Internet DRAFT - draft-gulkohegde-routing-planes-using-sr
draft-gulkohegde-routing-planes-using-sr
SPRING S. Hegde
Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track A. Gulko
Expires: September 14, 2017 Thomson Reuters
March 13, 2017
Separating Routing Planes using Segment Routing
draft-gulkohegde-routing-planes-using-sr-00
Abstract
Many network deployments arrange the network topologies in two or
more planes. The traffic generally uses one of the planes and fails
over to the other plane when there are link or node failure. Certain
applications require the traffic to be strictly restricted to a
particular plane and should not failover to the other plane. This
document proposes a solution for the strict planar routing using
Segment Routing.
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."
This Internet-Draft will expire on September 14, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
Hegde & Gulko Expires September 14, 2017 [Page 1]
Internet-DrafSeparating Routing Planes using Segment Routing March 2017
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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Routing-plane SID . . . . . . . . . . . . . . . . . . . . 3
3.1.1. Elements of procedure . . . . . . . . . . . . . . . . 4
3.2. Multi-topology SID . . . . . . . . . . . . . . . . . . . 4
4. Backward compatibility . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
A3----------------------A4
/ | /|
/ | / |
/ | / |
A1---|-------------------A2 |
| B3------------------|---B4
| / | /
| / | /
| / | /
B1-----------------------B2
Figure 1: Network Planes
The above Figure 1 represents a network topology in two planes.Nodes
A1, A2, A3, A4 are in plane A and B1, B2, B3, B4 are in plane B.
A1->B1, A2->B2, A3->B3, A4->B4 represent the "shunt links" which
connect the two planes. Certain applications require that the
Hegde & Gulko Expires September 14, 2017 [Page 2]
Internet-DrafSeparating Routing Planes using Segment Routing March 2017
traffic follows plane A and remains in plane A in case of failures
and does not cross over to plane B. Strict routing plane
requirements can be met using multiple techniques. This draft
focuses on solutions using Segment Routing technology.
2. Motivation
The motivation of this document is to provide solutions to strict
routing plane requirements using Segment Routing. The following
objectives help to accomplish this in a range of deployment
scenarios.
1. Maintain strict routing within routing planes.
2. Allow traffic to failover within routing plane and do not allow
traffic to failover to other planes
3. Achieve ease of configuration and operational management
3. Solutions
There are multiple ways to address the strict routing plane
requirements. Section 3.1 describes a mechanism by using diferrent
SIDs for each plane.Another option is to use Multi-topology SIDs as
defined in Section 3.2.
3.1. Routing-plane SID
A new SID called Routing-Plane SID is defined and associated with new
algorithm values. This document proposes 4 new algorithm values
which represent SPF in routing-planes. When the network topology is
organized into two different planes, each node in plane A associates
a new Routing-Plane SID to one of it's loopback addresses and
advertises the SID in the segment routing extension defined in [SR-
OSPF] section 2.1 and [SR-IS-IS] section 5. The prefix-SID sub-TLV
carries the new algorithm values corresponding to the routing-plane.
The traffic which needs to be restricted to a certain routing-
plane,should use the Routing-Plane SID corresponding to that plane to
forward the traffic. The paths through the Routing planes MAY use
single Routing Plane SID or a stack of multiple Routing Plane SIDs.
Adjacency-SIDs can also be used build paths across routing planes.
Adjacency-SIDs are not scoped per-algorithm and it is possible that
the protection path for the adjacency SIDs uses a path going over a
different routing-plane.It is recommended to use non-protected
adjacency-SIDs to avoid backup traffic flowing through different
plane.
Hegde & Gulko Expires September 14, 2017 [Page 3]
Internet-DrafSeparating Routing Planes using Segment Routing March 2017
3.1.1. Elements of procedure
All the nodes that belong to a certain routing-plane MUST advertise
the algorithm corresponding to that routing-plane in the algorithm
sub-TLV as defined in [SR-OSPF] and [SR-IS-IS]. The nodes SHOULD
also advertise Routing-Plane SID corresponding to that algorithm in
the prefix-SID Sub-TLV.
A node that receives the algorithm sub-TLV with new algorithm value
specified in Section 6 MUST compute SPF with all the nodes that
advertised the new algorithm. The next-hops and RIB entries for the
Routing-Plane SIDs MUST be computed from the routing-plane SPF.
Certain nodes MAY belong to multiple routing-planes. Such nodes MUST
compute SPF corresponding to each plane and compute the next-hops for
the SIDs corresponding to each plane.
Each router MAY assign different IP address corresponding to each
plane or MAY use the same IP address to assign the node-SIDs and
Routing-Plane SIDs. The ingress routers MAY advertise binding-SIDs
as defined in [SR-ARCH]section 3.5.2, for the label stacks that are
constructed using routing-Plane SIDs. The ingress routers MAY map
the incoming IP traffic onto the Routing-Plane SIDs, the mechanisms
to do so is implementation dependant and outside the scope of this
document.
When the network topology is organized into multiple IGP levels or
areas, the Routing Plane SIDs MAY be re-originated from one IGP
domain into the other domain by the border routers. The border IGP
routers MUST re-advertise the Routing-Plane SIDs if they belong to
the corresponding Routing plane and has advertised the algorithm
corresponding to the routing-plane.
3.2. Multi-topology SID
Multi topology Routing defines mechanisms to support multiple
topologies in a single physical network. ISIS and OSPF extensions to
support multi-topology routing is defined in [RFC5120] and [RFC4915]
respectively. Multi-topology routing defined in [RFC5120] and
[RFC4915] describes mechanisms to separate topologies in ISIS and
OSPF by advertising separate MT-TLVs in ISIS and multi-topology
scoped Router LSA in OSPF. The different routing planes in customer
network can be assigned with different MT-ID for each routing-plane
and the multi-topology SIDs can be advertised for each MT-ID as
described in [SR-OSPF] and [SR-IS-IS]. Multi-topology SIDs are
associated with algorithm 0 and no new algorithm definition is
required. All the nodes in the network MUST also support multi-
topology routing as defined in [RFC5120] and [RFC4915]. All the
nodes in the network compute separate SPF per MT-ID and program the
Hegde & Gulko Expires September 14, 2017 [Page 4]
Internet-DrafSeparating Routing Planes using Segment Routing March 2017
forwarding planes with MT-SIDs accordingly. Multi-topology SIDs are
used to build the explicit paths through the network. Multi-topology
based solution has an advantage of possibility of assigning different
IGP costs to links for different MTs. For deployments that do not
need separate IGP costs and topologies for each routing plane, it
comes with an additional operational overhead of maintaining multi-
topology configurations.
4. Backward compatibility
The mechanism described in the document is fully backward compatible.
If a node does not support the extensions defined in this document,
it will not advertise the additional algorithm values in the
algorithm sub-TLV. All the computing nodes will not consider the
node in the SPF computation if it has not advertised the specific
algorithm. For the multi-topology based solution backward
compatibility mechanism described in [RFC5120] and [RFC4915] are
applicable.
5. Security Considerations
This document does not introduce any further security issues other
than those discussed in [SR-OSPF] and [SR-IS-IS].
6. IANA Considerations
This specification updates OSPF and ISIS registry:
OSPF Router Information (RI) TLVs Registry
8 (IANA Preallocated) - SR-Algorithm TLV
Algorithm 2 -5 : SPF in routing plane
ISIS Sub TLVs for Type 242
Type: TBD (suggested value 19)
Description: Segment Routing Algorithm
Algorithm 2-5 : SPF in Routing Plane
7. Acknowledgements
Hegde & Gulko Expires September 14, 2017 [Page 5]
Internet-DrafSeparating Routing Planes using Segment Routing March 2017
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,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<http://www.rfc-editor.org/info/rfc4915>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<http://www.rfc-editor.org/info/rfc5120>.
[SR-IS-IS]
"IS-IS Extensions for Segment Routing, draft-ietf-isis-
segment-routing-extensions-11(work in progress)", October
2016.
[SR-OSPF] "OSPF Extensions for Segment Routing, draft-ietf-ospf-
segment-routing-extensions-11(work in progress)", July
2016.
[SR-OSPFv3]
"OSPFv3 Extensions for Segment Routing, draft-ietf-ospf-
ospfv3-segment-routing-extensions-06(work in progress)",
July 2016.
8.2. Informative References
[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, <http://www.rfc-editor.org/info/rfc7684>.
[SR-ARCH] "Segment Routing Architecture, draft-ietf-spring-segment-
routing-09(work in progress)", July 2016.
Hegde & Gulko Expires September 14, 2017 [Page 6]
Internet-DrafSeparating Routing Planes using Segment Routing March 2017
Authors' Addresses
Shraddha Hegde
Juniper Networks, Inc.
Embassy Business Park
Bangalore, KA 560093
India
Email: shraddha@juniper.net
Arkadiy Gulko
Thomson Reuters
Email: arkadiy.gulko@thomsonreuters.com
Hegde & Gulko Expires September 14, 2017 [Page 7]
