One document matched: draft-hegde-ospf-node-admin-tag-02.xml
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<rfc category="std" docName="draft-hegde-ospf-node-admin-tag-02" ipr="trust200902">
<front>
<title abbrev="OSPF router admin tags">Advertising per-node administrative tags in OSPF</title>
<author initials="S." surname="Hegde" fullname="Shraddha Hegde">
<organization>Juniper Networks, Inc.</organization>
<address>
<postal>
<street>Embassy Business Park</street>
<city>Bangalore</city>
<region>KA</region>
<code>560093</code>
<country>India</country>
</postal>
<email>shraddha@juniper.net</email>
</address>
</author>
<author initials="H." surname="Raghuveer" fullname="Harish Raghuveer">
<organization>Juniper Networks, Inc.</organization>
<address>
<postal>
<street>Embassy Business Park</street>
<city>Bangalore</city>
<code>560093</code>
<country>India</country>
</postal>
<email>hraghuveer@juniper.net</email>
</address>
</author>
<author fullname="Hannes Gredler" initials="H." surname="Gredler">
<organization>Juniper Networks, Inc.</organization>
<address>
<postal>
<street>1194 N. Mathilda Ave.</street>
<city>Sunnyvale</city>
<region>CA</region>
<code>94089</code>
<country>US</country>
</postal>
<email>hannes@juniper.net</email>
</address>
</author>
<author fullname="Rob Shakir" initials="R." surname="Shakir">
<organization>British Telecom</organization>
<address>
<postal>
<street> </street>
<city> </city>
<region> </region>
<code> </code>
<country> </country>
</postal>
<email>rob.shakir@bt.com</email>
</address>
</author>
<author fullname="Anton Smirnov" initials="A." surname="Smirnov">
<organization>Cisco Systems, Inc.</organization>
<address>
<postal>
<street>De Kleetlaan 6a</street>
<city>Diegem</city>
<region/>
<code>1831</code>
<country>Belgium</country>
</postal>
<email>as@cisco.com</email>
</address>
</author>
<author fullname="Li Zhenbin" initials="Z." surname="Li">
<organization>Huawei Technologies</organization>
<address>
<postal>
<street>Huawei Bld. No.156 Beiqing Rd</street>
<city> Beijing</city>
<region/>
<code>100095</code>
<country>China</country>
</postal>
<email>lizhenbin@huawei.com</email>
</address>
</author>
<date day="26" month="June" year="2014"/>
<area>Routing</area>
<workgroup>Open Shortest Path First IGP</workgroup>
<keyword>MPLS</keyword>
<keyword>IGP</keyword>
<keyword>OSPF</keyword>
<keyword>admin-tag</keyword>
<keyword>traffic engineering</keyword>
<abstract>
<t> This document describes an extension to OSPF protocol <xref target="RFC2328" /> to
add an optional operational capability, that allows tagging and grouping of
the nodes in an OSPF domain. This allows simplification,ease of management and
control over route and path selection based on configured policies. </t>
<t>This document describes the protocol extensions to disseminate
per-node admin-tags to the OSPFv2 and OSPFv3 protocol.</t>
</abstract>
<note title="Requirements Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction" anchor='intro'>
<t> This document provides mechanisms to advertise per-node administrative
tags in the OSPF Router Information LSA <xref target="RFC4970"/>.
In certain path-selection applications like for example in traffic-engineering
or LFA backup selection there is a need to tag the nodes
based on their roles in the network and have policies to prefer or
prune a certain group of nodes.
</t>
</section>
<section title='Applicability'>
<t> For the purpose of advertising per-node administrative tags within OSPF
a new TLV is proposed. Because path selection is a functional set which applies
both to TE and non-TE applications, this new TLV is carried in
the Router Information LSA (RI LSA) <xref target="RFC4970"/>
</t>
</section>
<section title='Administrative Tag TLV'>
<t> An administrative Tag is a 32-bit integer value that can be
used to identify a group of nodes in the OSPF domain.
<vspace blankLines="1" />
The new TLV defined will be carried within an RI LSA for OSPFV2 and
OSPFV3. Router information LSA <xref target="RFC4970"/> can have link,area or AS level
flooding scope. Choosing the flooding scope to flood the group
tags are defined by the policies and is a local matter.
<vspace blankLines="1" />
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.
(for example, all PE-nodes are configured with certain tag value,
all P-nodes are configured with a different tag value in a domain).
The total number of admin tags that a given router can advertise at one time
is restricted to 64. If more tags are needed in future, multi-instancing of the
RI LSA <xref target="RFC4970"/> may be required.
</t>
</section>
<section title='OSPF per-node administrative tag TLV'>
<section title='TLV format'>
<t>The format of the TLVs within the body of an RI LSA is the same
as the format used by the Traffic Engineering Extensions to OSPF
<xref target="RFC3630"/>.
<vspace blankLines="1" />
The LSA payload consists of one or more nested Type/Length/Value
(TLV) triplets. The format of each TLV is:
<vspace blankLines="2" />
<figure anchor="OSPF-Admin-tag-TLV" title="OSPF per-node Administrative Tag TLV">
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Administrative Tag #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Administrative Tag #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Administrative Tag #N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure>
<vspace blankLines="1" />
<vspace blankLines="1" />
Type : TBA
<vspace blankLines="1" />
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 of tags advertised.
<vspace blankLines="1" />
Value: A sequence of multiple 4 octets defining the
administrative tags. The number of tags carried in this
TLV is restricted to 64.
</t>
</section>
<section title='Elements of procedure'>
<t>Meaning of the Node administrative tags is generally
opaque to OSPF. Router advertising the Node
administrative tag (or tags) may be configured to do so
without knowing (or even explicitly supporting)
functionality implied by the tag.</t>
<t>Interpretation of the tag values is
implementation-specific. The meaning of a Node
administrative tag is defined by the network local policy
and is controlled via the configuration. There are no tag
values defined by this specification.</t>
<t>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 operation or set of operations
that need to be performed based on the ordering.</t>
<t>Each tag SHOULD be treated as an independent
identifier that MAY be used in policy to perform a policy
action. Whether or not tag A precedes or succeeds tag B
SHOULD not change the meaning of the tag set.</t>
<t>To avoid incomplete or inconsistent interpretations of
the Node administrative tags the same tag value MUST NOT
be advertised by a router in RI LSAs of different
scopes. The same tag MAY be 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
LSAs in multiple areas connected to the ABR.</t>
<t>The Node administrative tags are not meant to be
extended by the future OSPF standards. The new OSPF
extensions MUST NOT require use of Node administrative
tags or define well-known tag values. Instead, the future
OSPF extensions must define their own data signaling
tailored to the needs of the feature.</t>
<t>Being part of the RI LSA, the Node administrative tag
TLV must be reasonably small and stable. In particular,
but not limited to, implementations supporting the Node
administrative tags MUST NOT tie advertised tags to
changes in the network topology (both within and outside
the OSPF domain) or reachability of routes.</t>
</section>
</section>
<section title='Applications'>
<t>This section lists several examples of how implementations
might use the Node administrative tags. These examples are
given only to demonstrate generic usefulness of the router
tagging mechanism. Implementation supporting this
specification is not required to implement any of the use
cases. It is also worth noting that in some described use
cases routers configured to advertise tags help other routers
in their calculations but do not themselves implement the
same functionality.
<list style="numbers">
<t>Service auto-discovery
<vspace blankLines="1"/>
Router tagging may be used to automatically discover
group of routers sharing a particular service.
<vspace blankLines="1"/>
For example, service provider might desire to establish
full mesh of MPLS TE tunnels between all PE routers in
the area of MPLS VPN network. Marking all PE routers with
a tag and configuring devices with a policy to create
MPLS TE tunnels to all other devices advertising this tag
will automate maintenance of the full mesh. 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.
</t>
<t>Fast-Rerouting policy
<vspace blankLines="1"/>
Increased deployment of Loop Free Alternates (LFA) as
defined in <xref target="RFC5286"/> poses operation and
management challenges. <xref
target="I-D.litkowski-rtgwg-lfa-manageability"/> proposes
policies which, when implemented, will ease LFA operation
concerns.
<vspace blankLines="1"/>
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 configured policies.
<list style="format (%c)" hangIndent="4">
<t>Administrative limitation of LFA scope
<vspace blankLines="1"/>
Service provider access infrastructure is frequently
designed in layered approach with each layer of
devices serving different purposes and thus having
different hardware capabilities and configured
software features. When LFA repair paths are being
computed, it may be desirable to exclude devices from
being considered as LFA candidates based on their
layer.
<vspace blankLines="1"/>
For example, if the access infrastructure is divided
into the Access, Distribution and Core layers it may
be desirable for a Distribution device to compute LFA
only via Distribution or Core devices but not via
Access devices. This may be due to features enabled
on Access routers; due to capacity limitations or due
to the security requirements. Managing such a policy
via configuration of the router computing LFA is
cumbersome and error prone.
<vspace blankLines="1"/>
With the Node administrative tags it is possible to
assign a tag to each layer and implement LFA policy
of computing LFA repair paths only via neighbors
which advertise the Core or Distribution tag. This
requires minimal per-node configuration and network
automatically adapts when new links or routers are
added.
</t>
<t>LFA calculation optimization
<vspace blankLines="1"/>
Calculation of LFA paths may require significant
resources of the router. One execution of Dijkstra
algorithm is required for each neighbor eligible to
become next hop of repair paths. Thus a router with a
few hundreds of neighbors may need to execute the
algorithm hundreds of times before the best (or even
valid) repair path is found. Manually excluding from
the calculation neighbors which are known to provide
no valid LFA (such as single-connected routers) may
significantly reduce number of Dijkstra algorithm
runs.
<vspace blankLines="1"/>
LFA calculation policy may be configured so that
routers advertising certain tag value are excluded
from LFA calculation even if they are otherwise
suitable.
</t>
</list>
</t>
<t>Controlling Remote LFA tunnel termination
<vspace blankLines="1"/>
<xref target="I-D.ietf-rtgwg-remote-lfa"/> proposed
method of tunneling traffic after connected link failure
to extend the basic LFA coverage and algorithm to find
tunnel tail-end routers fitting LFA requirement. In most
cases proposed algorithm finds more than one candidate
tail-end router. In real life network it may be desirable
to exclude some nodes from the list of candidates based
on the local policy. This may be either due to known
limitations of the node (the router does accept targeted
LDP sessions required to implement Remote LFA tunneling)
or due to administrative requirements (for example, it
may be desirable to choose tail-end router among
co-located devices).
<vspace blankLines="1"/>
The Node administrative tag delivers simple and scalable
solution. Remote LFA can be configured with a policy to
accept during the tail-end router calculation as
candidates only routers advertising certain tag. Tagging
routers allows to both exclude nodes not capable of
serving as Remote LFA tunnel tail-ends and to define a
region from which tail-end router must be selected.
</t>
<t>Mobile backhaul network service deployment
<vspace blankLines="1"/>
The topology of mobile backhaul network usually adopts ring topology
to save fiber resource and it is divided into the aggregate network and
the access network. Cell Site Gateways(CSGs) connects the eNodeBs and
RNC(Radio Network Controller) Site Gateways(RSGs)connects the RNCs.
The mobile traffic is transported from CSGs to RSGs. The network takes
a typical aggregate traffic model that more than one access rings will
attach to one pair of aggregate site gateways(ASGs) and more than one
aggregate rings will attach to one pair of RSGs.
<vspace blankLines="1"/>
<figure anchor="mobile-backhaul-network" title="Mobile Backhaul Network">
<artwork>
----------------
/ \
/ \
/ \
+------+ +----+ Access +----+
|eNodeB|---|CSG1| Ring 1 |ASG1|-------------
+------+ +----+ +----+ \
\ / \
\ / +----+ +---+
\ +----+ |RSG1|----|RNC|
-------------| | Aggregate +----+ +---+
|ASG2| Ring |
-------------| | +----+ +---+
/ +----+ |RSG2|----|RNC|
/ \ +----+ +---+
/ \ /
+------+ +----+ Access +----+ /
|eNodeB|---|CSG2| Ring 2 |ASG3|------------
+------+ +----+ +----+
\ /
\ /
\ /
-----------------
</artwork>
</figure>
<vspace blankLines="1"/>
A typical mobile backhaul network with access rings and aggregate
links is shown in figure above. The mobile backhaul networks deploy
traffic engineering due to the strict Service Level Agreements(SLA).
The TE paths may have additional constraints to avoid passing via different
access rings or to get completely disjoint backup TE paths. The mobile backhaul
networks towards the access side change frequently due to the growing mobile
traffic and addition of new eNodeBs. It's complex to satisfy the requirements
using cost, link color or explicit path configurations.
The node administrative tag defined in this document can be effectively used
to solve the problem for mobile backhaul networks. The nodes in different rings
can be assigned with specific tags. TE path computation can be enhanced to
consider additional constraints based on node administrative tags. </t>
</list>
</t>
</section>
<!-- HG: FIXME: add traffic-engineering reference -->
<section title='Security Considerations' anchor='sec-con'>
<t>
This document does not introduce any further security issues other
than those discussed in <xref target="RFC2328"/> and <xref target="RFC5340"/>.
</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>IANA maintains the registry for the TLVs. OSPF Administrative Tags
will require one new type code for the TLV defined in this document.
</t>
</section>
<section title='Acknowledgments'>
<t>Thanks to Bharath R and Pushpasis Sarakar for useful inputs. Thanks to Chris Bowers
for providing useful inputs to remove ambiguity related to tag-ordering.
</t>
</section>
</middle>
<back>
<references title='Normative References'>
&RFC2328;
&RFC5340;
&RFC3630;
&RFC4970;
&RFC2119;
</references>
<references title='Informative References'>
&RFC5286;
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-litkowski-rtgwg-lfa-manageability-01.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-rtgwg-remote-lfa-02.xml"?>
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 04:20:28 |