draft-ietf-ccamp-ospf-interas-te-extension-01.txt   draft-ietf-ccamp-ospf-interas-te-extension-02.txt 
Network work group Mach Chen Network work group Mach Chen
Internet Draft Renhai Zhang Internet Draft Renhai Zhang
Expires: March 2008 Huawei Technologies Co.,Ltd Expires: May 2008 Huawei Technologies Co.,Ltd
Category: Standards Track September 6, 2007 Category: Standards Track Xiaodong Duan
China Mobile
November 19, 2007
OSPF Traffic Engineering (OSPF-TE) Extensions in Support of Inter-AS OSPF Extensions in Support of Inter-AS Multiprotocol Label Switching
Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering
Traffic Engineering draft-ietf-ccamp-ospf-interas-te-extension-02.txt
draft-ietf-ccamp-ospf-interas-te-extension-01.txt
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Abstract Abstract
This document describes extensions to the OSPF v2 and v3 Traffic This document describes extensions to the OSPF version 2 and 3
Engineering (OSPF-TE) mechanisms to support Multiprotocol Label protocols to support Multiprotocol Label Switching (MPLS) and
Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering(TE) Generalized MPLS (GMPLS) Traffic Engineering(TE) for multiple
for multiple Autonomous Systems (ASes). It defines OSPF-TE extensions Autonomous Systems (ASes). OSPF-TE v2 and v3 extensions are defined
for the flooding of TE information about inter-AS links which can be for the flooding of TE information about inter-AS links which can be
used to perform inter-AS TE path computation. used to perform inter-AS TE path computation.
No support for flooding TE information from other outside the AS is
proposed or defined in this document.
Conventions used in this document Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119]. document are to be interpreted as described in RFC-2119 [RFC2119].
Table of Contents Table of Contents
1. Introduction.................................................2 1. Introduction.................................................2
2. Problem Statement............................................3 2. Problem Statement............................................3
2.1. A Note on Non-Objectives................................3 2.1. A Note on Non-Objectives................................4
2.2. Per-Domain Path Determination...........................4 2.2. Per-Domain Path Determination...........................4
2.3. Backward Recursive Path Computation.....................6 2.3. Backward Recursive Path Computation.....................6
3. Extensions to OSPF-TE........................................7 3. Extensions to OSPF...........................................7
3.1. Remote AS Number Sub-TLV................................7 3.1. LSA Definitions.........................................8
3.2. Inter-AS Link Type......................................8 3.1.1. Inter-AS-TE-v2 LSA.................................8
3.3. Link ID.................................................8 3.1.2. Inter-AS-TE-v3 LSA.................................8
4. Procedure for Inter-AS TE Links..............................8 3.2. LSA Payload.............................................9
5. Security Considerations......................................9 3.2.1. Link TLV...........................................9
6. IANA Considerations.........................................10 3.3. Sub-TLV Detail.........................................10
6.1. OSPF LSA Sub-TLVs type.................................10 3.3.1. Remote AS Number Sub-TLV..........................10
6.2. OSPF TE Link Type......................................10 3.3.2. IPv4 Remote ASBR ID Sub-TLV.......................11
7. Acknowledgments.............................................10 3.3.3. IPv6 Remote ASBR ID Sub-TLV.......................11
8. References..................................................11 4. Procedure for Inter-AS TE Links.............................12
8.1. Normative References...................................11 4.1. Origin of Proxied TE Information.......................13
8.2. Informative References.................................11 5. Security Considerations.....................................14
Authors' Addresses.............................................12 6. IANA Considerations.........................................14
Intellectual Property Statement................................12 6.1. Inter-AS TE OSPF LSA...................................14
Disclaimer of Validity.........................................13 6.2. OSPF LSA Sub-TLVs type.................................15
Copyright Statement............................................13 7. Acknowledgments.............................................15
8. References..................................................15
8.1. Normative References...................................15
8.2. Informative References.................................16
Authors' Addresses.............................................17
Intellectual Property Statement................................17
Disclaimer of Validity.........................................18
Copyright Statement............................................18
1. Introduction 1. Introduction
[OSPF-TE] defines extensions to the OSPF protocol [OSPF] to support [OSPF-TE] defines extensions to the OSPF protocol [OSPF] to support
intra-area Traffic Engineering (TE). The extensions provide a way of intra-area Traffic Engineering (TE). The extensions provide a way of
encoding the TE information for TE-enabled links within the network encoding the TE information for TE-enabled links within the network
(TE links) and flooding this information within an area. Type 10 (TE links) and flooding this information within an area. Type 10
opaque LSAs [RFC2370] are used to carry such TE information. Two top- opaque LSAs [RFC2370] are used to carry such TE information. Two top-
level TLVs are defined in [OSPF-TE]: Router Address TLV and Link TLV. level TLVs are defined in [OSPF-TE]: Router Address TLV and Link TLV.
The Link TLV has several nested sub-TLVs which describe the TE The Link TLV has several nested sub-TLVs which describe the TE
attributes for a TE link. attributes for a TE link.
[OSPF-TE-V3] defines similar extensions to OSPFv3 [OSPFV3]. [OSPF-V3-TE] defines similar extensions to OSPFv3 [OSPFV3]. It
defines a new LSA, which is referred to as the Intra-Area-TE LSA, to
advertise TE information. [OSPF-V3-TE] uses "Traffic Engineering
Extensions to OSPF" [OSPF-TE] as a base for TLV definitions and
defines some new TLVs and sub-TLVs to extend TE capabilities to IPv6
networks.
Requirements for establishing Multiprotocol Label Switching (MPLS) TE Requirements for establishing Multiprotocol Label Switching Traffic
Label Switched Paths (LSPs) that cross multiple Autonomous Systems Engineering (MPLS-TE) Label Switched Paths (LSPs) that cross multiple
(ASes) are described in [INTER-AS-TE-REQ]. As described in [INTER-AS- Autonomous Systems (ASes) are described in [INTER-AS-TE-REQ]. As
TE-REQ], a method SHOULD provide the ability to compute a path described in [INTER-AS-TE-REQ], a method SHOULD provide the ability
spanning multiple ASes. So a path computation entity that may be the to compute a path spanning multiple ASes. So a path computation
head-end Label Switching Router (LSR), an AS Border Router (ASBR), or entity that may be the head-end Label Switching Router (LSR), an AS
a Path Computation Element (PCE [PCE]) needs to know the TE Border Router (ASBR), or a Path Computation Element (PCE [PCE]) needs
information not only of the links within an AS, but also of the links to know the TE information not only of the links within an AS, but
that connect to other ASes. also of the links that connect to other ASes.
In this document, some extensions to OSPF-TE are defined in support In this document, two new separate LSAs are defined to advertise
of carrying inter-AS TE link information for inter-AS Traffic inter-AS TE information for OSPFv2 and OSPFv3 respectively, and three
Engineering. A new sub-TLV is added to the Link TLV and a new link new sub-TLVs are added to the existing Link TLV to extend TE
type is introduced. The extensions are equally applicable to OSPFv2 capabilities for inter-AS Traffic Engineering. The detailed
and OSPFv3 as identical extensions to [OSPF-TE] and [OSPF-TE-V3]. The definitions and procedures are discussed in the following sections.
detailed definitions and procedures are discussed in the following
sections. This document does not propose or define any mechanisms to advertise
any other extra-AS TE information within OSPF. See Section 2.1 for a
full list of non-objectives for this work.
2. Problem Statement 2. Problem Statement
As described in [INTER-AS-TE-REQ], in the case of establishing an As described in [INTER-AS-TE-REQ], in the case of establishing an
inter-AS TE LSP traversing multiple ASes, the Path message [RFC3209] inter-AS TE LSP traversing multiple ASes, the Path message [RFC3209]
may include the following elements in the Explicit Route Object (ERO) may include the following elements in the Explicit Route Object (ERO)
in order to describe the path of the LSP: in order to describe the path of the LSP:
- a set of AS numbers as loose hops; and/or - a set of AS numbers as loose hops; and/or
- a set of LSRs including ASBRs as loose hops. - a set of LSRs including ASBRs as loose hops.
Two methods for determining inter-AS paths are currently discussed. Two methods for determining inter-AS paths are currently being
The per-domain method [PD-PATH] determines the path one domain at a discussed. The per-domain method [PD-PATH] determines the path one
time. The backward recursive method [BRPC] uses cooperation between domain at a time. The backward recursive method [BRPC] uses
PCEs to determine an optimum inter-domain path. The sections that cooperation between PCEs to determine an optimum inter-domain path.
follow examine how inter-AS TE link information could be useful in The sections that follow examine how inter-AS TE link information
both cases. could be useful in both cases.
2.1. A Note on Non-Objectives 2.1. A Note on Non-Objectives
It is important to note that this document does not make any change It is important to note that this document does not make any change
to the confidentiality and scaling assumptions surrounding the use of to the confidentiality and scaling assumptions surrounding the use of
ASes in the Internet. In particular, this document is conformant to ASes in the Internet. In particular, this document is conformant to
the requirements set out in [INTER-AS-TE-REQ]. the requirements set out in [INTER-AS-TE-REQ].
The following lists of features are explicit exclusions. The following features are explicitly excluded.:
o There is no attempt to distribute TE information from within one o There is no attempt to distribute TE information from within one
AS to another AS. AS to another AS.
o There is no mechanism proposed to distribute any form of TE o There is no mechanism proposed to distribute any form of TE
reachability information for destinations outside the AS. reachability information for destinations outside the AS.
o There is no proposed change to the PCE architecture or usage. o There is no proposed change to the PCE architecture or usage.
o TE aggregation is not supported or recommended. o TE aggregation is not supported or recommended.
o There is no exchange of private information between ASes. o There is no exchange of private information between ASes.
o No OSPF adjacencies are formed on the inter-AS link. o No OSPF adjacencies are formed on the inter-AS link.
Note further that the extensions proposed in this document are Note also that the extensions proposed in this document are used only
limited to use for information about inter-AS TE links. L1VPN Auto- to advertise information about inter-AS TE links. As such these
Discovery [L1VPN-OSPF-AD] defines how TE information about links extensions address an entirely different problem from L1VPN Auto-
between Customer Edge (CE) equipment and Provider Edge (PE) equipment Discovery [L1VPN-OSPF-AD] which defines how TE information about
can be advertised in OSPF-TE alongside the auto-discovery information links between Customer Edge (CE) equipment and Provider Edge (PE)
for the CE-PE links. That is separate functionality and does not equipment can be advertised in OSPF-TE alongside the auto-discovery
overlap with the function defined in this document. information for the CE-PE links. There is no overlap between this
document and [L1VPN-OSPF-AD].
2.2. Per-Domain Path Determination 2.2. Per-Domain Path Determination
In the per-domain method of determining an inter-AS path for an MPLS- In the per-domain method of determining an inter-AS path for an MPLS-
TE LSP, when an LSR that is an entry-point to an AS receives a PATH TE LSP, when an LSR that is an entry-point to an AS receives a PATH
message from an upstream AS with an ERO containing a next hop that is message from an upstream AS with an ERO containing a next hop that is
an AS number, it needs to find which LSRs (ASBRs) within the local AS an AS number, it needs to find which LSRs (ASBRs) within the local AS
are connected to the downstream AS so that it can compute a TE LSP are connected to the downstream AS so that it can compute a TE LSP
segment across the AS to one of those LSRs and forward the PATH segment across the local AS to one of those LSRs and forward the PATH
message to the LSR and hence into the next AS. See the figure below message to it and hence into the next AS. See Figure 1 for an
for an example: example :
R1------R3----R5-----R7------R9-----R11 R1------R3----R5-----R7------R9-----R11
| | \ | / | | | \ | / |
| | \ | ---- | | | \ | ---- |
| | \ | / | | | \ | / |
R2------R4----R6 --R8------R10----R12 R2------R4----R6 --R8------R10----R12
: : : :
<-- AS1 -->:<---- AS2 --->:<--- AS3 ---> <-- AS1 -->:<---- AS2 --->:<--- AS3 --->
Figure 1: Inter-AS Reference Model Figure 1: Inter-AS Reference Model
The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1
through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are
ASBRs in AS2. R9 and R10 are ASBRs in AS3. ASBRs in AS2. R9 and R10 are ASBRs in AS3.
If an inter-AS TE LSP is planned to be established from R1 to R12, If an inter-AS TE LSP is planned to be established from R1 to R12,
the AS sequence is limited as: AS1, AS2, AS3. the AS sequence will be: AS1, AS2, AS3.
Suppose that the Path message enters AS2 from R3. The next hop in the Suppose that the Path message enters AS2 from R3. The next hop in the
ERO shows AS3, and R5 must determine a path segment across AS2 to ERO shows AS3, and R5 must determine a path segment across AS2 to
reach AS3. It has a choice of three exit points from AS2 (R6, R7, and reach AS3. It has a choice of three exit points from AS2 (R6, R7, and
R8) and it needs to know which of these provide TE connectivity to R8) and it needs to know which of these provide TE connectivity to
AS3, and whether the TE connectivity (for example, available AS3, and whether the TE connectivity (for example, available
bandwidth) is adequate for the requested LSP. bandwidth) is adequate for the requested LSP.
Alternatively, if the next hop in the ERO is the entry ASBR for AS3 Alternatively, if the next hop in the ERO is the entry ASBR for AS3
(say R9), R5 needs to know which of its exit ASBRs has a TE link that (say R9), R5 needs to know which of its exit ASBRs has a TE link that
connects to R9. Since there may be multiple exist ASBRs that are connects to R9. Since there may be multiple ASBRs that are connected
connected to R9 (both R7 and R8 in this example), R5 also needs to to R9 (both R7 and R8 in this example), R5 also needs to know the TE
know the TE properties of the inter-AS TE links so that it can select properties of the inter-AS TE links so that it can select the correct
the correct exit ASBR. exit ASBR.
Once the path message reaches the exit ASBR, any choice of inter-AS Once the path message reaches the exit ASBR, any choice of inter-AS
TE link can be made by the ASBR if not already made by entry ASBR TE link can be made by the ASBR if not already made by entry ASBR
that computed the segment. that computed the segment.
More details can be found in the Section 4.0 of [PD-PATH], which More details can be found in the Section 4.0 of [PD-PATH], which
clearly points out why advertising of inter-AS links is desired. clearly points out why advertising of inter-AS links is desired.
To enable R5 to make the correct choice of exit ASBR the following To enable R5 to make the correct choice of exit ASBR the following
information is needed: information is needed:
skipping to change at page 6, line 46 skipping to change at page 7, line 23
: : : :
<-- AS1 -->:<---- AS2 --->:<--- AS3 ---> <-- AS1 -->:<---- AS2 --->:<--- AS3 --->
Figure 2: BRPC for Inter-AS Reference Model Figure 2: BRPC for Inter-AS Reference Model
The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1, The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1,
PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are
ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are
ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS path ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS path
computation and are responsible for path segment computation within computation and are responsible for path segment computation within
their own domains. their own domain(s).
If an inter-AS TE LSP is planned to be established from R1 to R12, If an inter-AS TE LSP is planned to be established from R1 to R12,
the traversed domains are assumed to be selected: AS1->AS2->AS3, and the traversed domains are assumed to be selected: AS1->AS2->AS3, and
the PCE chain is: PCE1->PCE2->PCE3. First, the path computation the PCE chain is: PCE1->PCE2->PCE3. First, the path computation
request originated from the PCC (R1) is relayed by PCE1 and PCE2 request originated from the PCC (R1) is relayed by PCE1 and PCE2
along the PCE chain to PCE3, then PCE3 begins to compute the path along the PCE chain to PCE3, then PCE3 begins to compute the path
segments from the entry boundary nodes that provide connection from segments from the entry boundary nodes that provide connection from
AS2 to the destination (R12). But, to provide suitable path segments, AS2 to the destination (R12). But, to provide suitable path segments,
PCE3 must determine which entry boundary nodes provide connectivity PCE3 must determine which entry boundary nodes provide connectivity
to its upstream neighbor AS (identified by its AS number), and must to its upstream neighbor AS (identified by its AS number), and must
know the TE properties of the inter-AS TE links. In the same way, know the TE properties of the inter-AS TE links. In the same way,
PCE2 also needs to determine the entry boundary nodes according to PCE2 also needs to determine the entry boundary nodes according to
its upstream neighbor AS and the inter-AS TE link capabilities. its upstream neighbor AS and the inter-AS TE link capabilities.
Thus, to support Backward Recursive Path Computation the same Thus, to support Backward Recursive Path Computation the same
information as listed in Section 2.2 is required. information listed in Section 2.2 is required. The AS number of the
neighboring AS connected to by each inter-AS TE link is particular
important.
3. Extensions to OSPF-TE 3. Extensions to OSPF
Note that this document does not define mechanisms for distribution Note that this document does not define mechanisms for distribution
of TE information from one AS to another, does not distribute any of TE information from one AS to another, does not distribute any
form of TE reachability information for destinations outside the AS, form of TE reachability information for destinations outside the AS,
does not change the PCE architecture or usage, does not suggest or does not change the PCE architecture or usage, does not suggest or
recommend any form of TE aggregation, and does not feed private recommend any form of TE aggregation, and does not feed private
information between ASes. See section 2.1. information between ASes. See section 2.1.
The extensions defined in this document allow an inter-AS TE link The extensions defined in this document allow an inter-AS TE link
advertisement to be easily identified as such by the use of a new advertisement to be easily identified as such by the use of two new
link type. A new sub-TLV to the Link TLV is defined to carry the types of LSA, which are referred to as Inter-AS-TE-v2 LSA and Inter-
information about the neighboring AS. The extensions are equally AS-TE-v3 LSA. Three new sub-TLVs are added to the Link TLV to carry
applicable to TE distribution using OSPFv2 and OSPFv3. the information about the neighboring AS and the remote ASBR.
3.1. Remote AS Number Sub-TLV 3.1. LSA Definitions
As described in [OSPF-TE], the Link TLV describes a single link and 3.1.1. Inter-AS-TE-v2 LSA
consists of a set of sub-TLVs. A new sub-TLV, the Remote AS Number
sub-TLV is added to the Link TLV when advertising inter-AS links. The For the advertisement of OSPFv2 inter-AS TE links, a new Opaque LSA,
Remote AS Number sub-TLV specifies the AS number of the neighboring the Inter-AS-TE-v2 LSA, is defined in this document. The Inter-AS-TE-
AS to which the advertised link connects. The Remote AS number sub- v2 LSA has the same format as "Traffic Engineering LSA" which is
TLV is mandatory for an inter-AS TE link. defined in [OSPF-TE].
The inter-AS TE link advertisement SHOULD be carried in a Type 10
Opaque LSA if the flooding scope is to be limited to within the
single IGP area to which the ASBR belongs, or MAY be carried in a
Type 11 Opaque LSA if the information is intended to reach all
routers (including area border routers, ASBRs, and PCEs) in the AS.
The choice between the use of a Type 10 or Type 11 Opaque LSA is a
network-wide policy choice, and configuration control of it SHOULD be
provided in ASBR implementations that support the advertisement of
inter-AS TE links.
The Link State ID of an Opaque LSA as defined in [RFC2370] is divided
into two parts. One of them is the Opaque type (8-bit), the other is
the Opaque ID (24-bit). The suggested value for the Opaque type of
Inter-AS-TE-v2 LSA is TBD and will be assigned by IANA (see Section
6.1). We suggest the value 6. The Opaque ID (in this document called
the Instance) of the Inter-AS-TE-v2 LSA is an arbitrary value used to
uniquely identify Traffic Engineering LSAs. The Link State ID has no
topological significance.
The TLVs within the body of an Inter-AS-TE-v2 LSA have the same
format as used in OSPF-TE. The payload of the TLVs consists of one or
more nested Type/Length/Value triplets. New sub-TLVs specifically for
inter-AS TE Link advertisement are described in Section 3.2.
3.1.2. Inter-AS-TE-v3 LSA
In this document, a new LS type is defined for OSPFv3 inter-AS TE
link advertisement. The new LS type function code is 11 (which needs
to be confirmed by IANA see Section 6.1).
The format of an Inter-AS-TE-v3 LSA follows the standard definition
of an OSPFv3 LSA as defined in [OSPFV3].
The high-order three bits of the LS type field of the OSPFv3 LSA
header encode generic properties of the LSA and are termed the U-bit,
S2-bit, and S1-bit [OSPFV3]. The remainder of the LS type carries the
LSA function code.
For the Inter-AS-TE-v3-LSA the bits are set as follows:
The U-bit is always set to 1 to indicate that an OSPFv3 router MUST
flood the LSA at its defined flooding scope even if it does not
recognize the LS type.
The S2 and S1 bits indicate the flooding scope of an LSA. For the
Inter-AS-TE-v3-LSA the S2 and S1 bits SHOULD be set to 01 to indicate
that the flooding scope is to be limited to within the single IGP
area to which the ASBR belongs, but MAY be set to 10 if the
information should reach all routers (including area border routers,
ASBRs, and PCEs) in the AS. The choice between the use of 01 or 10 is
a network-wide policy choice, and configuration control SHOULD be
provided in ASBR implementations that support the advertisement of
inter-AS TE links.
The Link State ID of the Inter-AS-TE-v3 LSA is an arbitrary value
used to uniquely identify Traffic Engineering LSAs. The LSA ID has no
topological significance.
The TLVs with the body of an Inter-AS-TE-v3 LSA have the same format
and semantic as defined above in [OSPF-V3-TE]. New sub-TLVs
specifically for inter-AS TE Link advertisement are described in
Section 3.2.
3.2. LSA Payload
Both Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA contain one top level
TLV:
2 - Link TLV
For the Inter-AS-TE-v2 LSA this TLV is defined in [OSPF-TE] and for
the Inter-AS-TE-v3 LSA this TLV is defined in [OSPF-V3-TE]. The sub-
TLVs carried in this TLV are described in the following sections.
3.2.1. Link TLV
The Link TLV describes a single link and consists a set of sub-TLVs.
The sub-TLVs for inclusion in the Link TLV of the Inter-AS-TE-v2 LSA
and Inter-AS-TE-v3 LSA are defined respectively in [OSPF-TE] and
[OSPF-V3-TE] and the list of sub-TLVs may be extended by other
documents. However, this document defines one exception as follows.
The Link ID sub-TLV [OSPF-TE] MUST NOT be used in the Link TLV of an
Inter-AS-TE-v2 LSA, and the Neighbor ID sub-TLV [OSPF-V3-TE] MUST NOT
be used in the Link TLV of an Inter-AS-TE-v3 LSA. This is because the
address of the link-end or neighbor is an address in another AS that
may operate a different address space; such an address is of no value
to routing within the AS where this Link TLV is used.
Instead, the remote ASBR is identified by the inclusion of the
following new sub-TLVs defined in this document and described in the
subsequent sections.
21 - Remote AS Number sub-TLV
22 - IPv4 Remote ASBR ID sub-TLV
23 - IPv6 Remote ASBR ID sub-TLV
The Remote-AS-Number sub-TLV MUST be included in the Link TLV of both
the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA. At least one of the
IPv4-Remote-ASBR-ID sub-TLV and the IPv6-Remote-ASBR-ID sub-TLV
SHOULD be included in the Link TLV of the Inter-AS-TE-v2 LSA and
Inter-AS-TE-v3 LSA. Note that it is possible to include the IPv6-
Remote-ASBR-ID sub-TLV in the Link TLV of the Inter-AS-TE-v2 LSA, and
to include the IPv4-Remote-ASBR-ID sub-TLV in the Link TLV of the
Inter-AS-TE-v3 LSA because the sub-TLVs refer to ASBRs that are in a
different addressing scope (that is, a different AS) from that where
the OSPF LSA is used.
3.3. Sub-TLV Detail
3.3.1. Remote AS Number Sub-TLV
A new sub-TLV, the Remote AS Number sub-TLV is defined for inclusion
in the Link TLV when advertising inter-AS links. The Remote AS Number
sub-TLV specifies the AS number of the neighboring AS to which the
advertised link connects. The Remote AS number sub-TLV is REQUIRED in
a Link TLV that advertises an inter-AS TE link.
The Remote AS number sub-TLV is TLV type 21 (which needs to be The Remote AS number sub-TLV is TLV type 21 (which needs to be
confirmed by IANA), and is four octets in length. The format is as confirmed by IANA), and is four octets in length. The format is as
follows: follows:
0 1 2 3 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 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote AS Number | | Remote AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Remote AS number field has 4 octets. When only two octets are The Remote AS number field has 4 octets. When only two octets are
used for the AS number, as in current deployments, the left (high- used for the AS number, as in current deployments, the left (high-
order) two octets MUST be set to zero. order) two octets MUST be set to zero.
3.2. Inter-AS Link Type 3.3.2. IPv4 Remote ASBR ID Sub-TLV
To identify a link as an inter-AS link and allow easy identification A new sub-TLV, which is referred to as the IPv4 Remote ASBR ID sub-
of these new advertisements, a new Link Type value is defined for use TLV, can be included in the Link TLV when advertising inter-AS links.
in the Link Type sub-TLV. The value of the Link Type for an inter-AS The IPv4 Remote ASBR ID sub-TLV specifies the IPv4 identifier of the
point-to-point link is 3 (which needs to be confirmed by IANA). remote ASBR to which the advertised inter-AS link connects. This
could be any stable and routable IPv4 address of the remote ASBR. Use
of the TE Router ID is RECOMMENDED.
The use of multi-access inter-AS TE links is for future study. The IPv4 Remote ASBR ID sub-TLV is TLV type 22 (which needs to be
confirmed by IANA), and is four octets in length. Its format is as
follows:
3.3. Link ID 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For an inter-AS link, the Link ID carried in the Link ID sub-TLV is In OSPFv2 advertisements, the IPv4 Remote ASBR ID sub-TLV MUST be
the remote ASBR identifier which could be any address of the remote included if the neighboring ASBR has an IPv4 address. If the
ASBR(e.g., the TE Router ID, Router ID or interface address of the neighboring ASBR does not have an IPv4 address (not even an IPv4 TE
remote ASBR reached through this inter-AS link). The TE Router ID is Router ID), the IPv6 Remote ASBR ID sub-TLV MUST be included instead.
RECOMMENDED. An IPv4 Remote ASBR ID sub-TLV and IPv6 Remote ASBR ID sub-TLV MAY
both be present in a Link TLV in OSPFv2 or OSPFv3.
3.3.3. IPv6 Remote ASBR ID Sub-TLV
A new sub-TLV, which is referred to as the IPv6 Remote ASBR ID sub-
TLV, can be included in the Link TLV when advertising inter-AS links.
The IPv6 Remote ASBR ID sub-TLV specifies the identifier of the
remote ASBR to which the advertised inter-AS link connects. This
could be any stable, routable and global IPv6 address of the remote
ASBR. Use of the TE Router ID is RECOMMENDED.
The IPv6 Remote ASBR ID sub-TLV is TLV type 23 (which needs to be
confirmed by IANA), and is sixteen octets in length. Its format 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In OSPFv3 advertisements, the IPv6 Remote ASBR ID sub-TLV MUST be
included if the neighboring ASBR has an IPv6 address. If the
neighboring ASBR does not have an IPv6 address, the IPv4 Remote ASBR
ID sub-TLV MUST be included instead. An IPv4 Remote ASBR ID sub-TLV
and IPv6 Remote ASBR ID sub-TLV MAY both be present in a Link TLV in
OSPFv2 or OSPFv3.
4. Procedure for Inter-AS TE Links 4. Procedure for Inter-AS TE Links
When TE is enabled on an inter-AS link and the link is up, the ASBR When TE is enabled on an inter-AS link and the link is up, the ASBR
SHOULD advertise this link using the normal procedures for OSPF-TE SHOULD advertise this link using the normal procedures for OSPF-TE
[OSPF-TE]. When either the link is down or TE is disabled on the [OSPF-TE]. When either the link is down or TE is disabled on the
link , the ASBR SHOULD withdraw the advertisement. When there are link , the ASBR SHOULD withdraw the advertisement. When there are
changes to the TE parameters for the link (for example, when the changes to the TE parameters for the link (for example, when the
available bandwidth changes) the ASBR SHOULD re-advertise the link, available bandwidth changes) the ASBR SHOULD re-advertise the link,
but the ASBR MUST take precautions against excessive re- but the ASBR MUST take precautions against excessive re-
advertisements as described in [OSPF-TE]. advertisements as described in [OSPF-TE].
Hellos MUST NOT be exchanged (and consequently, an OSPF adjacency Hellos MUST NOT be exchanged over the inter-AS link, and
MUST NOT be formed) over the inter-AS link. consequently , an OSPF adjacency MUST NOT be formed.
The information advertised comes from the ASBR's knowledge of the TE The information advertised comes from the ASBR's knowledge of the TE
capabilities of the link, the ASBR's knowledge of the current status capabilities of the link, the ASBR's knowledge of the current status
and usage of the link, and configuration at the ASBR of the remote AS and usage of the link, and configuration at the ASBR of the remote AS
number and remote ASBR TE Router ID. number and remote ASBR TE Router ID.
The TE link advertisement SHOULD be carried in a Type 10 Opaque LSA
if the flooding scope is to be limited to within the single IGP area
to which the ASBR belongs, or MAY be carried in a Type 11 Opaque LSA
if the information should reach all routers (including area border
routers, ASBRs, and PCEs) in the AS. The choice between the use of a
Type 10 or Type 11 Opaque LSA is a network-wide policy choice, and
configuration control SHOULD be provided in ASBR implementations that
support the advertisement of inter-AS TE links.
Legacy routers receiving an advertisement for an inter-AS TE link are Legacy routers receiving an advertisement for an inter-AS TE link are
able to ignore it because the Link Type carries an unknown value. able to ignore it because the Link Type carries an unknown value.
They will continue to flood the LSA, but will not attempt to use the They will continue to flood the LSA, but will not attempt to use the
information received as if the link were an intra-AS TE link. information received as if the link were an intra-AS TE link.
Since there is no OSPF adjacency running on the inter-AS link, the In the current operation of TE OSPF, the LSRs at each end of a TE
local ASBR SHOULD do a "proxy" advertisement for the backward link emit LSAs describing the link. The databases in the LSRs then
direction of an inter-AS TE link, which facilitates a path have two entries (one locally generated, the other from the peer)
computation entity to do a 2-way check before including the link in a that describe the different 'directions' of the link. This enables
path computation. As the objective of such a "proxy" advertisement is CSPF to do a two-way check on the link when performing path
to avoid using an inter-AS TE link when the backward direction of the computation and eliminate it from consideration unless both
inter-AS TE link is unavailable or unsuitable, only some mandatory or directions of the link satisfy the required constraints.
essential TE information needs to be advertised, i.e. the Link ID,
the Link Type, and the Remote AS number of an inter-AS TE link.
Routers or PCEs that are capable of processing advertisements of In the case we are considering here(i.e., of a TE link to another AS)
inter-AS TE links SHOULD NOT use such links to compute paths that there is, by definition, no IGP peering and hence no bi-directional
exit an AS to a remote ASBR and then immediately re-enter the AS TE link information. In order for the CSPF route computation entity
through another TE link. Such paths would constitute extremely rare to include the link as a candidate path, we have to find a way to get
occurrences and SHOULD NOT be allowed except as the result of LSAs describing its (bidirectional) TE properties into the TE
specific policy configurations at the router or PCE computing the database.
path.
This is achieved by the ASBR advertising, internally to its AS,
information about both directions of the TE link to the next AS. The
ASBR will normally generate an LSA describing its own side of a link;
here we have it 'proxy' for the ASBR at the edge of the other AS and
generate an additional LSA that describes that device's 'view' of the
link.
Only some essential TE information for the link needs to be
advertised; i.e., the Link Type, the Remote AS number and the Remote
ASBR ID. Routers or PCEs that are capable of processing
advertisements of inter-AS TE links SHOULD NOT use such links to
compute paths that exit an AS to a remote ASBR and then immediately
re-enter the AS through another TE link. Such paths would constitute
extremely rare occurrences and SHOULD NOT be allowed except as the
result of specific policy configurations at the router or PCE
computing the path.
4.1. Origin of Proxied TE Information
Section 4 describes how to an ASBR advertises TE link information as
a proxy for its neighbor ASBR, but does not describe where this
information comes from.
Although the source of this information is outside the scope of this
document, it is possible that it will be a configuration requirement
at the ASBR, as are other, local, properties of the TE link. Further,
where BGP is used to exchange IP routing information between the
ASBRs, a certain amount of additional local configuration about the
link and the remote ASBR is likely to be available.
We note further that it is possible, and may be operationally
advantageous, to obtain some of the required configuration
information from BGP. Whether and how to utilize these possibilities
is an implementation matter.
5. Security Considerations 5. Security Considerations
The protocol extensions defined in this document are relatively minor The protocol extensions defined in this document are relatively minor
and can be secured within the AS in which they are used by the and can be secured within the AS in which they are used by the
existing OSPF security mechanisms. existing OSPF security mechanisms.
There is no exchange of information between ASes, and no change to There is no exchange of information between ASes, and no change to
the OSPF security relationship between the ASes. In particular, since the OSPF security relationship between the ASes. In particular, since
no OSPF adjacency is formed on the inter-AS links, there is no no OSPF adjacency is formed on the inter-AS links, there is no
requirement for OSPF security between the ASes. requirement for OSPF security between the ASes.
It should be noted, however, that some of the information included in Some of the information included in these new advertisements (e.g.,
these new advertisements(the remote AS number and the remote ASBR ID) the remote AS number and the remote ASBR ID) is obtained manually
are obtained from a neighboring administration and cannot be verified from a neighboring administration as part of commercial relationship.
in anyway. Since the means of delivery of this information is likely The source and content of this information should be carefully
to be part of a commercial relationship, the source of the checked before it is entered as configuration information at the ASBR
information should be carefully checked before it is entered as responsible for advertising the inter-AS TE links.
configuration information at the ASBR responsible for advertising the
inter-AS TE links. It is worth noting that in the scenario we are considering a Border
Gateway Protocol (BGP) peering may exist between the two ASBRs and
this could be used to detect inconsistencies in configuration. For
example, if a different remote AS number is received in a BGP OPEN
[BGP] from that locally configured into OSPF-TE, as we describe here,
then something is amiss. Note, further, that if BGP is used to
exchange TE information as described in Section 4.1, the inter-AS BGP
session will need to be fully secured.
6. IANA Considerations 6. IANA Considerations
IANA is requested to make the following allocations from registries IANA is requested to make the following allocations from registries
under its control. under its control.
6.1. OSPF LSA Sub-TLVs type 6.1. Inter-AS TE OSPF LSA
IANA is requested to assign a new Opaque LSA type (TBD) to Inter-AS-
TE-v2 LSA and a new OSPFv3 LSA type function code (TBD) to Inter-AS-
TE-v3 LSA. We suggest that the value 6 be assigned for the new Opaque
LSA type, and the value 11 be assigned for the new OSPV3 LSA type
function code.
6.2. OSPF LSA Sub-TLVs type
IANA maintains the "Open Shortest Path First (OSPF) Traffic IANA maintains the "Open Shortest Path First (OSPF) Traffic
Engineering TLVs" registry with sub-registry "Types for sub-TLVs in a Engineering TLVs" registry with sub-registry "Types for sub-TLVs in a
TE Link TLV". IANA is requested to assign a new sub-TLV as follows. TE Link TLV". IANA is requested to assign a new sub-TLV as follows.
The number 21 is suggested as shown in Section 3.1. The following number are suggested (see section 3.3):
Value Meaning Value Meaning
21 Remote AS Number sub-TLV. 21 Remote AS Number sub-TLV
6.2. OSPF TE Link Type
IANA is requested to create a new sub-registry "TE Link Types" of the
registry "Open Shortest Path First (OSPF) Traffic Engineering TLVs"
to track TE Link Types.
The sub-registry should read as follows:
[OSPF-TE] defines the Link Type sub-TLV of the Link TLV. The
following values are defined.
Value Meaning Reference
1 Point-to-point link [OSPF-TE]
2 Multi-access link [OSPF-TE]
3 Inter-AS link [this document] 22 IPv4 Remote ASBR ID sub-TLV
New allocations from this registry are by IETF Standards Action. 23 IPv6 Remote ASBR ID sub-TLV
7. Acknowledgments 7. Acknowledgments
The authors would like to thank Adrian Farrel, Acee Lindem, JP The authors would like to thank Adrian Farrel, Acee Lindem, JP
Vasseur, Dean Cheng, and Jean-Louis Le Roux for their review and Vasseur, Dean Cheng, and Jean-Louis Le Roux for their review and
comments to this document. comments to this document.
8. References 8. References
8.1. Normative References 8.1. Normative References
skipping to change at page 11, line 25 skipping to change at page 15, line 46
[RFC2370] R. Coltun, "The OSPF Opaque LSA Option", RFC2370, July [RFC2370] R. Coltun, "The OSPF Opaque LSA Option", RFC2370, July
1998. 1998.
[OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[OSPF-TE] Katz, D., Kompella, K., and Yeung, D., "Traffic Engineering [OSPF-TE] Katz, D., Kompella, K., and Yeung, D., "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September (TE) Extensions to OSPF Version 2", RFC 3630, September
2003. 2003.
[OSPF-V3-TE] Ishiguro K., Manral V., Davey A., and Lindem A. "Traffic
Engineering Extensions to OSPF version 3", draft-ietf-ospf-
ospfv3-traffic, {work in progress}.
[GMPLS-TE] Rekhter, Y., and Kompella, K., "OSPF Extensions in Support [GMPLS-TE] Rekhter, Y., and Kompella, K., "OSPF Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)", RFC of Generalized Multi-Protocol Label Switching (GMPLS)", RFC
4203, October 2005. 4203, October 2005.
[OSPFV3] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",
RFC 2740, April 1998.
8.2. Informative References 8.2. Informative References
[INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic [INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic
Engineering Requirements", RFC4216, November 2005. Engineering Requirements", RFC4216, November 2005.
[PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain [PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain
path computation method for establishing Inter-domain", path computation method for establishing Inter-domain",
draft-ietf-ccamp-inter-domain-pd-path-comp, (work in draft-ietf-ccamp-inter-domain-pd-path-comp, (work in
progress). progress).
[BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A Backward [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A Backward
Recursive PCE-based Computation (BRPC) procedure to compute Recursive PCE-based Computation (BRPC) procedure to compute
shortest inter-domain Traffic Engineering Label Switched shortest inter-domain Traffic Engineering Label Switched
Paths ", draft-ietf-pce-brpc, (work in progress) Paths ", draft-ietf-pce-brpc, (work in progress)
[PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation [PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation
Element (PCE)-Based Architecture", RFC4655, August 2006. Element (PCE)-Based Architecture", RFC4655, August 2006.
[OSPF-TE-V3] Ishiguro K., Manral V., Davey A., and Lindem A. "Traffic
Engineering Extensions to OSPF version 3", draft-ietf-ospf-
ospfv3-traffic, {work in progress}.
[OSPFV3] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC [OSPFV3] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC
2740, April 1998. 2740, April 1998.
[L1VPN-OSPF-AD] Bryskin, I., and Berger, L., "OSPF Based L1VPN Auto- [L1VPN-OSPF-AD] Bryskin, I., and Berger, L., "OSPF Based L1VPN Auto-
Discovery", draft-ietf-l1vpn-ospf-auto-discovery, (work in Discovery", draft-ietf-l1vpn-ospf-auto-discovery, (work in
progress). progress).
[BGP] Rekhter, Li, Hares, "A Border Gateway Protocol 4 (BGP-4)",
RFC4271, January 2006
Authors' Addresses Authors' Addresses
Mach Chen Mach Chen
Huawei Technologies Co.,Ltd Huawei Technologies Co.,Ltd
KuiKe Building, No.9 Xinxi Rd., KuiKe Building, No.9 Xinxi Rd.,
Hai-Dian District Hai-Dian District
Beijing, 100085 Beijing, 100085
P.R. China P.R. China
Email: mach@huawei.com Email: mach@huawei.com
Renhai Zhang Renhai Zhang
Huawei Technologies Co.,Ltd Huawei Technologies Co.,Ltd
KuiKe Building, No.9 Xinxi Rd., KuiKe Building, No.9 Xinxi Rd.,
Hai-Dian District Hai-Dian District
Beijing, 100085 Beijing, 100085
P.R. China P.R. China
Email: zhangrenhai@huawei.com Email: zhangrenhai@huawei.com
Xiaodong Duan
China Mobile
53A,Xibianmennei Ave,Xunwu District
Beijing, China
Email: duanxiaodong@chinamobile.com
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
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