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Open Shortest Path First IGP S. Hegde Open Shortest Path First IGP S. Hegde
Internet-Draft Juniper Networks, Inc. Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track R. Shakir Intended status: Standards Track R. Shakir
Expires: April 11, 2016 Individual Expires: April 18, 2016 Individual
A. Smirnov A. Smirnov
Cisco Systems, Inc. Cisco Systems, Inc.
Z. Li Z. Li
Huawei Technologies Huawei Technologies
B. Decraene B. Decraene
Orange Orange
October 9, 2015 October 16, 2015
Advertising per-node administrative tags in OSPF Advertising per-node administrative tags in OSPF
draft-ietf-ospf-node-admin-tag-07 draft-ietf-ospf-node-admin-tag-08
Abstract Abstract
This document describes an extension to OSPF protocol to add an This document describes an extension to the OSPF protocol to add an
optional operational capability, that allows tagging and grouping of optional operational capability, that allows tagging and grouping of
the nodes in an OSPF domain. This allows simplification, ease of the nodes in an OSPF domain. This allows simplification, ease of
management and control over route and path selection based on management and control over route and path selection based on
configured policies. This document describes an extension to OSPF configured policies. This document describes an extension to the
protocol to advertise per-node administrative tags. The node-tags OSPF protocol to advertise per-node administrative tags. The node-
can be used to express and apply locally-defined network policies tags can be used to express and apply locally-defined network
which is a very useful operational capability. Node tags may be used policies which is a very useful operational capability. Node tags
either by OSPF itself or by other applications consuming information may be used either by OSPF itself or by other applications consuming
propagated via OSPF. information propagated via OSPF.
This document describes the protocol extensions to disseminate per- This document describes the protocol extensions to disseminate per-
node administrative-tags to the OSPFv2 and OSPFv3 protocol. It node administrative tags to the OSPFv2 and OSPFv3 protocol. It
provides example use cases of administrative node tags. provides example use cases of administrative node tags.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo Status of This Memo
skipping to change at page 2, line 10 skipping to change at page 2, line 10
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 11, 2016. This Internet-Draft will expire on April 18, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Administrative Tag TLV . . . . . . . . . . . . . . . . . . . 3 2. Administrative Tag TLV . . . . . . . . . . . . . . . . . . . 3
3. OSPF per-node administrative tag TLV . . . . . . . . . . . . 3 3. OSPF per-node administrative tag TLV . . . . . . . . . . . . 3
3.1. TLV format . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. TLV format . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Elements of procedure . . . . . . . . . . . . . . . . . . 4 3.2. Elements of procedure . . . . . . . . . . . . . . . . . . 4
3.2.1. Interpretation of Node Administrative Tags . . . . . 4
3.2.2. Use of Node Administrative Tags . . . . . . . . . . . 5
3.2.3. Processing Node Administrative Tag changes . . . . . 6
4. Applications . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Applications . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Service auto-discovery . . . . . . . . . . . . . . . . . 6 4.1. Service auto-discovery . . . . . . . . . . . . . . . . . 6
4.2. Fast-Re-routing policy . . . . . . . . . . . . . . . . . 6 4.2. Fast-Re-routing policy . . . . . . . . . . . . . . . . . 7
4.3. Controlling Remote LFA tunnel termination . . . . . . . . 7 4.3. Controlling Remote LFA tunnel termination . . . . . . . . 8
4.4. Mobile back-haul network service deployment . . . . . . . 8 4.4. Mobile back-haul network service deployment . . . . . . . 8
4.5. Explicit routing policy . . . . . . . . . . . . . . . . . 9 4.5. Explicit routing policy . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. Operational Considerations . . . . . . . . . . . . . . . . . 11 6. Operational Considerations . . . . . . . . . . . . . . . . . 11
7. Manageability Considerations . . . . . . . . . . . . . . . . 11 7. Manageability Considerations . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1. Normative References . . . . . . . . . . . . . . . . . . 12 11.1. Normative References . . . . . . . . . . . . . . . . . . 12
11.2. Informative References . . . . . . . . . . . . . . . . . 13 11.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
It is useful to assign a per-node administrative tag to a router in It is useful to assign a per-node administrative tag to a router in
the OSPF domain and use it as an attribute associated with the node. the OSPF domain and use it as an attribute associated with the node.
The per-node administrative tag can be used in variety of The per-node administrative tag can be used in variety of
applications, for ex: - Traffic-engineering applications to provide applications, for example:
different path-selection criteria, - Prefer or prune certain paths in
Loop Free Alternate (LFA) backup selection via local policies. (a) Traffic-engineering applications to provide different path-
selection criteria.
(b) Prefer or prune certain paths in Loop Free Alternate (LFA)
backup selection via local policies as defined in
[I-D.ietf-rtgwg-lfa-manageability].
This document provides mechanisms to advertise per-node This document provides mechanisms to advertise per-node
administrative tags in OSPF for route and path selection. Route and administrative tags in OSPF for route and path selection. Route and
path selection functionality applies to both to TE and non-TE path selection functionality applies to both to TE and non Traffic
applications and hence new TLV for carrying per-node administrative Engineering (TE) applications and hence new TLV for carrying per-node
tags is included in Router Information LSA [RFC4970] . administrative tags is included in Router Information (RI) Link State
Advertisement (LSA) [I-D.ietf-ospf-rfc4970bis].
2. Administrative Tag TLV 2. Administrative Tag TLV
An administrative Tag is a 32-bit integer value that can be used to An administrative Tag is a 32-bit integer value that can be used to
identify a group of nodes in the OSPF domain. identify a group of nodes in the OSPF domain.
The new TLV defined will be carried within an RI LSA for OSPFV2 and The new TLV defined will be carried within an RI LSA for OSPFV2 and
OSPFV3. Router information LSA [RFC4970] can have link, area or AS OSPFV3. Router information (RI)LSA [I-D.ietf-ospf-rfc4970bis] can
level flooding scope. Choosing the flooding scope to flood the group have link-, area- or Autonomous Sytem (AS) level flooding scope. The
tags are defined by the policies and is a local matter. choice of what scope at which to flood the group tags is a matter of
local policy.It is expected that node administrative tag values will
not be portable across administrative domains.
The TLV specifies one or more administrative tag values. An OSPF The TLV specifies one or more administrative tag values. An OSPF
node advertises the set of groups it is part of in the OSPF domain. node advertises the set of groups it is part of in the OSPF domain
(for example, all PE-nodes are configured with certain tag value, all (for example, all PE-nodes are configured with certain tag value, all
P-nodes are configured with a different tag value in the domain). P-nodes are configured with a different tag value in the domain).
Multiple TLVs MAY be added in same RI-LSA or in a different instance Multiple TLVs MAY be added in same RI-LSA or in a different instance
of the RI LSA as defined in [I-D.acee-ospf-rfc4970bis]. of the RI LSA as defined in [I-D.ietf-ospf-rfc4970bis].
3. OSPF per-node administrative tag TLV 3. OSPF per-node administrative tag TLV
3.1. TLV format 3.1. TLV format
[RFC4970], defines Router Information (RI) LSA which may be used to [I-D.ietf-ospf-rfc4970bis], defines Router Information (RI) LSA which
advertise properties of the originating router. Payload of the RI may be used to advertise properties of the originating router. The
LSA consists of one or more nested Type/Length/Value (TLV) triplets. payload of the RI LSA consists of one or more nested Type/Length/
Node administrative tags are advertised in the Node Administrative Value (TLV) triplets. Node administrative tags are advertised in the
Tag TLV. The format of Node Administrative Tag TLV is: Node Administrative Tag TLV. The format of the Node Administrative
Tag TLV is:
0 1 2 3 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Administrative Tag #1 | | Administrative Tag #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Administrative Tag #2 | | Administrative Tag #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// // // //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Administrative Tag #N | | Administrative Tag #N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: OSPF per-node Administrative Tag TLV Figure 1: OSPF per-node Administrative Tag TLV
Type : TBA, Suggested value 10 Type : TBA, Suggested value 10
Length: A 16-bit field that indicates the length of the value portion Length: A 16-bit field that indicates the length of the value portion
in octets and will be a multiple of 4 octets dependent on the number in octets and will be a multiple of 4 octets dependent on the number
of tags advertised. of tags advertised.
Value: A sequence of multiple 4 octets defining the administrative Value: A sequence of multiple four octets defining the administrative
tags. At least one tag MUST be carried if this TLV is included in tags. At least one tag MUST be carried if this TLV is included in
the RI-LSA. the RI-LSA.
3.2. Elements of procedure 3.2. Elements of procedure
Meaning of the Node administrative tags is generally opaque to OSPF. 3.2.1. Interpretation of Node Administrative Tags
Router advertising the per-node administrative tag (or tags) may be
configured to do so without knowing (or even explicitly supporting) The meaning of the Node administrative tags is generally opaque to
functionality implied by the tag. OSPF. Routers advertising the per-node administrative tag (or tags)
may be configured to do so without knowing (or even without
supporting processing of) the functionality implied by the tag. This
section describes general rules/ regulations and guidelines for using
and interpreting an administrative tag which will facilitate
interoperable implementations by vendors.
Interpretation of tag values is specific to the administrative domain Interpretation of tag values is specific to the administrative domain
of a particular network operator, and hence tag values SHOULD NOT be of a particular network operator, and hence tag values SHOULD NOT be
propagated outside the administrative domain to which they apply. propagated outside the administrative domain to which they apply.
The meaning of a per-node administrative tag is defined by the The meaning of a per-node administrative tag is defined by the
network local policy and is controlled via the configuration. If a network local policy and is controlled via the configuration. If a
receiving node does not understand the tag value or does not have a receiving node does not understand the tag value or does not have a
local policy corresponding to the tag, it ignores the specific tag local policy corresponding to the tag, it ignores the specific tag
and floods the RI LSA without any change as defined in [RFC4970]. and floods the RI LSA without any change as defined in
[I-D.ietf-ospf-rfc4970bis].
The semantics of the tag order has no meaning. That is, there is no The semantics of the tag order has no meaning. That is, there is no
implied meaning to the ordering of the tags that indicates a certain implied meaning to the ordering of the tags that indicates a certain
operation or set of operations that need to be performed based on the operation or set of operations that need to be performed based on the
ordering. ordering.
Each tag MUST be treated as an independent identifier that MAY be Each tag must be treated as an independent identifier that may be
used in policy to perform a policy action. Tags carried by the used in policy to perform a policy action. Each tag carried by the
administrative tag TLV SHOULD be used to indicate independent administrative tag TLV should be used to indicate a characteristic of
characteristics of a node. The administrative tag list within the a node that is independent of the characteristics indicated by other
TLV MUST be considered an unordered list. Whilst policies may be administrative tags. The administrative tag list within the TLV MUST
implemented based on the presence of multiple tags (e.g., if tag A be considered an unordered list. Whilst policies may be implemented
AND tag B are present), they MUST NOT be reliant upon the order of based on the presence of multiple tags (e.g., if tag A AND tag B are
the tags (i.e., all policies should be considered commutative present), they MUST NOT be reliant upon the order of the tags (i.e.,
operations, such that tag A preceding or following tag B does not all policies should be considered commutative operations, such that
change their outcome). tag A preceding or following tag B does not change their outcome).
To avoid incomplete or inconsistent interpretations of the per-node To avoid incomplete or inconsistent interpretations of the per-node
administrative tags the same tag value MUST NOT be advertised by a administrative tags the same tag value MUST NOT be advertised by a
router in RI LSAs of different scopes. The same tag MAY be router in RI LSAs of different scopes. The same tag MAY be
advertised in multiple RI LSAs of the same scope, for example, OSPF advertised in multiple RI LSAs of the same scope, for example, OSPF
Area Border Router (ABR) may advertise the same tag in area-scope RI Area Border Router (ABR) may advertise the same tag in area-scope RI
LSAs in multiple areas connected to the ABR. LSAs in multiple areas connected to the ABR. If a node
administrative tag is received in different scopes, the conflicting
tag SHOULD not be used and this situation SHOULD be logged as an
error including the tag with conflicting scopes and the
originator(s). An ABR in a stub or NSSA area MAY originate AS scoped
RI LSAs and flood them into non-stub/NSSA areas and MAY originate
area scoped RI LSAs into the stub/NSSA areas as the AS scoped LSAs
are not flooded into stub/NSSA areas.
The per-node administrative tags are not meant to be extended by the 3.2.2. Use of Node Administrative Tags
future OSPF standards. The new OSPF extensions MUST NOT require use
of per-node administrative tags or define well-known tag values. The per-node administrative tags are not meant to be extended by
Node administrative tags are for generic use and do not require IANA future OSPF standards. New OSPF extensions are not expected to
registry. The future OSPF extensions requiring well known values MAY require use of per-node administrative tags or define well-known tag
define their own data signalling tailored to the needs of the feature values. Node administrative tags are for generic use and do not
or MAY use capability TLV as defined in [RFC4970]. require IANA registry. Future OSPF extensions requiring well known
values MAY define their own data signalling tailored to the needs of
the feature or MAY use the capability TLV as defined in
[I-D.ietf-ospf-rfc4970bis].
Being part of the RI LSA, the per-node administrative tag TLV must be Being part of the RI LSA, the per-node administrative tag TLV must be
reasonably small and stable. In particular, but not limited to, reasonably small and stable. In particular, implementations
implementations supporting the per-node administrative tags MUST NOT supporting per-node administrative tags MUST NOT be used to convey
tie advertised tags to changes in the network topology (both within attributes of the routing topology or associate tags with changes in
and outside the OSPF domain) or reachability of routes. the network topology (both within and outside the OSPF domain) or
reachability of routes.
3.2.3. Processing Node Administrative Tag changes
Multiple node administrative tag TLVs MAY appear in an RI LSA or Multiple node administrative tag TLVs MAY appear in an RI LSA or
multiple node administrative tag TLVs MAY be contained in different multiple node administrative tag TLVs MAY be contained in different
instances of the RI LSA. The node administrative tags associated instances of the RI LSA. The node administrative tags associated
with a node that originates tags for the purpose of any computation with a node that originates tags for the purpose of any computation
or processing at a receiving node SHOULD be a superset of node or processing at a receiving node SHOULD be a superset of node
administrative tags from all the TLVs in all the received RI LSA administrative tags from all the TLVs in all the received RI LSA
instances originated by that node.When an RI LSA is received that instances in the Link-State Database (LSDB) advertised by the
changes the set of tags applicable to any originating node, a corresponding OSPF router. When an RI LSA is received that changes
receiving node MUST repeat any computation or processing that is the set of tags applicable to any originating node, which has
based on those administrative tags. features depending on node administrative tags , a receiving node
MUST repeat any computation or processing that is based on those
administrative tags.
When there is a change or removal of an administrative affiliation of When there is a change or removal of an administrative affiliation of
a node, the node MUST re-originate the RI LSA with the latest set of a node, the node MUST re-originate the RI LSA with the latest set of
node administrative tags. On the receiver, When there is a change in node administrative tags. On the receiver, When there is a change in
the node administrative tag TLV or removal/ addition of a TLV in any the node administrative tag TLV or removal/ addition of a TLV in any
instance of the RI-LSA, implementations MUST take appropriate instance of the RI-LSA, implementations MUST take appropriate
measures to update its state according to the changed set of tags. measures to update their state according to the changed set of tags.
Exact actions depend on features working with administrative tags and The exact actions needed depend on features working with
is outside of scope of this specification. administrative tags and is outside of scope of this specification.
4. Applications 4. Applications
This section lists several examples of how implementations might use This section lists several examples of how implementations might use
the Node administrative tags. These examples are given only to the per-node administrative tags. These examples are given only to
demonstrate generic usefulness of the router tagging mechanism. demonstrate the generic usefulness of the router tagging mechanism.
Implementation supporting this specification is not required to Implementations supporting this specification are not required to
implement any of the use cases. It is also worth noting that in some implement any of these use cases. It is also worth noting that in
described use cases routers configured to advertise tags help other some described use cases routers configured to advertise tags help
routers in their calculations but do not themselves implement the other routers in their calculations but do not themselves implement
same functionality. the same functionality.
4.1. Service auto-discovery 4.1. Service auto-discovery
Router tagging may be used to automatically discover group of routers Router tagging may be used to automatically discover a group of
sharing a particular service. routers sharing a particular service.
For example, service provider might desire to establish full mesh of For example, a service provider might desire to establish a full mesh
MPLS TE tunnels between all PE routers in the area of MPLS VPN of MPLS TE tunnels between all PE routers in the area of the MPLS VPN
network. Marking all PE routers with a tag and configuring devices network. Marking all PE routers with a tag and configuring devices
with a policy to create MPLS TE tunnels to all other devices with a policy to create MPLS TE tunnels to all other devices
advertising this tag will automate maintenance of the full mesh. advertising this tag will automate maintenance of the full mesh.
When new PE router is added to the area, all other PE devices will When new PE router is added to the area, all other PE devices will
open TE tunnels to it without the need of reconfiguring them. open TE tunnels to it without the need of reconfiguring them.
4.2. Fast-Re-routing policy 4.2. Fast-Re-routing policy
Increased deployment of Loop Free Alternates (LFA) as defined in Increased deployment of Loop Free Alternates (LFA) as defined in
[RFC5286] poses operation and management challenges. [RFC5286] poses operation and management challenges.
[I-D.ietf-rtgwg-lfa-manageability] proposes policies which, when [I-D.ietf-rtgwg-lfa-manageability] proposes policies which, when
implemented, will ease LFA operation concerns. implemented, will ease LFA operation concerns.
One of the proposed refinements is to be able to group the nodes in One of the proposed refinements is to be able to group the nodes in
IGP domain with administrative tags and engineer the LFA based on an IGP domain with administrative tags and engineer the LFA based on
configured policies. configured policies.
(a) Administrative limitation of LFA scope (a) Administrative limitation of LFA scope
Service provider access infrastructure is frequently designed in Service provider access infrastructure is frequently designed in
layered approach with each layer of devices serving different a layered approach with each layer of devices serving different
purposes and thus having different hardware capabilities and purposes and thus having different hardware capabilities and
configured software features. When LFA repair paths are being configured software features. When LFA repair paths are being
computed, it may be desirable to exclude devices from being computed, it may be desirable to exclude devices from being
considered as LFA candidates based on their layer. considered as LFA candidates based on their layer.
For example, if the access infrastructure is divided into the For example, if the access infrastructure is divided into the
Access, Distribution and Core layers it may be desirable for a Access, Distribution and Core layers it may be desirable for a
Distribution device to compute LFA only via Distribution or Core Distribution device to compute LFA only via Distribution or Core
devices but not via Access devices. This may be due to features devices but not via Access devices. This may be due to features
enabled on Access routers; due to capacity limitations or due to enabled on Access routers, due to capacity limitations or due to
the security requirements. Managing such a policy via the security requirements. Managing such a policy via
configuration of the router computing LFA is cumbersome and error configuration of the router computing LFA is cumbersome and error
prone. prone.
With the Node administrative tags it is possible to assign a tag With the Node administrative tags it is possible to assign a tag
to each layer and implement LFA policy of computing LFA repair to each layer and implement LFA policy of computing LFA repair
paths only via neighbors which advertise the Core or Distribution paths only via neighbors which advertise the Core or Distribution
tag. This requires minimal per-node configuration and network tag. This requires minimal per-node configuration and the
automatically adapts when new links or routers are added. network automatically adapts when new links or routers are added.
(b) LFA calculation optimization (b) LFA calculation optimization
Calculation of LFA paths may require significant resources of the Calculation of LFA paths may require significant resources of the
router. One execution of Dijkstra algorithm is required for each router. One execution of Dijkstra's algorithm is required for
neighbor eligible to become next hop of repair paths. Thus a each neighbor eligible to become the next hop of repair paths.
router with a few hundreds of neighbors may need to execute the
algorithm hundreds of times before the best (or even valid) Thus, a router with a few hundreds of neighbors may need to
repair path is found. Manually excluding from the calculation execute the algorithm hundreds of times before the best (or even
neighbors which are known to provide no valid LFA (such as valid) repair path is found. Manually excluding from the
single-connected routers) may significantly reduce number of calculation neighbors that are known to provide no valid LFA
Dijkstra algorithm runs. (such as single-connected routers) may significantly reduce
number of Dijkstra algorithm runs.
LFA calculation policy may be configured so that routers LFA calculation policy may be configured so that routers
advertising certain tag value are excluded from LFA calculation advertising certain tag value are excluded from LFA calculation
even if they are otherwise suitable. even if they are otherwise suitable.
4.3. Controlling Remote LFA tunnel termination 4.3. Controlling Remote LFA tunnel termination
[RFC7490] defined a method of tunnelling traffic after connected link [RFC7490] defined a method of tunnelling traffic after connected link
failure to extend the basic LFA coverage and algorithm to find tunnel failure to extend the basic LFA coverage and an algorithm to find
tail-end routers fitting LFA requirement. In most cases proposed tunnel tail-end routers fitting LFA requirement. In most cases the
algorithm finds more than one candidate tail-end router. In real proposed algorithm finds more than one candidate tail-end router. In
life network it may be desirable to exclude some nodes from the list real-life network it may be desirable to exclude some nodes from the
of candidates based on the local policy. This may be either due to list of candidates based on the local policy. This may be either due
known limitations of the node (the router does not accept targeted to known limitations of the node (the router does not accept the
LDP sessions required to implement Remote LFA tunnelling) or due to targeted LDP sessions required to implement Remote LFA tunnelling) or
administrative requirements (for example, it may be desirable to due to administrative requirements (for example, it may be desirable
choose tail-end router among co-located devices). to choose the tail-end router among co-located devices).
The Node administrative tag delivers simple and scalable solution. The Node administrative tag delivers a simple and scalable solution.
Remote LFA can be configured with a policy to accept during the tail- Remote LFA can be configured with a policy to accept during the tail-
end router calculation as candidates only routers advertising certain end router calculation as candidates only routers advertising a
tag. Tagging routers allows to both exclude nodes not capable of certain tag. Tagging routers allows to both exclude nodes not
serving as Remote LFA tunnel tail-ends and to define a region from capable of serving as Remote LFA tunnel tail-ends and to define a
which tail-end router must be selected. region from which tail-end router must be selected.
4.4. Mobile back-haul network service deployment 4.4. Mobile back-haul network service deployment
The topology of mobile back-haul network usually adopts ring topology Mobile back-haul networks usually adopt a ring topology to save fibre
to save fibre resource and it is divided into the aggregate network resources; it is usually divided into the aggregate network and the
and the access network. Cell Site Gateways(CSGs) connects the access network. Cell Site Gateways(CSGs) connects the eNodeBs and
eNodeBs and RNC(Radio Network Controller) Site Gateways(RSGs) RNC(Radio Network Controller) Site Gateways(RSGs) connects the RNCs.
connects the RNCs. The mobile traffic is transported from CSGs to The mobile traffic is transported from CSGs to RSGs. The network
RSGs. The network takes a typical aggregate traffic model that more takes a typical aggregate traffic model that more than one access
than one access rings will attach to one pair of aggregate site rings will attach to one pair of aggregate site gateways(ASGs) and
gateways(ASGs) and more than one aggregate rings will attach to one more than one aggregate rings will attach to one pair of RSGs.
pair of RSGs.
---------------- ----------------
/ \ / \
/ \ / \
/ \ / \
+------+ +----+ Access +----+ +------+ +----+ Access +----+
|eNodeB|---|CSG1| Ring 1 |ASG1|------------ |eNodeB|---|CSG1| Ring 1 |ASG1|------------
+------+ +----+ +----+ \ +------+ +----+ +----+ \
\ / \ \ / \
\ / +----+ +---+ \ / +----+ +---+
skipping to change at page 8, line 47 skipping to change at page 9, line 33
+------+ +----+ +----+ +------+ +----+ +----+
\ / \ /
\ / \ /
\ / \ /
----------------- -----------------
Figure 2: Mobile Backhaul Network Figure 2: Mobile Backhaul Network
A typical mobile back-haul network with access rings and aggregate A typical mobile back-haul network with access rings and aggregate
links is shown in figure above. The mobile back-haul networks deploy links is shown in figure above. The mobile back-haul networks deploy
traffic engineering due to the strict Service Level Agreements(SLA). traffic engineering due to strict Service Level Agreements(SLA). The
The TE paths may have additional constraints to avoid passing via Traffic Engineering(TE) paths may have additional constraints to
different access rings or to get completely disjoint backup TE paths. avoid passing via different access rings or to get completely
The mobile back-haul networks towards the access side change disjoint backup TE paths. The mobile back-haul networks towards the
frequently due to the growing mobile traffic and addition of new LTE access side change frequently due to the growing mobile traffic and
Evolved NodeBs (eNodeB). It's complex to satisfy the requirements addition of new LTE Evolved NodeBs (eNodeB). It's complex to satisfy
using cost, link color or explicit path configurations. The node the requirements using cost, link color or explicit path
administrative tag defined in this document can be effectively used configurations. The node administrative tag defined in this document
to solve the problem for mobile back-haul networks. The nodes in can be effectively used to solve the problem for mobile back-haul
different rings can be assigned with specific tags. TE path networks. The nodes in different rings can be assigned with specific
computation can be enhanced to consider additional constraints based tags. TE path computation can be enhanced to consider additional
on node administrative tags. constraints based on node administrative tags.
4.5. Explicit routing policy 4.5. Explicit routing policy
Partially meshed network provides multiple paths between any two A partially meshed network provides multiple paths between any two
nodes in the network. In a data centre environment, the topology is nodes in the network. In a data centre environment, the topology is
usually highly symmetric with many/all paths having equal cost. In a usually highly symmetric with many/all paths having equal cost. In a
long distance network, this is usually less the case for a variety of long distance network, this is usually less the case, for a variety
reasons (e.g. historic, fibre availability constraints, different of reasons (e.g. historic, fibre availability constraints, different
distances between transit nodes, different roles ...). Hence between distances between transit nodes, different roles ...). Hence between
a given source and destination, a path is typically preferred over a given source and destination, a path is typically preferred over
the others, while between the same source and another destination, a the others, while between the same source and another destination, a
different path may be preferred. different path may be preferred.
+--------------------+ +----------------------+ +----------------+
| | | \ / |
| +----------+ | | +-----------------+ x +---------+ |
| | | | | | \/ \/ | |
+-T-10-T | | | | +-T-10-T | |
/ | /| | | | | / | /| | |
/ 100 / | | | | | / 100 / | | |
/ | | 100 | | | | / | | 100 | |
/ +-+-+ | | | | | / +-+-+ | | |
/ / | | | | | | / / | | | |
/ / R-18-R | | | | / / R-18-R | |
10 10 /\ /\ | | | | 10 10 /\ /\ | |
/ / / \ / \ | | | | / / / \ / \ | |
/ | / x \ | | | | / / / x \ | |
A-25-A 10 10 \ \ | | | | / / 10 10 \ \ | |
/ / 10 10 | | | | / / / / 10 10 | |
/ / \ \ | | | | / / / / \ \ | |
A-25-A A-25-A | | | | A-25-A A-25-A A-25-A | |
\ \ / / | | | | | | \ \ / / | |
201 201 201 201 | | | | | | 201 201 201 201 | |
\ \ / / | | | | | | \ \ / / | |
\ x / | | | | 201 201 \ x / | |
\ / \ / | | | | | | \ / \ / | |
\/ \/ | | | | | | \/ \/ | |
I-24-I 100 100 | | I-24-I I-24-I 100 100
| | | | | | / / | | | |
| +-----------+ | | +-+ / | +-----------+ |
| | +---------+ +---------------------+
+---------------------+
Figure 3: Explicit Routing topology Figure 3: Explicit Routing topology
In the above topology, operator may want to enforce the following In the above topology, operator may want to enforce the following
high level explicit routing policies: high level explicit routing policies:
- Traffic from A nodes to A nodes should preferably go through R - Traffic from A nodes to A nodes should preferably go through R
or T nodes (rather than through I nodes); or T nodes (rather than through I nodes);
- Traffic from A nodes to I nodes must not go through R and T - Traffic from A nodes to I nodes must not go through R and T
skipping to change at page 11, line 14 skipping to change at page 11, line 22
having the tag "A" runs a CSPF with the exclusion of nodes having the having the tag "A" runs a CSPF with the exclusion of nodes having the
tag "I". tag "I".
5. Security Considerations 5. Security Considerations
Node administrative tags may be used by operators to indicate Node administrative tags may be used by operators to indicate
geographical location or other sensitive information. As indicated geographical location or other sensitive information. As indicated
in [RFC2328] and [RFC5340] OSPF authentication mechanisms do not in [RFC2328] and [RFC5340] OSPF authentication mechanisms do not
provide confidentiality and the information carried in node provide confidentiality and the information carried in node
administrative tags could be leaked to an IGP snooper. administrative tags could be leaked to an IGP snooper.
Confidentiality for the OSPF control packets can be achieved by
either running OSPF on top of IP Security (IPSEC) tunnels or by
applying IPSEC based security mechanisms as described in [RFC4552].
Advertisement of tag values for one administrative domain into Advertisement of tag values for one administrative domain into
another risks misinterpretation of the tag values (if the two domains another risks misinterpretation of the tag values (if the two domains
have assigned different meanings to the same values), which may have have assigned different meanings to the same values), which may have
undesirable and unanticipated side effects. undesirable and unanticipated side effects.
[RFC4593] and [RFC6863] discuss the generic threats to routing
protocols and OSPF respectively. These security threats are also
applicable to the mechanisms described in this document.OSPF
authentication described in [RFC2328] and [RFC5340] or extended
authentication mechanisms described in [RFC7474] or [RFC7166] SHOULD
be used in deployments where attackers have access to the physical
networks and nodes included in the OSPF domain are vulnerable.
6. Operational Considerations 6. Operational Considerations
Operators can assign meaning to the node administrative tags which is Operators can assign meaning to the node administrative tags which is
local to the operator's administrative domain. The operational use local to the operator's administrative domain. The operational use
of node administrative tags is analogical to the IS-IS prefix tags of node administrative tags is analogical to the IS-IS prefix tags
[RFC5130] and BGP communities [RFC1997]. Operational discipline and [RFC5130] and BGP communities [RFC1997]. Operational discipline and
procedures followed in configuring and using BGP communities and ISIS procedures followed in configuring and using BGP communities and ISIS
Prefix tags is also applicable to the usage of node administrative Prefix tags is also applicable to the usage of node administrative
tags. tags.
skipping to change at page 12, line 28 skipping to change at page 12, line 46
inputs. Thanks to Chris Bowers for providing useful inputs to remove inputs. Thanks to Chris Bowers for providing useful inputs to remove
ambiguity related to tag-ordering. Thanks to Les Ginsberg and Acee ambiguity related to tag-ordering. Thanks to Les Ginsberg and Acee
Lindem for the inputs. Thanks to David Black for careful review and Lindem for the inputs. Thanks to David Black for careful review and
valuable suggestions for the document especially for the operations valuable suggestions for the document especially for the operations
section. section.
11. References 11. References
11.1. Normative References 11.1. Normative References
[I-D.acee-ospf-rfc4970bis] [I-D.ietf-ospf-rfc4970bis]
Lindem, A., Shen, N., Vasseur, J., Aggarwal, R., and S. Lindem, A., Shen, N., Vasseur, J., Aggarwal, R., and S.
Shaffer, "Extensions to OSPF for Advertising Optional Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", draft-acee-ospf-rfc4970bis-00 (work Router Capabilities", draft-ietf-ospf-rfc4970bis-07 (work
in progress), July 2014. in progress), October 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998, DOI 10.17487/RFC2328, April 1998,
<http://www.rfc-editor.org/info/rfc2328>. <http://www.rfc-editor.org/info/rfc2328>.
skipping to change at page 13, line 33 skipping to change at page 14, line 5
[I-D.ietf-rtgwg-policy-model] [I-D.ietf-rtgwg-policy-model]
Shaikh, A., rjs@rob.sh, r., D'Souza, K., and C. Chase, Shaikh, A., rjs@rob.sh, r., D'Souza, K., and C. Chase,
"Routing Policy Configuration Model for Service Provider "Routing Policy Configuration Model for Service Provider
Networks", draft-ietf-rtgwg-policy-model-00 (work in Networks", draft-ietf-rtgwg-policy-model-00 (work in
progress), September 2015. progress), September 2015.
[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities [RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities
Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996, Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
<http://www.rfc-editor.org/info/rfc1997>. <http://www.rfc-editor.org/info/rfc1997>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<http://www.rfc-editor.org/info/rfc4552>.
[RFC4593] Barbir, A., Murphy, S., and Y. Yang, "Generic Threats to
Routing Protocols", RFC 4593, DOI 10.17487/RFC4593,
October 2006, <http://www.rfc-editor.org/info/rfc4593>.
[RFC5130] Previdi, S., Shand, M., Ed., and C. Martin, "A Policy [RFC5130] Previdi, S., Shand, M., Ed., and C. Martin, "A Policy
Control Mechanism in IS-IS Using Administrative Tags", Control Mechanism in IS-IS Using Administrative Tags",
RFC 5130, DOI 10.17487/RFC5130, February 2008, RFC 5130, DOI 10.17487/RFC5130, February 2008,
<http://www.rfc-editor.org/info/rfc5130>. <http://www.rfc-editor.org/info/rfc5130>.
[RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for
IP Fast Reroute: Loop-Free Alternates", RFC 5286, IP Fast Reroute: Loop-Free Alternates", RFC 5286,
DOI 10.17487/RFC5286, September 2008, DOI 10.17487/RFC5286, September 2008,
<http://www.rfc-editor.org/info/rfc5286>. <http://www.rfc-editor.org/info/rfc5286>.
[RFC6863] Hartman, S. and D. Zhang, "Analysis of OSPF Security
According to the Keying and Authentication for Routing
Protocols (KARP) Design Guide", RFC 6863,
DOI 10.17487/RFC6863, March 2013,
<http://www.rfc-editor.org/info/rfc6863>.
[RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting
Authentication Trailer for OSPFv3", RFC 7166,
DOI 10.17487/RFC7166, March 2014,
<http://www.rfc-editor.org/info/rfc7166>.
[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<http://www.rfc-editor.org/info/rfc7474>.
Authors' Addresses Authors' Addresses
Shraddha Hegde Shraddha Hegde
Juniper Networks, Inc. Juniper Networks, Inc.
Embassy Business Park Embassy Business Park
Bangalore, KA 560093 Bangalore, KA 560093
India India
Email: shraddha@juniper.net Email: shraddha@juniper.net
Rob Shakir Rob Shakir
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