| Networking Working Group | L. Ginsberg |
| Internet-Draft | A. Bashandy |
| Intended status: Standards Track | C. Filsfils |
| Expires: February 24, 2017 | S. Previdi |
| Cisco Systems | |
| M. Nanduri | |
| Microsoft | |
| E. Aries | |
| Private Contributer | |
| August 23, 2016 |
Advertising L2 Bundle Member Link Attributes in IS-IS
draft-ietf-isis-l2bundles-02.txt
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.
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].
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/.
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This Internet-Draft will expire on February 24, 2017.
Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved.
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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.
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.
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:
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.
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:
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.
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.
[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 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.
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
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.
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
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
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.
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.
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
None.
The authors would like to thank Jon MItchell for his careful review.
| [RFC4655] | Farrel, A., Vasseur, J. and J. Ash, A Path Computation Element (PCE)-Based Architecture", RFC 4655, DOI 10.17487/RFC4655, August 2006. |
| [SR] | IS-IS Extensions for Segment Routing, draft-ietf-isis-segment-routing-extensions-07(work in progress)", June 2016. | , "
| [SR-ARCH] | Segment Routing Architecture, draft-ietf-spring-segment-routing-09(work in progress)", July 2016. | , "