inter-domain routing with shared risk/resource groups (srg)jain/talks/ftp/srg02.pdfinter-domain...

InterInter--domain Routing withdomain Routing withShared Risk/Resource Groups (SRG)Shared Risk/Resource Groups (SRG)

Sudheer Dharanikota Sudheer Dharanikota -- [email protected]@ieee.orgNayna Networks, Inc.Nayna Networks, Inc.

MPLS World Congress 2002MPLS World Congress 2002February 8February 8thth 20022002

Raj Jain

jain@cse thin horizontal

February 8th 2002 2

CoCo--authorsauthors

Sudheer Dharanikota, Sudheer Dharanikota, Raj Jain Raj Jain –– Nayna NetworksNayna NetworksYong Yong XueXue, Curtis , Curtis Brownmiller Brownmiller –– WorldcomWorldcom

Dimitri Papadimitriou Dimitri Papadimitriou –– AlcatelAlcatelRiad Hartani Riad Hartani –– Caspian NetworksCaspian Networks

Greg Bernstein Greg Bernstein –– CienaCienaVishal Vishal Sharma Sharma –– MetanoiaMetanoia

John Strand John Strand –– AT&TAT&T

February 8th 2002 3

OutlineOutline

BackgroundBackgroundShared Risk Group (SRG)Shared Risk Group (SRG)SRG applicationsSRG applicationsSRG exampleSRG exampleConclusionsConclusionsReferencesReferencesQuestion and answersQuestion and answers

February 8th 2002 4

OutlineOutline

BackgroundBackgroundShared Risk Groups (SRG)Shared Risk Groups (SRG)SRG applicationsSRG applicationsSRG exampleSRG exampleConclusionsConclusionsReferencesReferencesQuestion and answersQuestion and answers

February 8th 2002 5

Background Background –– What is the problem?What is the problem?

Problem:Problem: Need a concept of a Need a concept of a domaindomain (control domain (control domain -- ITU) in ITU) in transport networks.transport networks.

Why?Why?To hide vendor clouds (unlike in router world)To make a transition from legacy equipmentTo have different cost centers in a carrier

So…So…We introduce the concept of a domainMake incremental changes to routing protocolsWe demonstrate its usage using P&R as a case study.

February 8th 2002 6

Background Background –– Node diversityNode diversity

A

B

C

D

F

E

G

Primary path

Secondary path

Node Failure

NODEDIVERSITY

February 8th 2002 7

Background Background –– Link and SRLG diversityLink and SRLG diversity

A

B

C

D

F

E

G

LinkFailure

Primary path

Secondary pathConduit

ConduitFailure

Link Diversity

SRLGDiversity

February 8th 2002 8

Earthquake zone

Background Background -- SRGSRG

Card

Node

Link (SRLG)

Trunk

Group of links sharing the same riskA link may be

member of many SRLGs

CO

Shared Risk Node Group Risks are not limited to linksNodes also share risksA single node failure can

bring down many linksUsers may want to avoid

nodal risks

A

B

C

L2

L3

Shared Risk Domain Group (SRDG)

Domain = A group of arbitrarily connected nodes and links possible with some common characteristics (Same administration, same technology, same risk)

A

C

B

L1

L2

L3

Boston

CentralOffice

February 8th 2002 9

Background Background –– SRG (Contd.)SRG (Contd.)

SRG = {SRLG, SRNG, SRDG, …}SRG = {SRLG, SRNG, SRDG, …}SRLG’s are a subset ofSRLG’s are a subset of SRG’s SRG’s Helps reduce computational complexityHelps reduce computational complexityUsers may want to have diverse paths not sharing Users may want to have diverse paths not sharing (Exclusive (Exclusive constraints)constraints) the same the same SRGs SRGs

A

SRG=1078

SRG=1132

B

February 8th 2002 10

Background Background -- MultiMulti--layer TElayer TE

Fiber topology

SRLG

Packet topology

SRG (Domain capabilities)

Observation: SRLG makes sense only at the interface of the lowest two layers.

SONET topology

SRG (Domain capabilities)

Optical topology

Note: Fiber layer is aServer layer to opticalLayer clients


Background Background –– MultiMulti--layer TElayer TE

A

C

BD

E

G

F

Client layer

Server layer

Logical server links


OutlineOutline



SRG SRG –– Domain capabilitiesDomain capabilities

Observation 1: Failure is restricted to a local scope (Observation 1: Failure is restricted to a local scope (Risk DomainRisk Domain) by ) by proper network planningproper network planning

For example risks such asCard failures are addressed by 1+1, 1:1 or M:N card redundancyNode failures are addressed by restartable code, redundancy or by node diversityCO failures are averted by redundant equipment (power supplies etc.)Link/Span failure is addressed by 1+1, 1:1 or M:N link protectionSet of links/nodes are averted by rings, planned mesh network

!! For proper use of planned resources use For proper use of planned resources use ““capabilitycapability”” of the Risk of the Risk DomainDomain

Reachability informationLinks have capabilities: 10 Mbps/100 Mbps, Encoding etc.Domain’s have capabilities:

Topology: Mesh, Ring (Bi-directional, Uni-Directional)Protection: 1+1, 1:1, 1:NOthers: All optical …


SRG SRG –– Inclusive constraintsInclusive constraints

Observation 2: Use a risk domain because of its capabilityObservation 2: Use a risk domain because of its capability((Inclusive constraintsInclusive constraints))

SRLG only provides exclusion constraintsSRG provides both Inclusive and Exclusive constraints

For example following types of constraint specifications are For example following types of constraint specifications are possiblepossible

Use the same ring for both the primary and secondary pathsDo not establish a secondary path through a protected domainProvide only domains that have certain level of risk protection


SRG SRG –– ScalabilityScalability

Observation 3: SRG notion provides scalabilityObservation 3: SRG notion provides scalabilitySRLG on trans-continental link (N >> 1)SRG set of SRLG (or a sequence)Link, Fibers, Ducts, Transport equipment, Nodes, COs# of TLVs, Diverse path computation – NOT scalable

! “Summarize” capability per risk domain


SRG SRG –– Topology representationTopology representation

Mesh Topology

AB

C

L2

L3

L1 A

C

B

Ring Topology

L2

L3

AB

C L3

L2

L1RL1

RL3

RL2

BL1RL2

Node BLink 1Risk Link 2

Legend:Note: A, B, Cmay be clientlayers to the intermediate nodeswhich constitute RLs.


Diversion Diversion –– Packet Packet vs vs Transport networksTransport networks

CategoryCategory Packet networksPacket networks Transport networksTransport networksInherent Not supported Supported (using rings etc.)protection

Topology Only mesh Mesh, ring, and mesh-ringinterconnects

Sub-layers of Single layer Multiple layersconnectionsCapability Only to link Link, node and domainassignment

Inclusive None Link, node, SRLG, amd SRGconstraints diversity

Exclusive Link, node, SRLG Link, node and SRGConstraintsPath Only strict explicit Strict and loose explicit pathscomputation paths


OutlineOutline



SRG applicationsSRG applications

Business applications Business applications Preferred quality circuit provisioningPreferably routed circuit provisioningProtected path provisioning

Mechanisms applicable toMechanisms applicable toMulti-layer networks

server layer topology capabilityTiered networks

Single or multiple administrative domainsPeer-to-peer or overlay control planes

With the following in mindWith the following in mindReduce the TE information distributed path computationOthers


What changed in applications?What changed in applications?

Before: Failure safe path provisioningBefore: Failure safe path provisioningThis is what we are doing now.

Link, Node, SRLG/SRG diverse paths

Now: Preferred quality circuit provisioningNow: Preferred quality circuit provisioningNeed to know and hence should propagate (routing)

Inclusive resource listExclusive resource listPath quality list


Business applicationsBusiness applications

Protected circuit provisioning Protected circuit provisioning Diversity specification

Preferably routed circuit provisioningPreferably routed circuit provisioningCustomers (or client layers) can specify the preferencesCustomers (or client layers) will have abstract representation of the provider topology

Preferred quality circuit provisioning Preferred quality circuit provisioning 5-9s or 6-9s availability


SRG applications SRG applications -- Risk AssessmentRisk Assessment

SRG’s SRG’s are helpful not only in finding diverse paths but also in are helpful not only in finding diverse paths but also in quantifying the risks of a given pathquantifying the risks of a given pathRisk Risk ≈≈ AvailabilityAvailabilityE.g., A, B, C are 99% available E.g., A, B, C are 99% available

Risk (Path ABC) = Risk A × Risk B × Risk C = 97%

A B C


OutlineOutline



SRG example SRG example -- ConfigurationConfiguration

SRG = 10

SRG = 12

SRG = 11

A

B

C

D H

EF

G L

MO

K

N

SRG = 1

I

J

Domain boundary

- Domain boundary configuration- Domain to SRG allocation- SRG capability allocation- Capability <-> reliability parameter allocation- Domain preference policy allocation

Single service provider

Optional


SRG example SRG example –– Info disseminationInfo dissemination

SRG = 10

SRG = 12

SRG = 11

A

B

C

D H

EF

G L

MO

K

N

SRG = 1

I

J

Same service provider

in topology databaseB. Node A’s SRG 11 representation

G

J

L

L3

L2

L1

RL1

RL3

RL2

L1

L2

L3

Topology and TE information dissemination

Topology database

TE database

RL2 Risk Link 2

L1 Link 1

G Node G

SRG Capabilities:- a, b, c

RL1 Capabilities:- a = n, b = m, c = o

RL2 Capabilities:- ...

RL3 Capabilities:- ...

C. Node A’s SRG 11 representation in TE database

A. Routing in a multi -domaintransport network


SRG example SRG example –– Path computationPath computation

SRG = 10

SRG = 12

SRG = 11

A

B

C

D H

EF

G L

MO

K

N

Loose segmentsStrict segment

SRG = 1

I

J

Request tosetup a pathbetween <A, O>

path Computed between nodes A and O


OutlineOutline



ConclusionsConclusions

Introduced concepts of Introduced concepts of Domain (or risk domain)SRG and its capabilities

Extend the current protocols toExtend the current protocols toDefine per domain capabilities (protection etc.)

Link protection (present)Define inclusive constraints

Exclusive constraints (present)Provide risk assessment to a path

Not possible with present extensionsSummarize “some” capabilities across areas

No inter-area solution yetNote: Not every TE parameter is summarizable

Discussed realization of new servicesDiscussed realization of new services


ReferencesReferences

TETERequirements for Traffic Engineering Over MPLS – RFC2702Network hierarchy and multi-layer survivability, draft-ietf-tewg-restore-hierarchy-01.txtRouting, Signaling, and Others for transport networks –http://www.ietf.org/html.charters/ccamp-charter.html

SRG ReferencesSRG ReferencesInter domain routing with SRG, draft-many-ccamp-srg-01.txt“Achieving Diversity in Optical Networks Using Shared Risk Groups,” http://www.cs.odu.edu/~sudheer/technical/papers/journal/SRGPaper.pdf

Updated/extended version Updated/extended version ––http://www.cs.odu.edu/~sudheer/technical/presentations/MPLSWorldhttp://www.cs.odu.edu/~sudheer/technical/presentations/MPLSWorldCongress2002.SRG.Congress2002.SRG.pdfpdf


Questions and AnswersQuestions and Answers

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