Internet DRAFT - draft-ginsberg-isis-l2bundles
draft-ginsberg-isis-l2bundles
Networking Working Group L. Ginsberg
Internet-Draft A. Bashandy
Intended status: Standards Track C. Filsfils
Expires: August 19, 2016 S. Previdi
Cisco Systems
M. Nanduri
Microsoft
E. Aries
Private Contributer
February 16, 2016
Advertising L2 Bundle Member Link Attributes in IS-IS
draft-ginsberg-isis-l2bundles-02.txt
Abstract
There are deployments where the Layer 3 interface on which IS-IS
operates is a Layer 2 interface bundle. Existing IS-IS
advertisements only support advertising link attributes of the Layer
3 interface. If entities external to IS-IS wish to control traffic
flows on the individual physical links which comprise the Layer 2
interface bundle link attribute information about the bundle members
is required.
This document introduces the ability for IS-IS to advertise the link
attributes of layer 2 (L2) bundle members.
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.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on August 19, 2016.
Copyright Notice
Copyright (c) 2016 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
(http://trustee.ietf.org/license-info) in effect on the date of
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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. L2 Bundle Member Attributes TLV . . . . . . . . . . . . . . . 3
2.1. Parallel L3 Adjacencies . . . . . . . . . . . . . . . . . 5
2.2. Shared Attribute sub-TLVs . . . . . . . . . . . . . . . . 5
3. Advertising L2 Bundle Member Adj-SIDs . . . . . . . . . . . . 5
3.1. L2 Bundle Member Adjacency Segment Identifier sub-TLV . . 6
3.2. L2 Bundle Member LAN Adjacency Segment Identifier sub-TLV 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . 11
7.2. Informational References . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
There are deployments where the Layer 3 interface on which an IS-IS
adjacency is established is a Layer 2 interface bundle, for instance
a Link Aggregation Group (LAG) [IEEE802.1AX]. This reduces the
number of adjacencies which need to be maintained by the routing
protocol in cases where there are parallel links between the
neighbors. Entities external to IS-IS such as Path Computation
Elements (PCE) [RFC4655] may wish to control traffic flows on
individual members of the underlying Layer 2 bundle. In order to do
so link attribute information about individual bundle members is
required - but currently IS-IS only supports advertising link
attributes for the Layer 3 interfaces on which it operates.
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This document introduces a new TLV to advertise link attribute
information for each of the L2 bundle members which comprise the
Layer 3 interface on which IS-IS operates.
[SR] introduces a new link attribute - adjacency segment identifier
(Adj-SID) - which can be used as an instruction to forwarding to send
traffic over a specific link. This document introduces additional
sub-TLVs to advertise Adj-SIDs for L2 Bundle members.
Note that the new advertisements defined in this document are
intended to be provided to external entities.
2. L2 Bundle Member Attributes TLV
A new TLV is introduced to advertise L2 Bundle member attributes.
Although much of the information is identical to and uses the same
sub-TLVs included in Extended IS-Neighbor advertisements (TLVs 22 and
222), a new TLV is used so that changes to the advertisement of the
L2 Bundle member link attributes does not trigger unnecessary action
by the [ISO10589] Decision process.
This new TLV utilizes the sub-TLV space defined for TLVs 22, 23, 141,
222, and 223.
The following new TLV is introduced:
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L2 Bundle Member Attributes
Type: 25 (suggested - to be assigned by IANA)
Length: Number of octets to follow
Parent L3 Neighbor Descriptor
L3 Neighbor System ID + pseudonode ID (7 octets)
Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|P| |
+-+-+-+-+-+-+-+-+
where:
P-flag: When set to 1 one of the sub-TLVs described
in Section 2.1 immediately follows the flags field.
If the P-flag is set to 0, then none of the sub-TLVs
described in Section 2.1 are present.
Other bits: MUST be zero when originated and ignored when
received.
One or more of the following:
L2 Bundle Attribute Descriptors
Length of L2 Bundle Attribute Descriptor (1 octet)
NOTE: This includes all fields described below.
Number of L2 Bundle Member Descriptors (1 octet)
L2 Bundle Member Link Local Identifiers
(4 * Number of L2 Bundle Member Descriptors octets)
NOTE: An L2 Bundle Member Descriptor is a Link Local
Identifier as defined in [RFC5307].
sub-TLV(s)
A sub-TLV may define an attribute common to all of
the bundle members listed or a sub-TLV may define an
attribute unique to each bundle member. Use of these
two classes of sub-TLVs is described in the following
sections.
NOTE: Only one Parent L3 Neighbor Descriptor is present in a given
TLV. Multiple L2 Bundle Attribute Descriptors may be present in a
single TLV.
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2.1. Parallel L3 Adjacencies
When there exist multiple L3 adjacencies to the same neighbor
additional information is required to uniquely identify the L3
Neighbor. One and only one of the following three sub-TLVs is used
to uniquely identify the L3 adjacency:
o IPv4 Interface Address (sub-TLV 6 defined in [RFC5305])
o IPv6 Interface Address (sub-TLV 12 defined in [RFC6119])
o Link Local/Remote Identifiers (sub-TLV 4 defined in [RFC5307])
When the P-bit is set in the flags field in the Parent L3 Neighbor
Descriptor one and only one of the above sub-TLVs MUST be present.
The chosen sub-TLV MUST immediately follow the flags field described
in Section 2.
These sub-TLVs MAY be omitted if no parallel adjacencies to the
neighbor exist.
2.2. Shared Attribute sub-TLVs
These sub-TLVs advertise a single copy of an attribute (e.g. link
bandwidth). The attribute applies to all of the L2 Bundle Members in
the set advertised under the preceding L2 Bundle Member Attribute
Descriptor. No more than one copy of a given sub-TLV in this
category may appear in the set of sub-TLVs under the preceding L2
Bundle Member Attribute Descriptor. If multiple copies of a given
sub-TLV are present both MUST be ignored.
The set of L2 Bundle Member Descriptors which may be advertised under
a single L2 Bundle Member Attribute Descriptor is therefore limited
to bundle members which share the set of attributes advertised in the
shared attribute sub-TLVs.
All existing sub-TLVs defined in the IANA Sub-TLVs for TLVs 22, 23,
141, 222, and 223 registry are in the category of shared attribute
sub-TLVs unless otherwise specified in this document.
3. Advertising L2 Bundle Member Adj-SIDs
[SR] defines sub-TLVs to advertise Adj-SIDs for L3 adjacencies.
However these sub-TLVs only support a advertisement of a single Adj-
SID. As it is expected that each L2 Bundle member will have unique
Adj-SIDs in many deployments it is desirable to define a new sub-TLV
which allows more efficient encoding of a set of Adj-SIDs in a single
sub-TLV. Two new sub-TLVs are therefore introduced to support
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advertising Adj-SIDs for L2 Bundle members. The format of the new
sub-TLVs is similar to that used for L3 adjacencies, but is optimized
to allow advertisement of a set of Adj-SIDs (one per L2 Bundle
Member) in a single sub-TLV.
The two new sub-TLVs defined in the following sections do not fall
into the category of shared attribute sub-TLVs.
3.1. L2 Bundle Member Adjacency Segment Identifier sub-TLV
This sub-TLV is used to advertise Adj-SIDs for L2 Bundle Members
associated with a parent L3 adjacency which is Point-to-Point. The
following format is defined for this sub-TLV:
Type: 41 (suggested value to be assigned by IANA) (1 octet)
Length: variable (1 octet)
Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|F|*|V|L|S| |
+-+-+-+-+-+-+-+-+
where:
* - Is a flag used in the L3 Adj-SID sub-TLV but which is NOT
used in this sub-TLV. These bits SHOULD be sent as 0 and MUST
be ignored on receipt
F-Flag: Address-Family flag. If unset, then the Adj-SID refers
to an L2 Bundle Member with outgoing IPv4 encapsulation. If set
then the Adj-SID refers to an L2 Bundle Member with outgoing
IPv6 encapsulation.
V-Flag: Value flag. If set, then the Adj-SID carries a value.
By default the flag is SET.
L-Flag: Local Flag. If set, then the value/index carried by
the Adj-SID has local significance. By default the flag is
SET.
S-Flag. Set Flag. When set, the S-Flag indicates that the
Adj-SID refers to a set of L2 Bundle Members (and therefore
MAY be assigned to other L2 Bundle Members as well).
Other bits: MUST be zero when originated and ignored when
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received.
Weight: 1 octet. The value represents the weight of the Adj-SID
for the purpose of load balancing. The use of the weight is
defined in [SR-ARCH].
NOTE: Flags and weight are shared by all L2 Bundle Members
listed in the L2 Bundle Attribute Descriptor.
L2 Bundle Member Adj-SID Descriptors. There MUST be one descriptor
for each of the L2 Bundle Members advertised under the preceding
L2 Bundle Member Attribute Descriptor. Each descriptor consists
of one of the following fields:
SID/Index/Label: according to the V and L flags, it contains
either:
* A 3 octet local label where the 20 rightmost bits are used
for encoding the label value. In this case the V and L
flags MUST be set.
* A 4 octet index defining the offset in the SID/Label space
advertised by this router. See [SR].
In this case V and L flags MUST be unset.
* A 16 octet IPv6 address. In this case the V flag MUST be
set. The L flag MUST be unset if the IPv6 address is
globally unique.
3.2. L2 Bundle Member LAN Adjacency Segment Identifier sub-TLV
This sub-TLV is used to advertise Adj-SIDs for L2 Bundle Members
associated with a parent L3 adjacency which is a LAN adjacency. In
LAN subnetworks, the Designated Intermediate System (DIS) is elected
and originates the Pseudonode-LSP (PN-LSP) including all neighbors of
the DIS. When Segment Routing is used, each router in the LAN MAY
advertise the Adj-SID of each of its neighbors on the LAN.
Similarly, for each L2 Bundle Member a router MAY advertise an Adj-
SID to each neighbor on the LAN.
The following format is defined for this sub-TLV:
Type: 42 (suggested value to be assigned by IANA) (1 octet)
Length: variable (1 octet)
Neighbor System ID: 6 octets
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Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|F|*|V|L|S| |
+-+-+-+-+-+-+-+-+
where:
* - Is a flag used in the L3 Adj-SID sub-TLV but which is NOT
used in this sub-TLV. These bits SHOULD be sent as 0 and MUST
be ignored on receipt
F-Flag: Address-Family flag. If unset, then the Adj-SID refers
to an L2 Bundle Member with outgoing IPv4 encapsulation. If set
then the Adj-SID refers to an L2 Bundle Member with outgoing
IPv6 encapsulation.
V-Flag: Value flag. If set, then the Adj-SID carries a value.
By default the flag is SET.
L-Flag: Local Flag. If set, then the value/index carried by
the Adj-SID has local significance. By default the flag is
SET.
S-Flag. Set Flag. When set, the S-Flag indicates that the
Adj-SID refers to a set of L2 Bundle Members (and therefore
MAY be assigned to other L2 Bundle Members as well).
Other bits: MUST be zero when originated and ignored when
received.
Weight: 1 octet. The value represents the weight of the Adj-SID
for the purpose of load balancing. The use of the weight is
defined in [SR-ARCH].
NOTE: Flags and weight are shared by all L2 Bundle Members
listed in the L2 Bundle Attribute Descriptor.
L2 Bundle Member LAN Adj-SID Descriptors. There MUST be one
descriptor for each of the L2 Bundle Members advertised
under the preceding L2 Bundle Member Attribute Descriptor.
Each descriptor consists of one of the following fields:
SID/Index/Label: according to the V and L flags, it contains
either:
* A 3 octet local label where the 20 rightmost bits are used
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for encoding the label value. In this case the V and L
flags MUST be set.
* A 4 octet index defining the offset in the SID/Label space
advertised by this router. See [SR].
In this case V and L flags MUST be unset.
* A 16 octet IPv6 address. In this case the V flag MUST be
set. The L flag MUST be unset if the IPv6 address is
globally unique.
4. IANA Considerations
This document adds the following new TLV to the IS-IS TLV Codepoints
registry.
Value: 25 (suggested - to be assigned by IANA)
Name: L2 Bundle Member Attributes
The name of the Sub-TLVs for TLVs 22, 23, 141, 222, and 223 registry
needs to be changed to Sub-TLVs for TLVs 22, 23, 25, 141, 222, and
223 registry. An additional column needs to be added to the registry
to indicate which sub-TLVs may appear in the new L2 Bundle Member
Attributes TLV. The following table indicates the appropriate
settings for all currently defined sub-TLVs as regards their use in
the new L2 Bundle Member Attributes TLV.
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3 Administrative group (color) y
4 Link Local/Remote Identifiers y
6 IPv4 interface address y
8 IPv4 neighbor address y
9 Maximum link bandwidth y
10 Maximum reservable link bandwidth y
11 Unreserved bandwidth y
12 IPv6 Interface Address y
13 IPv6 Neighbor Address y
14 Extended Administrative Group y
18 TE Default metric y
19 Link-attributes y
20 Link Protection Type y
21 Interface Switching Capability Descriptor y
22 Bandwidth Constraints y
23 Unconstrained TE LSP Count y
24 Remote AS number n
25 IPv4 remote ASBR Identifier n
26 IPv6 remote ASBR Identifier n
27 Interface Adjustment Capability Descriptor (IACD) y
28 MTU n
29 SPB-Metric y
30 SPB-A-OALG y
This document adds the following new sub-TLVs to the sub-TLVs for
TLVs 22, 23, 25, 141, 222, and 223 registry.
Value: 41 (suggested - to be assigned by IANA)
Name: L2 Bundle Member Adj-SID
This sub-TLV is allowed in the following TLVs:
22 23 25 141 222 223
n n y n n n
Value: 42 (suggested to be assigned by IANA)
Name: L2 Bundle Member LAN Adj-SID
This sub-TLV is allowed in the following TLVs:
22 23 25 141 222 223
n n y n n n
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5. Security Considerations
None.
6. Acknowledgements
The authors would like to thank Jon MItchell for his careful review.
7. References
7.1. Normative References
[IEEE802.1AX]
Institute of Electrical and Electronics Engineers, "IEEE
Standard for Local and Metropolitan Area Networks - Link
Aggregation.", ISO/IEC 10589:2002, Second Edition, Nov
2008.
[ISO10589]
International Organization for Standardization,
"Intermediate system to Intermediate system intra-domain
routeing information exchange protocol for use in
conjunction with the protocol for providing the
connectionless-mode Network Service (ISO 8473)", ISO/
IEC 10589:2002, Second Edition, Nov 2002.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <http://www.rfc-editor.org/info/rfc5305>.
[RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
<http://www.rfc-editor.org/info/rfc5307>.
[RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119,
February 2011, <http://www.rfc-editor.org/info/rfc6119>.
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7.2. Informational References
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<http://www.rfc-editor.org/info/rfc4655>.
[SR] "IS-IS Extensions for Segment Routing, draft-ietf-isis-
segment-routing-extensions-06(work in progress)", December
2015.
[SR-ARCH] "Segment Routing Architecture, draft-ietf-spring-segment-
routing-07(work in progress)", December 2015.
Authors' Addresses
Les Ginsberg
Cisco Systems
510 McCarthy Blvd.
Milpitas, CA 95035
USA
Email: ginsberg@cisco.com
Ahmed Bashandy
Cisco Systems
170 West Tasman Drive
San Jose, Ca 95134
US
Clarence Filsfils
Cisco Systems
Email: cf@cisco.com
Stefano Previdi
Cisco Systems
Via Del Serafico 200
Rome 0144
Italy
Email: sprevidi@cisco.com
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Mohan Nanduri
Microsoft
Email: mnanduri@microsft.com
Ebben Aries
Private Contributer
Email: exa@dscp.org
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