OSPF Extensions for Broadcast Inter-AS TE LinkFutureweiBoston, MAUSAHuaimo.chen@futurewei.comVerizonUSAmehmet.toy@verizon.comVolta NetworksMcLeanVAUSAxufeng.liu.ietf@gmail.comFujitsuUSAliulei.kddi@gmail.comChina MobileNo.32 Xuanwumenxi Ave., Xicheng DistrictBeijing100032P.R. Chinali_zhenqiang@hotmail.comIBMNCUSAyyang1998@gmail.com
Routing
OSPF Working Group
This document presents extensions to
the Open Shortest Path First (OSPF)
for advertising broadcast inter-AS Traffic Engineering (TE) links.
Connections among different Autonomous Systems (ASes) may be
point-to-point (P2P) links and broadcast links.
For a P2P inter-AS TE link,
RFC 5392 defines a new Opaque LSA, the Inter-AS-TE-v2 LSA,
for advertising the OSPFv2 link; and
a new OSPFv3 LS type, Inter-AS-TE-v3 LSA,
for advertising the OSPFv3 link.
Both the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA
contain one top level TLV:
Link TLV
The Link TLV describes a single link and includes a set of sub-TLVs.
The Link ID sub-TLV defined in RFC 3630 MUST NOT
be used in the Link TLV of an Inter-AS-TE-v2 LSA,
and the Neighbor ID sub-TLV defined in RFC 5329 MUST NOT
be used in the Link TLV of an Inter-AS-TE-v3 LSA.
Instead, the remote ASBR is identified by the inclusion
of Remote AS Number sub-TLV and
IPv4/IPv6 Remote ASBR ID sub-TLV, which is defined in RFC 5392.
For a P2P inter-AS link, the information about
its remote ASBR for replacing its link ID may be configured.
For a broadcast inter-AS link,
its link ID is the interface IP address of the designated router (DR)
of the link in OSPF.
Since no OSPF runs over any broadcast inter-AS link,
no DR or backup DR (BDR) is selected.
It is hard to configure a replacement for DR and BDR.
This document presents extensions to OSPF
for advertising broadcast inter-AS TE links through
defining a new sub-TLV for a broadcast link
without configuring any replacement for DR and BDR on the link.
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 .For a broadcast link connecting multiple ASBRs
in a number of ASes,
on each of the ASBRs X, the following information about the link
may be obtained:
No remote IP address or link ID (i.e., DR's interface address)
may be obtained.
Two new sub-TLVs are defined.
One is for local IPv4 address with mask length; and
the other is for local IPv6 address with mask length.
The format of the sub-TLV for a local IPv4 address with
mask length is shown as follows.
The IPv4 Address indicates the local IPv4 address of a link.
The Mask Length indicates the length of the IPv4 address mask.
The format of the sub-TLV for a local IPv6 address with
mask length is illustrated below.
The IPv6 Address indicates the local IPv6 address of a link.
The Mask Length indicates the length of the IPv6 address mask.
For a broadcast inter-AS link connecting to multiple ASBRs,
each of the ASBRs as an OSPF router advertises
an LSA (Inter-AS-TE-v2 LSA for OSPFv2 or Inter-AS-TE-v3 LSA for OSPFv3)
with a link TLV containing sub-TLVs for
the information such as 1) 10 8) on the broadcast link
described in Section 3.
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. When either the link is down or TE is disabled on the
link, the ASBR SHOULD withdraw the advertisement. When there are
changes to the TE parameters for the link (for example, when the
available bandwidth changes), the ASBR SHOULD re-advertise the link
but MUST take precautions against excessive re-advertisements.
Suppose that there is a super node,
which just receives LSAs from each of ASes (or domains)
through a passive OSPF adjacency between the super node and
an ASBR or ABR in the AS or domain.
For a new broadcast link connecting multiple routers with no link ID
configured, when the super node receives an LSA containing the link
attached to router X, it stores the link from X into its TED.
It finds the link's remote end P
using the link's local IP address with network mask. P is a Pseudo
node identified by the local IP address of the DR
selected from the routers connected to the link. After finding P, it
associates the link attached to X with P and
the link connected to P with X.
If P is not found, a new Pseudo node P is created.
The super node associates the link attached to X with P and
the link attached to P with X.
This creates a bidirectional connection between X and P.
The first router and second router from which the super node receives
an LSA containing the link are selected as the DR and
BDR respectively. After the DR is down, the
BDR node becomes the DR and the router other
than the DR with the largest (or smallest) local IP address connecting
to the link is selected as the BDR.
When the old DR is down and the BDR
becomes the new DR, the super node updates its TED through
removing the link between each of routers X and old P (the Pseudo node
corresponding to the old DR) and adding a link between
each of routers X (still connecting to the broadcast link) and new P
(the Pseudo node corresponding to the new DR).
The mechanism described in this document does not raise any new security issues for the OSPF protocols.This section specifies requests for IANA allocation.The authors would like to thank all
for their valuable comments on this draft.