Advertisement of Stub Link Attributes
draft-wang-lsr-stub-link-attributes-06
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Active".
|
|
|---|---|---|---|
| Authors | Aijun Wang , Zhibo Hu, Acee Lindem , Gyan Mishra , Jinsong Sun | ||
| Last updated | 2023-04-02 | ||
| Replaces | draft-wang-lsr-passive-interface-attribute | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Call For Adoption By WG Issued | |
| Document shepherd | Christian Hopps | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | chopps@chopps.org |
draft-wang-lsr-stub-link-attributes-06
LSR Working Group A. Wang
Internet-Draft China Telecom
Intended status: Standards Track Z. Hu
Expires: 5 October 2023 Huawei Technologies
A. Lindem
LabN Consulting LLC
G. Mishra
Verizon Inc.
J. Sun
ZTE Corporation
3 April 2023
Advertisement of Stub Link Attributes
draft-wang-lsr-stub-link-attributes-06
Abstract
This document describes the mechanism that can be used to advertise
the stub link attributes within the IS-IS or OSPF domain.
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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Task Force (IETF). Note that other groups may also distribute
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 5 October 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Consideration for Identifying Stub Link . . . . . . . . . . . 3
4. Protocol Extension for Stub Link Attributes . . . . . . . . . 3
4.1. OSPF Stub-Link TLV . . . . . . . . . . . . . . . . . . . 3
4.2. IS-IS Stub-link TLV . . . . . . . . . . . . . . . . . . . 4
4.3. IPv4 Prefix Sub-TLV . . . . . . . . . . . . . . . . . . . 5
4.4. IPv6 Prefix Sub-TLV . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Applied Scenarios . . . . . . . . . . . . . . . . . 9
A.1. Inter-AS topology recovery . . . . . . . . . . . . . . . 9
A.2. Egress Engineering for Anycast Servers . . . . . . . . . 11
A.3. Optimized BGP Next-hop Selection . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
Stub links are used commonly within enterprise or service provider
networks. One common use case is the inter-AS routing scenario where
there are no IGP adjacencies between the adjacent BGP domains,
another use case is at the network boundary that the interfaces are
used to connect to the application servers.
For operators that have multiple ASes interconnecting with each other
via the stub links, there is a requirement to obtain the inter-AS
topology information as described in
[I-D.ietf-idr-bgpls-inter-as-topology-ext]. To achieve such goal, it
is required that the BGP-LS to be enabled on every router that has
the stub links, which is challenging for the network operation. It
is desirable to advertise the stub link info into the IGP to ease the
deployment of BGP-LS on any router in the IGP domain.
For stub links that are used to connect the servers, knowing the
status of these stub links can facilitate the routers within the IGP
to accomplish TE tasks in some scenarios.
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But OSPF and IS-IS have no capability to identify such stub links and
their associated attributes now.
This document defines the protocol extension for OSPFv2/v3 and IS-IS
to indicate the stub links and their associated attributes.
2. 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] .
3. Consideration for Identifying Stub Link
OSPF[RFC5392] defines the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA
to carry the TE information about inter-AS links. IS-IS[RFC5316]
defines the Inter-AS Reachability TLV to carry the TE information
about inter-AS links. But they are normally being used under RSVP-
TE, especially inter-domain RSVP-TE scenarios. As illustrated in the
potential scenarios that described in Appendix A, there is still the
need for a generic solution which also covers non inter-AS stub
links.
Then, to solve the problems that described in the applied scenarios,
this document defines the Stub-Link TLV to identify the stub link and
transmit the associated attributes for OSPF and IS-IS respectively.
4. Protocol Extension for Stub Link Attributes
The following sections define the protocol extension to indicate the
stub link and its associated attributes in OSPFv2/v3 and IS-IS.
4.1. OSPF Stub-Link TLV
This document defines the Stub-Link TLV to describe stub link of a
single router.
For OSPFv2, the newly defined Stub-Link TLV is named as OSPFv2
Extended Stub-Link TLV, which is included in the OSPFv2 Extended Link
Opaque LSA [RFC7684]
For OSPFv3, the newly defined Stub-Link TLV is named as OSPFv3
Extended Stub-Link TLV, which is included in the OSPFv3 E-Link-LSA
[RFC8362]
OSPFv2 Extended Stub-Link TLV and OSPFv3 Extended Stub-Link TLV has
the following same format:
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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(Stub-Link) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Prefix Sub-TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Existing Sub-TLVs (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: OSPF Stub-Link TLV
Type: The TLV type. The value is 2(TBD) for OSPFv2 Extended Link
Stub-Link TLV under the IANA codepoint "OSPFv2 Extended Link Opaque
LSA TLVs", and is 10(TBD) for OSPFv3 Router-Stub-Link TLV under the
IANA codepoint "OSPFv3 Extended-LSA TLVs"
Length: Variable, dependent on sub-TLVs
Flags: Define the type of the stub-link:
* U bit(bit 0): Identify the unnumbered stub link if this bit is
set.
* bit 1-bit 15: Reserved
Link Prefix Sub-TLV: The prefix of the stub-link. It's format is
defined in Section 4.3 and Section 4.4.
Existing Sub-TLVs: Sub-TLV that defined within "OSPFv2 Extended Link
TLV Sub-TLVs" and "OSPFv3 Extended-LSA Sub-TLVs" can be included if
necessary.
If the stub-link is identified as unnumbered stub link (U bit is
set), then the "Remote IPv4 Address sub-TLV" or "Remote Interface
IPv6 Address sub-TLV", which should be set to the identifier value of
remote router, SHOULD be included to facilitate the pairing of inter-
AS link.
This document creates a registry for Stub-Link attributes in
Section 6.
4.2. IS-IS Stub-link TLV
This document defines the IS-IS Stub-Link TLV to describes stub link
of a single router.
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The IS-IS Stub-Link TLV has 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(Stub-Link) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Prefix Sub-TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Existing Sub-TLVs(Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: IS-IS Stub-Link TLV
Type: IS-IS TLV codepoint. Value is 151 (TBD) for stub-link TLV.
Length: Variable, dependent on sub-TLVs
Flags: Define the type of the stub-link:
* 0: U bit(bit 0): Identify the unnumbered stub link if this bit is
set.
* bit 1-bit 15: Reserved
Link Prefix Sub-TLV: The prefix of the stub-link. It's format is
defined in Section 4.3 and Section 4.4.
Existing Sub-TLVs: Sub-TLVs that defined within "IS-IS Sub-TLVs for
TLVs Advertising Neighbor Information " can be included if necessary.
If the stub-link is identified as unnumbered stub link type (U bit is
set), then the "IPv4 Remote ASBR ID" or "IPv6 Remote ASBR ID" sub-TLV
SHOULD be included to facilitate the pairing of inter-AS link.
4.3. IPv4 Prefix Sub-TLV
The IPv4 Prefix Sub-TLV has 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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: IPv4 Prefix Sub-TLV
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Type: IPv4 Prefix Sub-TLV codepoint. Value is 25(TBD) for OSPFv2
(under "OSPFv2 Extended Link Sub-TLVs" )
30(TBD) for OSPFv3(under OSPFv3 Extended-LSA Sub-TLVs)
45(TBD) for IS-IS(under "IS-IS Sub-TLVs for TLVs Advertising Neighbor
Information")
Length: Netmask length value of the IPv4 Prefix. Value should be in
2-32.
IPv4 Prefix: The value of 4-octet IPv4 Prefix address, the host part
should be zero.
4.4. IPv6 Prefix Sub-TLV
The IPv6 Prefix Sub-TLV has 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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: IPv6 Prefix Sub-TLV
Type: IPv6 Prefix Sub-TLV codepoint. Value is 31(TBD) for
OSPFv3.(under OSPFv3 Extended-LSA Sub-TLVs)
46(TBD) for IS-IS(under "IS-IS Sub-TLVs for TLVs Advertising Neighbor
Information")
Length: Netmask length value of the IPv6 Prefix. Value should be in
2-128.
IPv6 Prefix: The value of 16-octet IPv6 Prefix address, the host part
should be zero.
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5. Security Considerations
Security concerns for IS-IS are addressed in [RFC5304] and[RFC5310]
Security concern for OSPFv3 is addressed in [RFC4552]
Advertisement of the additional information defined in this document
introduces no new security concerns.
6. IANA Considerations
IANA is requested to the allocation in following registries:
+====================================+============+=============================+
| Registry | Type | Meaning |
| |(suggested) | |
+====================================+============+=============================+
|OSPFv2 Extended Link Opaque LSA TLVs| 2 |OSPFv2 Extended Stub-Link |
+------------------------------------+------------+-----------------------------+
|OSPFv3 Extended-LSA TLVs | 10 |OSPFv3 Extended Stub-Link |
+------------------------------------+------------+-----------------------------+
|IS-IS Top-Level TLV | 151 |IS-IS Stub-Link |
+------------------------------------+------------+-----------------------------+
|OSPFv2 Extended Link TLV | 25 | IPv4 Prefix |
+------------------------------------+------------+-----------------------------+
|OSPFv3 Extended-LSA Sub-TLVs | 30 | IPv4 Prefix |
+------------------------------------+------------+-----------------------------+
|OSPFv3 Extended-LSA Sub-TLVs | 31 | IPv6 Prefix |
+------------------------------------+------------+-----------------------------+
|IS-IS Sub-TLVs for TLVs | | |
|Advertising Neighbor Information | 45 | IPv4 Prefix |
+------------------------------------+------------+-----------------------------+
|IS-IS Sub-TLVs for TLVs | | |
|Advertising Neighbor Information | 46 | IPv6 Prefix |
+------------------------------------+------------+-----------------------------+
Figure 5: IANA Allocation for newly defined TLVs and Sub-TLVs
7. Acknowledgement
Thanks Ketan Talaulikar, Shunwan Zhang, Peter Psenak, Tony Li, Les
Ginsberg, Dhruv Dhody, Jeff Tantsura and Robert Raszuk for their
suggestions and comments on this idea.
8. References
8.1. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<https://www.rfc-editor.org/info/rfc4552>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <https://www.rfc-editor.org/info/rfc5310>.
[RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316,
December 2008, <https://www.rfc-editor.org/info/rfc5316>.
[RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392,
January 2009, <https://www.rfc-editor.org/info/rfc5392>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <https://www.rfc-editor.org/info/rfc7684>.
[RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
F. Baker, "OSPFv3 Link State Advertisement (LSA)
Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
2018, <https://www.rfc-editor.org/info/rfc8362>.
8.2. Informative References
[I-D.ietf-idr-bgpls-inter-as-topology-ext]
Wang, A., Chen, H., Talaulikar, K., and S. Zhuang, "BGP-LS
Extension for Inter-AS Topology Retrieval", Work in
Progress, Internet-Draft, draft-ietf-idr-bgpls-inter-as-
topology-ext-12, 3 April 2023,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-idr-bgpls-inter-as-topology-ext/>.
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Appendix A. Applied Scenarios
The following sections describe the scenarios that knowing the stub
link related attributes information can help solve the corresponding
necessity in questions.
A.1. Inter-AS topology recovery
Figure 1 describes the scenario that the necessity of inter-AS
topology recovery for Native IP point-to-point stub link scenario.
R10, R11 and R12 are located in AS1. R20, R21,R22 are located in
AS2. The controller runs BGP-LS with R10 in AS1 and R20 in AS2
respectively.
There is one BGP session among the border router R11 and R21, which
are connected by several stub links(passive interfaces) between them.
The situation within the R21 and R22 are the same.
Since the links between the border routers are passive, there will be
no IGP neighbors between them. The BGP-LS information carried in
each AS will not report these stub links,and the controller can't
recovery the inter-AS topology automatically.
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+----------+
+--------------+Controller+--------------+
^ +----------+ ^
| |
BGP-LS| |BGP-LS
| +---+BGP+----+ |
+-----------------+ +-------------------+
| | | | | |
| | +---+-+ +-+---+ | |
| | | +--------+ | | |
| +--------+R11 |--------| R21+----------+ |
| | | +--------+ | | |
| | +---+-+ +-+---+ | |
| +--+--+ | | +--+--+ |
| | | | | | | |
| |R10 | | | |R20 | |
| | | | | | | |
| +--+--+ +---+-+ +-+---+ +--+--+ |
| | | +--------+ | | |
| +--------+R12 |--------| R22+----------+ |
| | +--------+ | |
| +---+-+ +-+---+ |
| | | |
+--------AS1------+ +----------AS2------+
+---+BGP+----+
Figure 1: Inter-AS Topology Recovery(P2P Scenario)
Figure 2 describes the similar situation but in LAN environment. The
border routers of AS1, AS2 and AS3 are connected via one LAN
interfaces(that is to say, the corresponding interfaces on R1, R2 and
R3 are on the same subnet). There are three different BGP sessions
from the loopback address of the border routers among them
respectively. It is necessary to recovery the underlying inter-AS
topology automatically.
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+---------+ +---------+
| | | |
| +--+--+ +--+--+ |
| | | | | |
| |R1 +-------+ +------+R2 | |
| | | | | | | |
| +--+--+ | | +--+--+ |
| | | | | |
+---AS1---+ | | +----AS2--+
+-+-+-+
| |
| SW |
| |
+--+--+
|
+--+--+
+--+ +--+
| | R3 | |
| +-----+ |
| |
| |
+-----AS3---+
Figure 2: Inter-AS Topology Recovery(LAN Scenario)
A.2. Egress Engineering for Anycast Servers
Figure 3 describes the scenario that the stub link information can be
used for egress engineering for Anycast servers that connected to the
network. In the example, the R1, R2 and R3 are border routers which
are connected directly the server S1, S2 and S3 that have the same IP
address IPa. The characteristics of the stub links that connected to
these Anycast servers are different. It will be help for the router
R0, to know the attributes of the stub links and select the optimal
Anycast server to serve the customer's application.
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+----------------+
| |
| +---+-+ +-----+
| | | | S1 |
| +-------+R1 +------+ |
| | | | |(IPa)|
| | +---+-+ +-----+
| | |
| +--+--+ +---+-+ +-----+
| | | | | | S2 |
| |R0 +----+R2 +------+ |
| | | | | |(IPa)|
| +--+--+ +---+-+ +-----+
| | |
| | +---+-+ +-----+
| | | | | S3 |
| +-------+R3 +------+ |
| | | |(IPa)|
| +---+-+ +-----+
| |
+----------------+
Figure 3: Egress Engineering for Anycast Server
A.3. Optimized BGP Next-hop Selection
Figure 4 describes the scenario that the stub link information can
facilitate the optimized BGP next hop selection. The router R10 and
R20 which are located in different AS establish the BGP session
directly, with the explicit route set on each other which point to
the egress stub interface between the border routers. The attributes
of the stub links among the border routers are vary. It is certainly
will be helpful for the router R10 and R20 to select the optimized
BGP next hop, that is via the stub links among them, to reach each
other.
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|<---------------+BGP+------------------>|
| |
| |
+-----------------+ +-------------------+
| | | | | |
| | +---+-+ +-+---+ | |
| | | +--------+ | | |
| +--------+R11 |--------| R21+----------+ |
| | | +--------+ | | |
| | +---+-+ +-+---+ | |
| +--+--+ | | +--+--+ |
| | | | | | | |
| |R10 | | | |R20 | |
| | | | | | | |
| +--+--+ +---+-+ +-+---+ +--+--+ |
| | | +--------+ | | |
| +--------+R12 |--------| R22+----------+ |
| | +--------+ | |
| +---+-+ +-+---+ |
| | | |
+-------+AS1+-----+ +---------+AS2+-----+
Figure 4: Optimized BGP next hop selection
Authors' Addresses
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing
102209
China
Email: wangaj3@chinatelecom.cn
Zhibo Hu
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing
100095
China
Email: huzhibo@huawei.com
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Acee Lindem
LabN Consulting LLC
No. 301 Midenhall Way
Cary, NC 27513
United States of America
Email: acee.ietf@gmail.com
Gyan S. Mishra
Verizon Inc.
13101 Columbia Pike
Silver Spring, MD 20904
United States of America
Email: gyan.s.mishra@verizon.com
Jinsong Sun
ZTE Corporation
No. 68, Ziijnhua Road
Nan Jing
210012
China
Email: sun.jinsong@zte.com.cn
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