gmpls overview - snummlab.snu.ac.kr/links/hsn/workshop/hsn2002/documents/ix_1.pdfmultimedia...

1

GMPLS OverviewGeneralized MPLS

Hanyang Univ정재일

( [email protected] )

Multimedia Networking Lab 2

OutlineGMPLS Overview

Draft-ietf-ccamp-gmpls-architecture-00.txt

GMPLS IGP ExtensionDraft-ietf-ccamp-ospf-gmpls-extensions-00.txtDraft-ietf-ccamp-isis-gmpls-extensions-04.txt

GMPLS Signaling ExtensionDraft-ietf-mpls-generalized-signaling-06.txtDraft-ietf-mpls-generalized-rsvp-te-05.txtDraft-ietf-mpls-generalized-cr-ldp-04.txt

GMPLS LMPDraft-ietf-mpls-lmp-02.txtDraft-ieft-mpls-lsp-hierarchy-02.txtDraft-ietf-mpls-bundle-00.txt


AbstractGMPLS Architecture

time-division(e.g. SDH/SONET, PDH, G.709)

Wavelength(lambdas)

Spatial Switch(e.g. Incoming port or fiber

to outgoing port of fiber

MPLS

GMPLS


AbstractTraditional MPLS supports packet switchingFuture data and transmission Networks’ Elements

Router Switch DWDM systems ADM PXC(OXC)

GMPLS

Dynamically Provision Resources

Network Survivabilityusing protection

and restoration techniques


GMPLS GoalsA single network-wide control plane to

Distribute optical transport network topology stateSet up optical channel trails

Support traffic engineering functions and enable protection and restoration capabilitiesSimplify the integration of optical switches, optical transport, and label switching routersEnhances service provider revenues

New services creation, Faster provisioning, Operational efficiency


Multiple Switching TypesPacket-Switch Capable(PSC) interfaces

Routers(IP herder, MPLS shim header)

Time-Division Multiplex Capable(TDM) interfaces

SDH/SONET Cross-Connect, ADM

Lambda Switch Capable(LSC) interfacesWavelength

Fiber-Switch Capable(FSC) interfacesPhotonic Cross-Connect


Extends MPLS to support multiple switching types

Lambda Switching

Waveband switching Port Switching

TDM(SONET/SDH) Switching


Multiple Switching Types


Multiple Switching TypesA Circuit can be established only between, or through, interfaces of the same type.

e.g SDH circuit, Optical trail, Light path etc.In GMPLS all these circuit -> Label Switched Path

A hierarchy of LSPsNested LSP(LSP within LSP)Already available in traditional MPLSOn Same interface or between different interfaces

Same interfacee.g a lower order SDH/SONET LSP(VC-12) nested in a higher order SDH/SONET LSP(VC-4)

Different interfaceFSC > LSC> TDM > PSC


Extension of MPLS Control PlaneGMPLS

Extend control planes to support of the four classes of interfaces

GMPLS Building BlockThe Main Building Blocks

To build a consistent control plane for multiple switching layers.Different models can be applied : e.g.overlay, peer, augmented/integrated, A number of combinations are possible.


Extension of MPLS Control PlaneOverlay model

Two independent control planesIP/MPLS routingOptical domain routing

Router is client of optical domainOptical topology invisible to routersRouting protocol stress – scaling issuesSimilar to IP over ATM

Peer ModelSingle integrated control planeRouter and optical switches are peersOptical topology is visible to routersSimilar to IP/MPLS model

?


Extension of MPLS Control PlaneGMPLS can be summarized as follows

The Concepts of Generalized InterfaceA new Link Management Protocol(LMP)

To address issues related to link management in optical networks using photonic switches

Traffic Engineering EnhancementsEnhancements to OSPF/IS-IS

To advertise availability of optical resources in the networks(e.q. Generalized representation of various link types, bandwidth on wavelengths, link protection type, fiber identifiers)

Enhancements to RSVP-TE/CR-LDPTo allow a LSP to be explicitly specified across the optical core.

Scalability enhancementssuch as hierarchical LSP formation, Link Bundling


Key Difference(1)

MPLS-TE GMPLS

an intermix links(e.g. links between routers,

or ATM-LSRs, or between ATM-LSRs and routers)

including left box,timeslot, or wavelength or fiber

Start and end on a IP router Start and end on similar type of LSRs

bandwidth allocation in continuous spectrum

bandwidth allocation in discrete units

uni-directional support for bi-directional


Key Difference(2)GMPLS

Expected to have(much) fewer labels on non-PSC links than on PSC linksForwarding Adjacency(FA) mechanism

to improve bandwidth utilizationto aggregate forwarding stateallowing the number of required labels to be reduced

Allowing for a label to be suggested by an upstream node

to reduce setup latencyGMPLS with RSVP-TE supports an RSVP specific mechanism for rapid failure notification


Key Difference(3)An ingress or other upstream node may restrict the labels(Label Set) that may be used by an LSP along either a single hop or along the whole LSP pathConstraining Label Choice

Some switches cannot modify labels (lambdas)May want to restrict available resourcesAdvertise available lambdas using ‘Label Set’Label set is allowed to have just one member


GMPLS Scalability EnhancementGMPLS

The overall number of links in optical/TDM can be several orders of magnitude larger than that of an MPLS network -> Link BundlingIdentifying which port on a network element is connected to which port on a neighboring network element is also a major management burden and highly error-prone -> LMPFast fault detection and isolation, and fast failover to an alternate channel are needed -> LMPThe user data carried in the optical domain is transparently switched to increase the efficiency of the network -> LMP


GMPLS Scalability Enhancement

LSP Hierarchy


GMPLS Scalability EnhancementLSP Hierarchy

Aggregate multiple LSPs inside a bigger LSPIntermediate nodes see the external LSP onlyNo need to maintain forwarding states for each internal LSP

FA(Forwarding Adjacency)An LSR uses MPLS-TE procedures to create and maintain an LSPThe LSR may announce this LSP as a Traffic Engineering Link into IS-IS/OSPF.Such a link a “forwarding adjacency”We refer to the LSP as the FA-LSPthe bandwidth of FA-LSP must be at least as big as the LSP, but may be bigger if only discrete bandwidths are available for the FA-LSP


GMPLS Scalability EnhancementLink Bundling

When a pair of LSRs is connected by multiple links, it is possible to advertise several(or all) of these links as a single link into OSPF and/or IS-IS.To improve routing scalability by reducing the amount of information that has to be handled by OSPF and/or IS-ISAll component links in a bundle must begin and end on the same pair of LSRs, share common characteristics.


GMPLS Routing & Addressing model(1)

GMPLS is based on the IP routing and addressing model

IPv4 / IPv6 addresses are used to identify interfacestraditional (distributed) IP routing are also reused

IP addresses are used identify interfaces of IP hosts and routersmore generally to identify and PSC and non-PSC interfaces

IP routing protocols are usedfind routes for IP datagramsfind routes for non-PSC circuits by using a CSPF algorithm


GMPLS Routing & Addressing model(2)

Re-using existing IP routing protocols allows for non-PSC layers to take advantages of years for IP routing

Extensions for inter-domain(BGP) traffic engineering -> further studyExtensions for intra-domain traffic engineering used of link-state routing protocol -> OSPFOSPF--TE , ISTE , IS--ISIS--TETE

Optional mechanisms can be used to increase the scalability of the addressing and the routing ->Link bundling Link bundling


GMPLS TE Links1. Links that are non-PSC may yet have TE properties

OSPF adjacency cannot be brought up directly on such links

2. An LSP can be advertised as a point-to-point TE link in the routing protocol as a Forwarding Adjacency(FA)

Advertised TE link need no longer be between two OSPF neighbors

3. A number of links may be advertised as a single TE link for improved scalability Link Bundling

There is no longer a one-to-one association of a regular adjacency and a TE link


RSVP-TE / CR-LDP Extensions

PATH / REQUEST MessageGeneralized Label Request, Explicit RouteUpstream Label, Label Set, Suggested Label

RESV / MAPPING MessageGeneralized Label

SONET/SDHADM

SONET/SDHADM

RESV/MAPPINGRESV/MAPPING

PATH/REQUESTPATH/REQUEST


RSVP-TE / CR-LDP ExtensionsGeneralized Label Request

LSP Encoding Type: 8 bitsIndicates the type of technology

LSP Payload Type (G-PID): 16 bitsAn identifier of the client layer of LSP

Bandwidth EncodingGeneralized Label

Extends to include support of time-slot, wavelength, space division multiplexed positionOnly carries a single level of labelVariable length label parameter


RSVP-TE / CR-LDP ExtensionsWaveband Switching

Special case of lambda switchingSet of contiguous wavelengths which can be switched togetherAllow tighter separation of the individual wavelength

Suggested LabelPermits the upstream node to start configuring it’s hardware with the proposed label before the label is communicated by the downstream nodeCan reduce setup latency


RSVP-TE / CR-LDP ExtensionsLabel Set

Used to limit the label choices of a downstream node to a set of acceptable labels

Bi-directional LSP setupIndicated by the presence of an Upstream Label object/TLV in PATH/REQUEST message


RSVP-TE / CR-LDP ExtensionsNotification (RSVP-TE only)

Signaling extensions that modify error handling, enable expedited notification of failures and other events

Explicit Label ControlCan provide very detailed Explicit Routes, including the Label

Protection FlagsIndicate link related protection attributes of a requested LSP


Link BundlingBundled link 1

Bundled link 2

A pair of Label Switching Routers (LSRs) may be c connected by several (parallel) links.

From the MPLS Traffic Engineering point of view for r reasons of scalability it may be desirable to advertise a all these links as a single link into OSPF and/or IS-IS. = =>(link bundling)

Bundled link =A kind of Traffic Engineering link


Link BundlingReducing the amount of information is accomplished by performing Information aggregation/abstraction Restrictions on bundling:

All component links in a bundle must:Begin and end on the same pair of LSRsHave the same Link Type( Point-to-point or multi-access)Have the same Traffic Engineering metricHave the same Link Multiplex Capability


Link Management Protocol

Running between neighboring nodes

Four basic functions of LMPControl channel managementLink connectivity verificationLink property correlationFault isolationAuthentication

LMP LMP LMP LMP


Link Management ProtocolControl channel:

Bundled link has bi-directional control channels andcomponent links

Control channels consist of a primary controlchannel and back-up control channel(in the event of aprimary control channel failure)

Control channel can exchange:MPLS control-plane information(Such as link provisioning and fault isolation by using LMP)Path management and label distribution information(By using signaling protocol such as RSVP-TE or CR-LDP )Topology and state distribution information (By using traffic engineering extended protocols such as

OSPF and IS-IS)


Link Management ProtocolControl channel management:

To establish and maintain link connectivity between neighboring nodes Being done using Hello messages

Verifying link connectivity:The primary control channel:

Being first verified, and connectivity maintained, using the Hello protocol

Component link connectivity:Being verified by exchanging Ping-type Test messages over each of the component links specified in the bundled link


Link Management ProtocolLink property correlation:

A Link Summary message is transmitted in order to add component links to a bundled link, change Link Ids, or change a link's protection mechanism The Link Summary message can be exchanged at any time a link is UP

Fault localization:Fault detectionIf one or more component links fail between two nodes, a mechanism must be used to rapidly locate the failure so that appropriate protection/restoration mechanisms can be initiated

gmpls overview - snummlab.snu.ac.kr/links/hsn/workshop/hsn2002/documents/ix_1.pdfmultimedia...

Documents