Internet DRAFT - draft-hares-idr-nexthop-path-record
draft-hares-idr-nexthop-path-record
Network Working Group S. Hares
Internet-Draft Z. Li
Intended status: Standards Track L. Zhang
Expires: December 31, 2015 Huawei Technologies
June 29, 2015
Record NEXTHOP_PATH ATTIBUTE for BGP
draft-hares-idr-nexthop-path-record-00
Abstract
In some BGP deployments, BGP next hops may use a set or tunnels or
run across converged networks such as seamless MPLS. This document
describes a new optional transitive path attribute, NEXTHOP_PATH
ATTRIBUTE for BGP that records the next hop path which can be used by
BGP network management to monitor and manage the BGP infrastructure
via management interfaces (such as I2RS).
Requirements Language
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 RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on December 31, 2015.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definition of NEXTHOP_PATH_RECORD ATTRIBUTE . . . . . . . . . 2
3. Process of NEXTHOP_PATH_RECORD ATTRIBUTE . . . . . . . . . . 4
3.1. Creating and Modifying the NEXTHOP_PATH Attribute . . . . 4
3.2. Error handling of NEXTHOP_PATH_RECORD Attribute . . . . . 5
4. Deployment considerations . . . . . . . . . . . . . . . . . . 5
4.1. BGP Tunnels . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Customized Best Path Selection . . . . . . . . . . . . . 5
4.3. Use in Seamless MPLS case with PE-RR . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Network topologies may use BGP to become more highly interconnected
via tunnels [I-D.rosen-idr-tunnel-encaps] or become interconnected
carrier MPLS networks that [I-D.ietf-mpls-seamless-mpls] with
multiple IGPs connected by IBGP into a single AS. In addition, BGP
provides teh ability to use provide additions paths
[I-D.ietf-idr-add-paths], or use custom decision paths
[I-D.ietf-idr-custom-decision] This document proposes a new path
attribute that can record the next hop path of the route to help
network management debugging of these new scenarios.
2. Definition of NEXTHOP_PATH_RECORD ATTRIBUTE
The NEXTHOP_PATH_RECORD ATTRIBUTE is an optional transitive BGP Path
Attribute. The NEXTHOP_PATH_RECORD ATTRIBUTE type is defined as
below (refer to [RFC4271] ):
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0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr. Flags |Attr. Type Code|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 NEXTHOP_PATH_RECORD ATTRIBUTE Type definition
Attr. Flags
SHOULD be optional transitive
Attr. Type Code
SHOULD be allocated by IANA
NEXTHOP_PATH is composed of a sequence of next hop path segments.
Each next hop path segment is represented by a triple <path segment
type, path segment length, path segment value>. The format of the
next hop path segment is shown in the figure 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Hop |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3 NH_SEQUENCE_V4 TLV
Type: A single octet encoding the TLV Type of path segement. The
Type of NH_SEQENCE_V4 is defined in this document, which needs to be
allocated by IANA. A registry for other types of NH Path segements
should be established by IANA.
Length: Two octets encoding the length in octets of the TLV,
including the type and length fields. The length is encoded as an
unsigned binary integer.
Reserved: A single octet that must be zero now.
NextHop: This contains a variable length of NextHops. For type
NH_SEQUENCE_V4 the length of this value is four octets.
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3. Process of NEXTHOP_PATH_RECORD ATTRIBUTE
The NEXTHOP_PATH attribute defined in this section is an optional
transitive BGP Path Attribute as described in [RFC4271].
3.1. Creating and Modifying the NEXTHOP_PATH Attribute
When a BGP speaker distributes a route to its BGP peer within UPDATE
message, the NEXTHOP_PATH ATTRIBUTE should be processed based on
different route states:
1. If the route is originated in this BGP speaker
* If the NEXTHOP_PATH ATTRIBUTE is supported, the NEXTHOP_PATH
ATTRIBUTE SHOULD be originated including the BGP speaker's own
next hop address in a next hop path segment. In this case,
the next hop address of the originating BGP speaker will be
the only entry of the next hop path segment, and this path
segment will be the only segment in NEXTHOP_PATH ATTRIBUTE.
* If the NEXTHOP_PATH_RECORD ATTRIBUTE is not supported, the
route will be distributed without NEXTHOP_PATH ATTRIBUTE.
2. if the route is received from one BGP speaker's UPDATE message
and and the NEXTHOP_PATH_RECORD is enabled and the nexthop is
changed (via nexthop self or other means)
* If the NEXTHOP_PATH_RECORD ATTRIBUTE is NULL the NEXTHOP_PATH
ATTRIBUTE SHOULD be originated including the BGP speaker's own
next hop address in a next hop path segment. In this case,
the next hop address of this BGP speaker will be the only
entry to the next hop path segment, and this path segment will
be the only segment in NEXTHOP_PATH ATTRIBUTE
* If the NEXTHOP_PATH_RECORD ATTRIBUTE is non-NULL and the local
BGP speaker support NEXTHOP_PATH ATTRIBUTE, when the route is
propagated to another IBGP speaker with next hop self (NHS ),
the BGP speaker MUST appends its own next hop address as the
last one of the next hop path segments.
3. If the NEXTHOP_PATH_RECORD ATTRIBUTE is non-NULL and the local
BGP speaker support NEXTHOP_PATH ATTRIBUTE, when the route is
propagated to another BGP speaker without changing the next hop
by the BGP speaker, the BGP speaker MUST NOT change the next hop
path sequence.
4. If the BGP does not support the NEXTHOP_PATH record, it should
keep the NEXTHOP_PATH RECORD unchanged.
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3.2. Error handling of NEXTHOP_PATH_RECORD Attribute
If there are errors in the internal format of the NEXTHOP_PATH
attribute, this attribute should simply be discarded as
[I-D.ietf-idr-error-handling] specifies in section 3 as Attribute
discard. The NEXTHOP_PATH_RECORD simply records nexthop information
for monitoring.
4. Deployment considerations
Two deployment examples are given to demonstrate how the nexthop
information can be deployed in existing BGP technologies to monitor
and tune the BGP clouds (IBGP or EBGP) to provide better operation.
maintenance. This attribute has records information.
4.1. BGP Tunnels
The [I-D.rosen-idr-tunnel-encaps] describes how BGP nexthop can be a
set of tunnels. NEXTHOP_PATH_RECORD attribute can allow BGP routers
to record when the BGP nexthop changes.
4.2. Customized Best Path Selection
The next_hop information gathered on an IBGP or EBP route could be
used by off-line decision processing to select paths, and re-inserted
as policy to affect the decision making via I2RS. The I2RS BGP use
case draft [I-D.keyupate-idr-i2rs-bgp-usecases] describes this its
section on customized best path selection (section 4.1) which uses
the BGP feature [I-D.ietf-idr-custom-decision] to set a custom
decision community.
4.3. Use in Seamless MPLS case with PE-RR
In a Seamless MPLS network [I-D.ietf-mpls-seamless-mpls], the Area
Border Routers (ABRs) which run IBGP may act RR-clients or be part of
RR mesh as described in section 5.1.7. Seamless MPLS places
restrictions on the BGP NEXT_HOP to make Seamless MPLS work in the
general case, but this may be tuned by tunnels or additional paths or
other mechanism.
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Inline RR Inline RR Inline RR
+------+ +------+ +------+
/ |ABR-a |---------|ABR-b |--------|ABR-c |
/ +------+ +------+ +------+\
/ | | | \
+-----+/ | | | \
|PE1 | IGP area1 | IGP area2 | IGP area3 | IGP area4 \+-----+
+-----+\ | | | | PE2|
\ | | | /+-----+
\ +------+ +------+ +---- -+ /
\|ABR-a'|---------|ABR-b'|--------|ABR-c'| /
+------+ +------+ +---- -+/
Inline RR Inline RR Inline RR
Figure 1 Seamless MPLS Network with Multiple IGP Areas
NEXTHOP_PATH_RECORD attribution may aid in monitoring paths in this
complex paths that may consists of tunnels, customized paths, or
Seamless MPLS topology.
5. IANA Considerations
IANA need to assign the codepoint in the "BGP Path Attributes"
registry to the NEXTHOP_PATH_RECORD ATTRIBUTE.
IANA shall create a registry for "next hop path segment". The type
field consists of a single octet, with possible values from 0 to 255.
The allocation policy for this field is to be "Standards Action with
Early Allocation". A new Type should be defined as "NH_SEQUENCE_V4".
6. Security Considerations
Note that, the NEXTHOP_PATH ATTRIBUTE is defined as a optional
transitive BGP Path attribute. Both the IBGP and EBGP speaker can
use this attribute. When an ASBR propagates the route receive from a
IBGP peer to an EBGP peer, the NEXTHOP_PATH ATTRIBUTE will be
distribute to the EBGP Speaker which may be controlled by other
Service Provider. If the EBGP speaker can support the NEXTHOP_PATH
ATTRIBUTE, it can parse the NEXTHOP_PATH ATTRIBUTE to get the inner
network architecture of the other network.
BGP requires the use of TCP-MD5 TCP-MD5 [RFC2385] or TCP-AO
[RFC5925]). Use of encryption will prevent unauthorized view of the
NEXTHOP_PATH. For those not supporting the required TCP-MD5 or TCP-
AO, the NEXTHOP_PATH ATTRIBUTE capability SHOULD disabled for
specific BGP speaker to prevent this attack.
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7. References
7.1. Normative References
[I-D.ietf-idr-error-handling]
Chen, E., Scudder, J., Mohapatra, P., and K. Patel,
"Revised Error Handling for BGP UPDATE Messages", draft-
ietf-idr-error-handling-19 (work in progress), April 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5
Signature Option", RFC 2385, August 1998.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010.
7.2. Informative References
[I-D.ietf-idr-add-paths]
Walton, D., Retana, A., Chen, E., and J. Scudder,
"Advertisement of Multiple Paths in BGP", draft-ietf-idr-
add-paths-10 (work in progress), October 2014.
[I-D.ietf-idr-custom-decision]
Retana, A. and R. White, "BGP Custom Decision Process",
draft-ietf-idr-custom-decision-06 (work in progress),
April 2015.
[I-D.ietf-mpls-seamless-mpls]
Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz,
M., and D. Steinberg, "Seamless MPLS Architecture", draft-
ietf-mpls-seamless-mpls-07 (work in progress), June 2014.
[I-D.keyupate-idr-i2rs-bgp-usecases]
Patel, K., White, R., and S. Hares, "Use Cases for an
Interface to BGP Protocol", draft-keyupate-idr-i2rs-bgp-
usecases-00 (work in progress), May 2015.
[I-D.rosen-idr-tunnel-encaps]
Rosen, E., Patel, K., and G. Velde, "Using the BGP Tunnel
Encapsulation Attribute without the BGP Encapsulation
SAFI", draft-rosen-idr-tunnel-encaps-00 (work in
progress), June 2015.
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Authors' Addresses
Susan Hares
Huawei Technologies
7453 Hickory Hill
Saline, MI 48176
USA
Email: shares@ndzh.com
Zhenbin Li
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
Li Zhang
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: monica.zhangli@huawei.com
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