Network Working Group N. Wu
Internet-Draft Z. Zhuang
Intended status: Standards Track Huawei
Expires: April 21, 2016 October 19, 2015
BGP Extensions for Segment Allocation
draft-wu-idr-bgp-segment-allocation-ext-00
Abstract
This document defines extensions to the BGP-LS to distribute/push the
segment information to its administrative SR domain and describes
some use cases.
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
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 21, 2016.
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document authors. All rights reserved.
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Provisions Relating to IETF Documents
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Allocating Segment in BGP Networks . . . . . . . . . . . 3
3.2. Allocating Segment in IGP Networks . . . . . . . . . . . 3
4. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 3
4.1. Node NLRI for Segment Allocation . . . . . . . . . . . . 3
4.2. Link NLRI for Segment Allocation . . . . . . . . . . . . 4
4.3. Prefix NLRI for Segment Allocation . . . . . . . . . . . 5
5. Applications . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Allocating Segments for BGP Networks . . . . . . . . . . 6
5.1.1. Node-SID Distribution via a Prefix NLRI . . . . . . . 7
5.1.2. Adj-SID Distribution via a Link NLRI . . . . . . . . 7
5.2. Allocating Segments for IGP Networks . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
In those networks with a central controller, it may be beneficial to
allocate and manage SIDs for the network since the controller has the
whole link-state database in mind. This document proposes BGP
extensions to allocate SIDs in a centralized manner instead of
distribution way.
2. Terminology
o MPP: MPLS Path Programming
o RR: Route Reflector
o SID: Segment Identifier
o SR-Path: Segment Routing Path
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3. Motivation
3.1. Allocating Segment in BGP Networks
It is possible that BGP may be the only routing protocol in some
networks, such as the one described in
[I-D.ietf-rtgwg-bgp-routing-large-dc]. If Segment Routing
[I-D.ietf-spring-segment-routing] is going to be used for in the
dataplane, it will be better to allocate SIDs in a centralized manner
since no IGP flooding mechanism to advertise now.
In order to allocating SIDs, the centralized allocator SHOULD collect
BGP network topology database ahead, which at least consists of BGP
speakers, prefixes and adjacencies among them. No concrete technique
for collecting this database has been specified in this document.
3.2. Allocating Segment in IGP Networks
In the scenario SR & LDP interoperation described in
[I-D.ietf-spring-segment-routing-ldp-interop], if mapping entries are
allocated in a centralized manner, e.g. a controller, it is possible
that Binding SIDs will be populated to a designated SRMS through a
protocol instead of IGP, no matter whether the SRMS is a dedicated
server or function module.
4. Protocol Extensions
This section defines a new Protocol-ID called as BGP-Segment-
Allocation (TBA) in the BGP-LS specification. The use of a new
Protocol-ID allows separation and differentiation between the NLRIs
carrying Segment Allocation information from the NLRIs carrying IGP
link-state information as defined in [I-D.ietf-idr-ls-distribution].
4.1. Node NLRI for Segment Allocation
This section describes the Node NLRI used for allocating the Node-
SID. The Node NLRI Type uses descriptors and attributes already
defined in [I-D.ietf-idr-ls-distribution]. The format of the Node
NLRI Type is as follows:
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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
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local Node Descriptors //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
o Protocol-ID set to the new Protocol-ID: BGP-Segment-Allocation
o Node Descriptors defined in [I-D.ietf-idr-ls-distribution] can be
reused
This NLRI MAY contain BGP-LS-SR TLV 1033 (SID/Label Binding) as its
attribute.
4.2. Link NLRI for Segment Allocation
This section describes the Link NLRI used for allocating the Adj-SID.
The format of the Link NLRI Type is as follows:
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
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local Node Descriptors //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Remote Node Descriptors //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Link Descriptors //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
o Protocol-ID set to the new Protocol-ID: BGP-Segment-Allocation
o Node Descriptors and Link Descriptors defined in
[I-D.ietf-idr-ls-distribution] can be reused.
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Following TLV will be used in Link Attribute:
o BGP-LS-SR TLV 1034: SR Capabilities
o BGP-LS-SR TLV 1035: SR Algorithm
o BGP-LS-SR TLV 1099: Adj-SID
o BGP-LS-SR TLV 1036: Peer-SID
o BGP-LS-SR TLV 1037: Peer-Set-SID
4.3. Prefix NLRI for Segment Allocation
This section describes the Prefix NLRI used for Allocating the
Prefix-SID. The format of the Link NLRI Type is as follows:
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
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local Node Descriptors //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Prefix Descriptors //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
o Protocol-ID set to the new Protocol-ID: BGP-Segment-Allocation
o Node Descriptors and Prefix Descriptors defined in
[I-D.ietf-idr-ls-distribution] can be reused.
Following TLV will be used in Prefix Attribute:
o BGP-LS-SR TLV 1034: SR Capabilities
o BGP-LS-SR TLV 1035: SR Algorithm
o BGP-LS-SR TLV 1158: Prefix SID
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5. Applications
5.1. Allocating Segments for BGP Networks
As shown below, we assume:
Each node is its own AS (Node X has AS X). The loopback of Node X is
1.1.1.x/32.
Each node peers with its neighbors via BGP session.
Each node peers with Controller via BGP session.
Local BGP-LS Identifier in Node X is set to X0000.
/----------\
| |
| Controller |
| |
\----------/
|
+-----------------------+-------------------------------+
| | |
| +------+ | +------+ |
| | N7 |-+-| N8 | Tier-1 |
| +------+ +------+ |
| | | | | |
| +---------+ | | +----------+ |
| | +-------+--+-------+--+-------+ | |
| | | | | | | | | |
| +----+ +----+ +----+ +----+ |
| | N3 |-----| N4 | | N5 |-----| N6 | Tier-2 |
| +----+ +----+ +----+ +----+ |
| | | | | |
| | +-----+ | | +-----+ | |
| +-| N1 |-+ +-| N2 |-+ Tier-3 |
| +-----+ +-----+ |
| | | | | | | |
| <- Servers -> <- Servers -> |
+-------------------------------------------------------+
When the controller has collected the topology information of this
BGP network, it can start segment allocation to the network.
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5.1.1. Node-SID Distribution via a Prefix NLRI
A Node-SID represents a Node and has a global significance, something
like a loopback of a router. Like an operator assigns a loopback's
to their routers, it's expected that the Node-SID value will be
assigned to every node. The assigned value can be an absolute or
Index value and must be globally unique. In order to push a Node-SID
for a router(e.g., N7), Controller advertise a Prefix NLRI to all the
routers of the BGP-SR Network, where:
o Protocol-ID set to the new Protocol-ID: BGP-Segment-Allocation
o Local Node Descriptors contains
* BGP Router-ID: 7.7.7.7
* Local ASN: AS7
* BGP-LS Identifier: 70000
o Prefix Descriptors
* 7.7.7.7/32
o Prefix Attribute contains
* BGP-LS-SR TLV 1034: SR Capabilities
* BGP-LS-SR TLV 1035: SR Algorithm
* BGP-LS-SR TLV 1158: Prefix SID, With the N-flag (node-SID flag)
set.
* Other Prefix Attributes.
5.1.2. Adj-SID Distribution via a Link NLRI
In order to push a Adj-SID for a router(e.g., N7 connects to N8),
Controller advertise a Link NLRI to all the routers of the BGP-SR
Network, where:
o Protocol-ID set to the new Protocol-ID: BGP-Segment-Allocation
o Local Node Descriptors contains
* BGP Router-ID: 7.7.7.7
* Local ASN: AS7
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* BGP-LS Identifier: 70000
o Remote Node Descriptors contains
* BGP Router-ID: 8.8.8.8
* Local ASN: AS8
* BGP-LS Identifier: 80000
o Link Descriptors
* BGP session IPv4 local address: 7.7.7.7
* BGP session IPv4 peer address: 8.8.8.8
o Link Attribute contains
* BGP-LS-SR TLV 1034: SR Capabilities
* BGP-LS-SR TLV 1035: SR Algorithm
* BGP-LS-EPE TLV 1036: Peer-Node-SID
* Other Prefix Attributes.
In the similar way, the controller can distribute Peer-Adj-SID and
Peer-Set-SID.
5.2. Allocating Segments for IGP Networks
In IGP networks deployed with SR, the method defined in
[I-D.ietf-idr-ls-distribution] to populate the topology database and
the SRGB to the controller.
A controller may use the extensions defined in this document to
populate mapping entries to the SRMS. Then the SRMS will advertise
this mapping to all the SR Nodes via IGP.
In the following figure, LSR1-10 and LSR20 are only running LDP and
R21-to-R25 Routers are SR capable Routers. R21 and R22 will be
running both SR and LDP as they are on the border between SR and LDP.
The whole network is running single IGP let's say IS-IS.
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/----------\
| |
| Controller |
| |
\----------/
/ \
/ \
+----------------------------+----------/-------\---------------+
| LDP Domain | /SR Domain\ |
| | / \ |
| ------ ------- / ------ \ --------- |
| |LSR1|\ | R21 |---+----| R23|\----\|Mapping| |
| ------ \ /-------\ / ------\ |Server | |
| 10.1.1.1\ / 20.1.1.1\ / 20.1.1.3\ --------+ |
| \ / | \ / \ 30.1.1.1 |
| ------ \ ------- / | \/ \ ------ |
| |LSR2|-----\|LSR20|/ | /\ \| R25| |
| ------ / -------\ | / \ /------ |
| 10.1.1.2 / 10.1.1.20\ | / \ / 20.1.1.5 |
| ... / \ | / \ / |
| ------ / \-------/ \------ / |
||LSR10|/ | R22 |----------|R24 |/ |
| ------ ------- ------ |
| 10.1.1.10 20.1.1.2 20.1.1.4 |
| | |
| | |
+----------------------------+----------------------------------+
The Node-SIDs and their corresponding label value mapping could be
like this:
Prefix Index Value Range
------------------------------------
10.1.1.1/32 1001 10
10.1.1.20/32 1020 1
20.1.1.1/32 2001 5
The controller will advertise a node NLRI to Mapping Server, where:
o Protocol-ID set to the new Protocol-ID: BGP-Segment-Allocation
o Local Node Descriptors contains
* Mapping Server's node descriptor
o Node Attribute contains
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* BGP-LS-SR TLV-1033: SID/Label Binding TLV
* Other Prefix Attributes
Mapping Server will convert BGP-LS-SR TLV-1033 to IS-IS TLV-149, and
advertise this mapping to all the SR Nodes via IS-IS.
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 |0|0| | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Range = 10 | /32 | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .1 | .1 | .1 |Prefix-SID Type|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLV Length| Flags | Algorithm | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |0|0| | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Range = 1 | /32 | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .1 | .1 | .20 |Prefix-SID Type|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLV Length| Flags | Algorithm | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |0|0| | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Range = 5 | /32 | 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .1 | .1 | .1 |Prefix-SID Type|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLV Length| Flags | Algorithm | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A node receiving a MS entry for a prefix MUST check the existence of
such prefix in its link-state database prior to consider and use the
associated SID. This has been defined in
[I-D.ietf-isis-segment-routing-extensions].
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6. IANA Considerations
TBD.
7. Security Considerations
TBD.
8. Acknowledgements
TBD.
9. References
9.1. Normative References
[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
Ray, "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution-13
(work in progress), October 2015.
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
Extensions for Segment Routing", draft-ietf-isis-segment-
routing-extensions-05 (work in progress), June 2015.
[I-D.ietf-rtgwg-bgp-routing-large-dc]
Lapukhov, P., Premji, A., and J. Mitchell, "Use of BGP for
routing in large-scale data centers", draft-ietf-rtgwg-
bgp-routing-large-dc-07 (work in progress), August 2015.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and r. rjs@rob.sh, "Segment Routing Architecture", draft-
ietf-spring-segment-routing-06 (work in progress), October
2015.
[I-D.ietf-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and
S. Litkowski, "Segment Routing interoperability with LDP",
draft-ietf-spring-segment-routing-ldp-interop-00 (work in
progress), October 2015.
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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,
<http://www.rfc-editor.org/info/rfc2119>.
9.2. Informative References
[I-D.gredler-idr-bgp-ls-segment-routing-extension]
Gredler, H., Ray, S., Previdi, S., Filsfils, C., Chen, M.,
and J. Tantsura, "BGP Link-State extensions for Segment
Routing", draft-gredler-idr-bgp-ls-segment-routing-
extension-02 (work in progress), October 2014.
[I-D.ietf-idr-bgpls-segment-routing-epe]
Previdi, S., Filsfils, C., Ray, S., Patel, K., Dong, J.,
and M. Chen, "Segment Routing Egress Peer Engineering BGP-
LS Extensions", draft-ietf-idr-bgpls-segment-routing-
epe-00 (work in progress), June 2015.
Authors' Addresses
Nan Wu
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: eric.wu@huawei.com
Shunwan Zhuang
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: zhuangshunwan@huawei.com
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