Network Working Group K. Shiomoto (NTT)
Internet Draft R. Rabbat (Google)
Updates: 3477, 4206 A. Ayyangar (Juniper Networks)
Proposed Category: Proposed Standard A. Farrel (Old Dog Consulting)
Z. Ali (Cisco Systems, Inc.)
Expires: August 2008 February 22, 2008
Procedures for Dynamically Signaled
Hierarchical Label Switched Paths
draft-ietf-ccamp-lsp-hierarchy-bis-03.txt
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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
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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 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........................................6
1.4. Current Approaches and Shortcomings.......................8
1.5. Contents of This Document.................................9
2. Revision history...........................................9
2.1. Changes from version draft-ietf-ccamp-lsp-hierarchy-bis-00.9
2.2. Changes from version draft-ietf-ccamp-lsp-hierarchy-bis-01.9
2.3. Changes from version draft-ietf-ccamp-lsp-hierarchy-bis-02.10
3. Proposed Solution..........................................10
3.1. IGP Instance Identification...............................11
3.2. LSP advertisement and Usage Identification................11
3.3. Bundling.................................................12
3.4. LSP_TUNNEL_INTERFACE_ID Object............................12
3.4.1. Unnumbered link.........................................13
3.4.2. IPv4 numbered link......................................14
3.4.3. IPv6 numbered link......................................15
3.4.4. Unnumbered link with target IGP instance identifier......16
3.4.5. Message Formats........................................16
3.5. TLVs.....................................................17
3.5.1. Unnumbered Component Link Identifier....................17
3.5.2. IPv4 Numbered Component Link Identifier.................18
3.6. LSA advertisement........................................18
4. Applicability Statement.....................................19
5. Backward Compatibility Considerations.......................19
6. Security Considerations.....................................19
7. IANA Considerations........................................20
8. Acknowledgement............................................20
9. References.................................................20
9.1. Normative References.....................................20
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9.2. Informative References....................................20
Author's Addresses............................................21
Intellectual Property Statement................................22
Copyright Statement...........................................23
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.
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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.
1.2. LSP advertisement and Usage
There are three different ways in which traffic can be forwarded
to
There are different ways in which an LSP can be used to carry
traffic and potentially advertised as a link by a routing
protocol.
First, the LSP can be used either as a link inside or outside
the network that was used to form the LSP. In the former case,
the LSP can carry traffic that could have been routed down the
TE links that are navigated by the LSP. In the latter case, it
is used by a client network, which is provided on top of the
network [MLN-REQ]. It can provide a new, virtual, point-to-point
link in a client network. The former case can only be achieved
in packet networks as they are the only type of network that
supports nesting of LSPs within the same technology LSP, but the
latter case is applicable to all client/server network
relationships such as IP over MPLS, or packet over optical.
Second, the link formed by the LSP can be advertised by the
routing protocol as available to carry traffic, or can be kept
as a private link known only to the head and tail end LSRs.
These two options give rise to four possible combinations as
follows.
1. The LSP is created and advertised as a TE link in the same
instance of the routing protocol as was used to advertise the
links that it traverses. This is a Forwarding Adjacency as
described in [RFC4206]. Note that no routing adjacency is formed
over the LSP.
2. The LSP is created and made available to carry traffic in the
same network as the links that it traverses, but it is not
advertised. The availability of the LSP is private to the end
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points. This is a hierarchical LSP, but not an FA. It might be
used for inter-domain traffic engineering [RFC4726].
3. The LSP is created as before, but is advertised as a link in
another instance of the routing protocol. This method of
operation is particular to client/server networks and especially
multi-layer networks [MLN-REQ], [PCE-INTER-LAYER-REQ].
4. An LSP can be created and used by a client network without
being advertised in the client network routing protocol. Just as
in case 2, the existence of the LSP as a protocol tunnel is
known only to the tunnel LSP points which are nodes in the
client network.
Notes:
a. Case 1 includes the multi-layer traffic engineering scenario
where a single instance of the routing protocol is used across
both layers. This situation was particularly envisaged in
[RFC4206].
b. The example cited in case 2 is special because the
hierarchical LSP is edge-to-edge within a particular domain and
no TE links are advertised outside of the domain (by definition
of the domain). The purpose of the TE link is to carry traffic
across the domain and not to carry intra-domain traffic.
Advertising the TE link within the domain might cause internal
traffic to take longer paths as it seeks to use the hierarchical
LSP.
c. Case 3 is not the only option for the multi-layer network as
explained in Note a.
d. The client network in case 3 may be a different technology TE
network (such as a GMPLS TDM network that operates over a GMPLS
WDM network, or an MPLS-TE network operating over a GMPLS
optical network), a same-technology TE network where LSP nesting
is allowed (for example, an MPLS-TE network operating over
another MPLS-TE network), or a non-TE network (such as an IP
network operating over an MPLS-TE or GMPLS network of any
technology). Thus, the link advertised may be a TE link, or a
routing link. In the second instance, the LSP is used to form a
virtual adjacency between two non-neighboring IP routers (a
Routing Adjacency - RA) forming IGP shortcuts.
e. IGP shortcuts are precluded when the LSP end-points reside
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within different IGP areas [RFC4105].
f. IGP shortcuts should be treated with extreme caution when
they are created and used in the same IP/MPLS network. Thus, it
may be more common to use them as described in case 4 and even
in this case, only when the egress of the LSP is the final
destination of the traffic carried.
g. It would be unusual although not impossible to use a
hierarchical LSP as an IGP shortcut within the control plane.
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 an RA, or as an
FA and RA or is a local virtual link 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. (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
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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:
6. 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-REQ],
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.
7. [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.
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8. 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.
9. 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).
10.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.
In addition, using unnumbered TE links does not address the
issue of advertising TE links into a different instance of the
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IGP. There is no defined mechanism to identify whether it should
be advertised as an FA, a full Routing Adjacency (RA), or it
should be used as a local virtual 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. Revision history
2.1. Changes from version draft-ietf-ccamp-lsp-hierarchy-bis-00
o Fixed page formatting
o Updated author addresses
o Readability fixes
2.2. Changes from version draft-ietf-ccamp-lsp-hierarchy-bis-01
o Added indication of bundled link
o Added "ACTION" field, which obsoletes R and F bits
o Readability fixes
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2.3. Changes from version draft-ietf-ccamp-lsp-hierarchy-bis-02
o Rewrite Section 1.2
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 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.
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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.
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.
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.
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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.
Note that the LSP which has only forwarding adjacency is useful
to improve the scalability. Suppose that distant PSC domains are
connected by a set of lower-layer LSPs created in the optical
domain (TDM, LSC, or FSC). We do not require routing adjacency on
all such lower-layer LSPs as long as we have control plane
connectivity through a subset of lower-layer LSPs which have
routing adjacency. We reduce the amount of overhead of IGP
protocol processing on the LSPs which do not have routing
adjacency.
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 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
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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, 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
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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 FA 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 |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This object can optionally appear in either a Path message or a
Resv message. In the former case, we call it the "Forward
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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 it has chosen to establish an LSP to that LSR
and plans to use the LSP as a TE link.
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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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[RFC4105]Le Roux, J.-L., Vassuer, J.-P., and Boyle, J. (Eds.),
"Requirements for Inter-Area MPLS Traffic Engineering",
RFC 4105, June 2005.
[RFC4204]Lang, J. (Ed.), "Link Management Protocol (LMP)",
RFC 4204, October 2005.
[RFC4726]Farrel, A., Vasseur, J.-P., and Ayyangar, A., " A
Framework for Inter-Domain Multiprotocol Label
Switching Traffic Engineering ", RFC 4726, November
2006.
[MLN-REQ]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).
[PCE-INTER-LAYER-REQ] Oki, E. (Ed.), " PCC-PCE Communication
and PCE Discovery Requirements for Inter-Layer Traffic
Engineering ", draft-ietf-pce-inter-layer-req, (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
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Richard Rabbat
Google Inc.
Email: rabbat@alum.mit.edu
Arthi Ayyangar
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
United States of America
Phone:
Email: arthi@juniper.net
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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