANA) IPv6 interface identifier with target 2.2.3
4 (TBD by IANA) Unnumbered interface with target 2.2.4
Multiple instances of the LSP_TUNNEL_INTERFACE_ID object with C-Type
values 2, 3 or 4 MAY appear in any one Path or Resv message, in which
case, each MUST have a different value for the Target IGP Instance
field. A Path or Resv message MUST NOT contain more than one
instance of the LSP_TUNNEL_INTERFACE_ID object with C-Type 1, and if
such an object is present, other instances of the object with any
other C-Type value MUST NOT have Target IGP Instance set to
0xffffffff.
3.4.1. Unnumbered link
The unnumbered link identifier defined by [RFC3477] is not changed by
this document. Its usage also remains the same. That is, when
present in a Path message it indicates that the LSP being established
SHOULD be advertised by the egress LSR as a TE link, and that
unnumbered link identifier is the ingress' identifier for the TE link.
Note that since this form of the object does not contain a target IGP
instance identifier it cannot identify a specific instance of the IGP
into which this TE link should be advertised. Similarly, LSP
advertisement and usage treatment also needs to be specified. Thus,
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when C-Type 1 is used, the TE link SHOULD be advertised only into the
same instance of the IGP as was used to create the LSP. That is, the
use of C-Type 1 is unchanged from [RFC3477] and is used to create an
unnumbered Forwarding Adjacency.
This object can appear in either a Path message or a Resv message.
In the former case, we call it the "Forward Interface ID" for that
LSP; in the latter case, we call it the "Reverse Interface ID" for
the LSP.
A Path or Resv message MUST have only one instance of this object
with C-Type 1.
3.4.2. IPv4 numbered link
A new C-Type variant of the LSP_TUNNEL_INTERFACE_ID Object is defined
to carry an IPv4 numbered interface address and to indicate into
which instance of the IGP the consequent TE link should be advertised.
The format of the object is as shown below.
C-NUM = 193, C-Type = 2(TBD by IANA)
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Interface Address (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target IGP Instance (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ACTION | PADDING |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLVs |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ACTION: This field specifies how the LSP advertisement and usage
treatment. It indicates if the egress LSR needs to create a full
routing adjacency or forwarding adjacency or just need to treat the
LSP as a local virtual link. It takes the following values:
"0000": LSP is an FA and is only advertised into the MPLS-TE topology.
We should note that it assures the backward compatibility with the
method to exchange unnumbered FA information described in [RFC3477].
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"0001": LSP is an RA and is only advertised into the IP network.
"0010": LSP is an RA and is advertised in both IP and MPLS-TE
topologies.
"0011": LSP is neither the FA nor RA and is to be used as a local
virtual link. In this case the LSP is advertised neither in IP nor
MPLS topology.
The Padding MUST be set to zero on transmission, SHOULD be ignored
and forwarded unchanged, and SHOULD be ignored on receipt.
This object can appear in either a Path message or a Resv message.
In the former case, we call it the "Forward Interface Address" for
that LSP; in the latter case, we call it the "Reverse Interface
Address" for the LSP.
3.4.3. IPv6 numbered link
A new C-Type variant of the LSP_TUNNEL_INTERFACE_ID Object is defined
to carry an IPv6 numbered interface address and to indicate into
which instance of the IGP the consequent TE link should be advertised.
The format of the object is as shown below.
C-NUM = 193, C-Type = 3(TBD by IANA)
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Interface Address (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Interface Address (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Interface Address (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Interface Address (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target IGP Instance (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ACTION | PADDING |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLVs |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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This object can optionally appear in either a Path message or a Resv
message. In the former case, we call it the "Forward Interface
Address" for that LSP; in the latter case, we call it the "Reverse
Interface Address" for the LSP.
3.4.4. Unnumbered link with target IGP instance identifier
A new C-Type variant of the LSP_TUNNEL_INTERFACE_ID Object is defined
to carry an unnumbered interface identifier and to indicate into
which instance of the IGP the consequent TE link should be advertised.
This does not deprecate the use of C-Type 1, but extends its utility.
The format of the object is as shown below.
C-NUM = 193, C-Type = 4(TBD by IANA)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSR's Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target IGP Instance (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ACTION | PADDING |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLVs |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This object can optionally appear in either a Path message or a Resv
message. In the former case, we call it the "Forward Interface ID"
for that LSP; in the latter case, we call it the "Reverse Interface
ID" for the LSP.
3.4.5. Message Formats
[RFC3477] does not state where in the Path message or Resv message
the LSP_TUNNEL_INTERFACE_ID object should be placed. Since [RFC3209]
states that all implementations are to handle all objects received in
any order, this is not a problem. However, it is RECOMMENDED that the
LSP_TUNNEL_INTERFACE_ID object(s) be placed in the Path message
immediately after the SENDER_TSPEC object, and in the Resv message
immediately after the FILTER_SPEC object.
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3.5. TLVs
All TLVs of the LSP_TUNNEL_INTERFACE_ID object have the following
format.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (16 bits) | Length (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (variable) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The length field contains the total length of the TLV including the
Type and Length fields in bytes A value field whose length is not a
multiple of four MUST be zero-padded so that the TLV is four-byte
aligned.
This document defines two Type values to be used to specify the
component link identifier that the sending LSR has assigned to the
LSP if it forms part of a TE link bundle. The consequent TLV formats
are shown in the next sections.
3.5.1. Unnumbered Component Link Identifier
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 1 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Component Link Identifier (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This TLV is present if the signaled LSP is to be used as an
unnumbered component link of a bundled TE link. In this case, the
identifier (numbered or unnumbered) in the main body of the
LSP_TUNNEL_INTERFACE_ID object indicates the TE link bundle of which
this LSP is a component, and the Component Link Identifier of this
TLV specifies the unnumbered identifier that is assigned to this
component link within the bundle.
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This TLV MUST NOT be present in the same instance of the
LSP_TUNNEL_INTERFACE_ID object as a TLV with type 2 (numbered
component link identifier).
3.5.2. IPv4 Numbered Component Link Identifier
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 2 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This TLV is present if the signaled LSP is to be used as a numbered
component link of a bundled TE link. In this case, the identifier
(numbered or unnumbered) in the main body of the
LSP_TUNNEL_INTERFACE_ID object indicates the TE link bundle of which
this LSP is a component, and the IPv4 Address field of this TLV
specifies the numbered identifier that is assigned to this component
link within the bundle.
This TLV MUST NOT be present in the same instance of the
LSP_TUNNEL_INTERFACE_ID object as a TLV with type 1 (unnumbered
component link identifier).
3.6. LSA advertisement
The ingress and egress LSRs MAY advertise link state associated with
TE links created as described above. The link state may be
advertised in either the same IGP instance as used to compute and
signal the path for the LSPs that support the TE links, or another
IGP instance. In the former case, the address space for the link
state MUST be the same as that used to establish the LSPs. In the
latter case, the address space for the link state MAY be different,
which means that addresses already allocated in the IGP instance used
to establish the LSPs MAY be used by the advertised TE link without
any ambiguity.
In the IGP the TE Router ID of the ingress LSR is taken from the
Tunnel Sender Address in the Sender Template object. It is assumed
that the ingress LSR knows the TE Router ID of the egress LSR since
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it has chosen to establish an LSP to that LSR and plans to use the
LSP as a TE link.
The link interface addresses or link interface identifiers for the
forward and reverse direction links are taken from the
LSP_TUNNEL_INTREFACE_ID object on the Path and Resv messages
respectively.
Address overlap checking for these objects MUST be turned off when
the LSA is advertised into a IGP instance different from the one used
to establish the LSP because the addresses MAY be allocated in both
domains.
4. Applicability Statement
The method is applicable for both hierarchical LSPs [RFC4206] and LSP
stitching [STITCH].
5. Backward Compatibility Considerations
The method does not impact the method to exchange unnumbered FA
information described in [RFC3477]. That mechanism can be safely
used in combination with the new mechanisms described here and is
functionally equivalent to using the new C-Type indicating an
unnumbered link with target IGP instance identifier with the Target
IGP Instance value set to 0xffffffff.
This method obsoletes the method to exchange the numbered FA
information described in [RFC4206]. This is not believed to be an
issue as an informal survey indicated that dynamically signaled
numbered FAs had not been deployed. Indeed it was the attempt to
implement numbered FAs that gave rise to the work on this document.
6. Security Considerations
[RFC3477] points out that one can argue that the use of the extra
interface identifier that it provides could make an RSVP message
harder to spoof. In that respect, the minor extensions to the
protocol made in this document do not constitute an additional
security risk, but could also be said to improve security.
It should be noted that the ability of an ingress LSR to request that
an egress LSR advertise an LSP as a TE link MUST be subject to
appropriate policy checks at the egress LSR. That is, the egress LSR
MUST NOT automatically accept the word of the ingress unless it is
configured with such a policy.
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7. IANA Considerations
This document defines three new C-Types for the
LSP_TUNNEL_INTERFACE_ID object. The C-Types for this object are
managed by IANA, and IANA is requested to assign values to the new C-
Types as tabulated in section 2.2 and described in sections 2.2.2,
2.2.3 and 2.2.4.
8. Acknowledgement
The authors would like to thank John Drake and Yakov Rekhter for
their valuable discussions and comments.
Funding for the RFC Editor function is currently provided by the
Internet Society.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3477] Kompella, K. and Rekhter, Y., "Signalling Unnumbered Links
in Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", RFC 3477, January 2003.
[RFC4201] Kompella, K., Rekhter, Y., and Berger, L.," Link Bundling
in MPLS Traffic Engineering (TE)", RFC 4201, October 2005.
[RFC4206] Kompella, K. and Y. Rekhter, "LSP Hierarchy with
Generalized MPLS TE", RFC 4206, October 2005.
[STITCH] Ayyangar, A. and J.P. Vasseur, "Label Switched Path
Stitching with Generalized MPLS Traffic Engineering",
draft-ietf-ccamp-lsp-stitching, (work in progress).
9.2. Informative References
[RFC3630] Katz, D., Kompella, K. and Yeung, D., "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
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[RFC4204] Lang, J. (Ed.), "Link Management Protocol (LMP)", RFC
4204, October 2005.
[MLN] Shiomoto, K., et al, " Requirements for GMPLS-based multi-
region and multi-layer networks (MRN/MLN)", draft-ietf-
ccamp-gmpls-mln-reqs, (work in progress).
Author's Addresses
Kohei Shiomoto
NTT Network Service Systems Laboratories
3-9-11 Midori
Musashino, Tokyo 180-8585
Japan
Phone: +81 422 59 4402
Email: shiomoto.kohei@lab.ntt.co.jp
Richard Rabbat
Google Inc.
Email: rabbat@alum.mit.edu
Arthi Ayyangar
Nuova Systems
2600 San Tomas Expressway
Santa Clara, CA 95051
Email: arthi@nuovasystems.com
Adrian Farrel
Old Dog Consulting
EMail: adrian@olddog.co.uk
Zafar Ali
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario, K2K 3E8
Canada.
EMail: zali@cisco.com
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