Passive Interface Attribute
draft-wang-lsr-passive-interface-attribute-03
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 "Replaced".
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|
|---|---|---|---|
| Authors | Aijun Wang , Zhibo Hu, Gyan Mishra | ||
| Last updated | 2020-09-27 | ||
| Replaced by | draft-wang-lsr-stub-link-attributes | ||
| RFC stream | (None) | ||
| Formats | |||
| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
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| Send notices to | (None) |
draft-wang-lsr-passive-interface-attribute-03
LSR Working Group A. Wang
Internet-Draft China Telecom
Intended status: Standards Track Z. Hu
Expires: April 1, 2021 Huawei Technologies
G. Mishra
Verizon Inc.
September 28, 2020
Passive Interface Attribute
draft-wang-lsr-passive-interface-attribute-03
Abstract
This document describes the mechanism that can be used to
differentiate the passive interfaces from the normal interfaces
within ISIS or OSPF domain.
Status of This Memo
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This Internet-Draft will expire on April 1, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Scenario Description . . . . . . . . . . . . . . . . . . . . 3
4. Passive Interface Attribute . . . . . . . . . . . . . . . . . 4
4.1. ISIS Passive Interface Attribute . . . . . . . . . . . . 4
4.2. OSPF Passive Interface Attribute . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Passive interfaces are used commonly within an operators enterprise
or service provider networks. One of the most common use cases for
passive interface is in a data center Layer 2 and Layer 3 TOR(Top of
Rack) switch where the inter connected link between the TOR switches
and uplink to the Core switch are only a few links and a majority of
the links are Layer 3 VLAN Switched Virtual Interface Default
Gateways trunked betwen the TOR switches servicing Layer 2 broadcast
domains. In this scenario all the VLANs are made passive as it is
recommended to limit the number of network LSAs between routers and
switches to avoid unnecessary hello processing overhead.
Another common use case is an inter-as routing scenario where the
same routing protocol but diffent IGP instance is running between the
adjacent BGP domains. Using passive interface on the inter-as
tiepoint connections can ensure that prefixes contained within a
domain are only reachable within the domain itself and not allow the
link state database to be merged between domain which could result in
undesirable consequences.
For operator which runs different IGP domains that interconnect with
each other, there is desire to obtain the inter-as topology
information as described in
[I-D.ietf-idr-bgpls-inter-as-topology-ext]. If the router that runs
BGP-LS is within one IGP domain and can distinguish passive
interfaces from other interfaces with transit neighbor, it is then
easy for the router to report these passive links using BGP-LS to
centralized PCE controller.
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But OSPF and ISIS have no capabilities to flag such passive
interface.
This document defines the protocol extension for OSPF and ISIS for
the prefix that comes from passive interface.
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. Scenario Description
Figure 1 illustrates the topology scenario when ISIS/OSPF is running
in different domain. B1, B3 are border routers within IGP domain A,
B2, B4 are border routers within domain B. S1-S4 are the internal
routers within domain A, T1-T4 are the internal routers within domain
B. The two domain are interconnected via the links between B1/B2 and
B3/B4.
Passive interfaces are enabled in the links between B1/B2 and B3/B4
respectively. For domain A and B, the S2/T1 router that runs ISIS/
OSPF can't extract the passives links from the normal links and
report it to PCE controller via the BGP-LS protocol. They can only
judge the passive interfaces from other characteristics, such as no
IGP neighbor on this link. Such judgement can extract these passive
links but it is not accurate, because it covers also the situation
when there are some issues to establish the ISIS adjacency/OSPF
neighbor but not the passive interface.
For passive interfaces that are used in the edge router or switches
which connects the server, for example in the router S1/S4 and T2/T4
in Figure 1, knowing these interfaces are correctly configured will
also benefit the management of them.
The method to label these passive interfaces explicitly is necessary
then.
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+-----------------+
+----+IP SDN Controller+----+
| +-----------------+ |
| |
|BGP-LS |BGP-LS
| |
+---------------+-----+ +-----+--------------+
| +--+ +-++ ++-+ +-++ +|-+ +--+|
| |S1+--------+S2+---+B1+-----------+B2+---+T1+--------+T2||
| +-++ N1 +-++ ++-+ +-++ ++++ N2 +-++|
| | | | | || | |
| | | | | || | |
| +-++ +-++ ++-+ +-++ ++++ +-++|
| |S4+--------+S3+---+B3+-----------+B4+---+T3+--------+T4||
| +--+ +--+ ++-+ +-++ ++-+ +--+|
| | | |
| | | |
| Domain A(ISIS) | | Domain B(OSPF) |
+---------------------+ +--------------------+
Figure 1: Inter-AS Domain Scenarios
4. Passive Interface Attribute
4.1. ISIS Passive Interface Attribute
[RFC7794] defines the "IPv4/IPv6 Extended Reachability Attribute
Flags" sub-TLV to advertise the additional flags associated with a
given prefix advertisement. We propose new bit(Bit 5 is desired) to
be assigned by the IANA for the passive interface attribute, as
illustrated in Figure2:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|X|R|N|E|A|U
+-+-+-+-+-+-+-+-+
Figure 2: Prefix Attribute Flags
U-flag: Unactive Flag(Bit 5)
Set for local interface that is configured as passive interface.
When the interfaces on one router be configured as the passive
interface, the U-flag bit will be set in the "IPv4/IPv6 Extended
Reachability Attribute Flags" sub-TLV. This sub-TLV will be included
in the TLV 135, TLV 235, TLV 236 and TLV 237 as necessary and be
flooded within the ISIS domain.
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4.2. OSPF Passive Interface Attribute
[RFC5340] defines the "Prefix Option field" in "Intra-Area-Prefix-
LSAs" LSA to describe the prefix capabilities. The bits in this
field can be defined to flag the prefix is coming from the passive
interface. We propose new bit(Bit 1 is desired) to be assigned by
the IANA for the passive interface, as illustrated in Figure 3:
0 1 2 3 4 5 6 7
+--+--+--+--+--+-+--+--+
| | | U|DN| P|x|LA|NU|
+--+--+--+--+--+-+--+--+
Figure 3: The PrefixOptions Field
U-flag: Unactive Flag(Bit 2)
Set for local interface that is configured as passive interface.
When the interfaces on one router be configured as the passive
interface, the U-flag bit will be set in the "Prefix Option field" of
Intra-Area-Prefix-LSAs.
The router receives such advertisement can then easily distinguish
the passive interfaces from the normal interface, and reports them to
the PCE controller if it run the BGP-LS protocol.
5. Security Considerations
Security concerns for ISIS are addressed in [RFC5304] and[RFC5310]
Advertisement of the additional information defined in this document
introduces no new security concerns.
6. IANA Considerations
IANA is requested to allocate the U-bit (bit position 5 is desired)
from the "Bit Values for Prefix Attribute Flags Sub-TLV" registry of
ISIS TLV codepoint.
IANA is requested to allocate the U-bit(bit position 2 is desired)
from the "OSPFv3 Prefix Options" registry of OSPFv3 Parameters
codepoint.
7. Acknowledgement
Thanks Shunwan Zhang, Tony Li, Les Ginsberg and Robert Raszuk for
their suggestions and comments on this idea.
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8. References
8.1. Normative References
[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>.
[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>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
March 2016, <https://www.rfc-editor.org/info/rfc7794>.
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", draft-ietf-
idr-bgpls-inter-as-topology-ext-08 (work in progress),
April 2020.
Authors' Addresses
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing 102209
China
Email: wangaj3@chinatelecom.cn
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Zhibo Hu
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: huzhibo@huawei.com
Gyan S. Mishra
Verizon Inc.
13101 Columbia Pike
Silver Spring MD 20904
United States of America
Email: gyan.s.mishra@verizon.com
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