june 4, 2003carleton university & eiongmpls - 1 gmpls generalized multiprotocol label switching...

June 4, 2003Carleton University & EION GMPLS - 1

GMPLS

Generalized Multiprotocol Label Switching

Vijay MahendranSumita Ponnuchamy

Christy Gnanapragasam


Outline

• Background– Terminology– Optical Network Architectures– MPLS

• GMPLS

• Signaling– General Signaling– CR-LDP/RSVP


Terminology• MPLS – Multi-Protocol Label Switching• GMPLS – Generalized MPLS• LSR – Label Switched Router• LER – Label Edge Router• LSP – Label Switched Path• RSVP-TE – Resource Reservation Protocol with Engineering• CR-LDP – Constraint Based Label Distribution• OSPF – Open Shortest Path First• IS-IS – Intermediate System to Intermediate• UNI – User-Network Interface• NNI – Network-Network Interface• DWDM – Dense Wavelength Division Multiplexing• OXC – Optical Cross-Connect• LMP – Link Management Protocol


?

Optical Network Architectures• Overlay model

–Two independent control planes

• Optical domain & IP/MPLS routing

–Router is client of optical domain

–Optical topology invisible to routers

• Peer model–Single integrated control plane

–Router and optical switches are peers

–Optical topology is visible to routers

• Hybrid model–Multi admin domain support (overlay)

–Multiple technologies within domain (peer) UNI

Peer


MPLS

• Speed of Layer 2 switching in Layer 3• AIM : Establish the Forwarding Table

– Link state routing protocols• Exchange network topology information for path

selection• OSPF-TE, IS-IS-TE

– Signaling/Label distribution protocols:• Set up LSP (Label Switched Path)• LDP, RSVP-TE, CR-LDP

Control:IP Router Software

Control:IP Router Software

Forwarding:Longest-match Lookup

Control:ATM Forum Software

Forwarding:Label Swapping

IP Router MPLS ATM Switch

Forwarding:Label Swapping


1a. Routing protocols (e.g. OSPF-TE, IS-IS-TE) exchange reachability to destination networks

1b. Label Distribution Protocol (LDP) establishes label mappings to destination network

2. Ingress LER receives packet and “label”s packets

IP

IP 10

3. LSR forwards packets using label swapping

IP 20IP 40

4. LER at egress removes label and delivers packet

IP

MPLS Operation


GMPLS• Extend MPLS to cover the Optical Domain

– Packet Switch Capable (PSC)– Layer 2 Switch Capable (L2SC)– Time Division Multiplexing Capable (TDMC)– Lambda Switch Capable (LSC)– Fiber Switch Capable (FSC)

• A common control plane– Support multiple types of traffic (ATM, IP, SONET and etc.)– Support both peer and overlay models– Support multi-vendors– Perform fast provisioning


• GMPLS is deployed from MPLS– Apply MPLS control plane techniques to optical switches – IP routing algorithms to manage light paths in an optical

network

• GMPLS made some modifications on MPLS– Separation of Control and Data planes– Support multiple interface– Enable nesting of different interfaces

FSCLSC

LSC

TDMC

TDMC

PSC


Key Extension To MPLS• Label encoded as timeslots, wavelengths,

position in real world• LSP start & end on similar interfaces• Suggested Labels by upstream node• Label restrictions• Bi-directional LSPs• Support rapid failure notification• BW allocation in discrete time• Extended payload encoding


GMPLS Control Plane

• Extension of MPLS control plane– GMPLS extends OSPF-TE and IS-IS-TE for routing– GMPLS extends RSVP-TE and CR-LDP for signaling– Control Channels in-band or out-of-band– LMP- Link Management Protocol

• Extension to MPLS-TE


GMPLS Scalability• Unnumbered Links

– No IP

– Specify unnumbered links: local ID• Exchange local ID (signaling protocol)

– Carry TE info about unnumbered links• new sub-TLVs


Bundled Link 2

Bundled Link 1

• Multiple parallel links between nodes can be advertised as a single link into the IGP

– Enhances IGP and traffic engineering scalability

• Component links must have the same– Link type– Traffic engineering metric– Set of resource classes– Link multiplex capability (packet, TDM, λ, port)

• Max BW request BW of a component link

• Link granularity can be as small as a λ

Link Bundling


Link Management• Procedures between LSRs:

– Management– Verification– Property Correlation– Fault Management


Generalized Signaling• Allow establishments of PATHs

– ATM/FR labeled paths– Time division multiplexed paths– Frequency division multiplexed paths– Space division multiplexed paths

• GMPLS Signaling– CR-LDP and RSVP-TE

• Extends based functions• Add functionalities


Signaling Protocols• Label Distribution Protocol (LDP) establishes label-

to-destination network mappings• CR-LDP extended from LDP to for G/MPLS• RSVP - QoS reservations between hosts• RSVP Extensions for GMPLS

– Concept of labels and LSPs Explicit routes– LSP attributes

• Setup and Holding priorities


GMPLS Features

• New generic label request format• Labels for TDM/LSC/FSC interfaces• Specific traffic parameters per technology• Bi-directional LSP establishments• Ingress/Egress binding


LSP Request

• Send PATH/Label Request downstream– Type of LSP– Payload type– BW encoding

• SENDER_TSPEC: RSVP-TE• Traffic Parameter TLV: CR-LDP

– Protection– Bi-directional LSP support

• Specify upstream label

– Suggested labels


Response for LSP Request

• Resv/Label Mapping message sent by the downstream LSR– Generalized Label object

• Several Generalized Labels– List of labels: SONET/SDH


GMPLS - SignalingGeneralized Label Request

– the encoding of label requested

– the type of switching required

• Generalized Label– In addition to representing a packet – a label can represent

• a number of time slots • a wavelength • a set of contiguous wavelengths (waveband)• Etc.


Enhancements to Signaling• Suggested Label

– Label suggestion from upstream node– Reduction in setup latency– Important for restoration

• Restricted Labels– provide upstream node with control over chosen labels– limit the choice of labels to the downstream node

• Bi-directional LSP– demand for bidirectional LSPs in support of TDM and

Lambda switching– Both directions have same traffic engineering requirements


Suggested Label = Program Switch X

Suggested Label =

Reserved Label = Reserved Label =

Make sure the programming request has completed

Request

Program Switch X

Request

Map Label = Map Label =

No suggested label with suggested label

Suggested label• Problem:

•it takes time for the optical switch to program switch Long setup time

•Solution:•Each LSR selects a label (Suggested Label) and signals this label to downstream LSR, and start program its switch.•reduce LSP setup overhead


Suggested Label = Upstream Label = a

Suggested Label = Upstream Label = b

Reserved Label = Reserved Label = a b

Bi-Directional LSP setup•Problem:

• How to set up bi-directional LSP?•Solution:

• Set up 2 uni-directional LSP• Signaling overhead• End points coordination

• One single message exchange for one bi-directional LSP• Upstream label


Enhancements to Signaling

• Notification– Notify message added to RSVP-TE for GMPLS– This message for link failures

• Nested LSPs – allows the system to scale by building a forward hierarchy– At the top of hierarchy are FSC interfaces, then LSC, TDM, and PSC interfaces

• Protection– protection information in a new object, specifying the LSP is the primary or secondary one – the desired protection type


LSP Nesting


GMPLS – Nested Signaling


Protection• Link protection

– Protection capability– Attributes

• None, 1:1, 1+1, 1:N, or ring• Priority for a working channel

1:1 Protection

Working

Protection

1:N Protection

Working

Protection


CR-LDP/RSVP-TE


RSVP-TE Details• RSVP-TE is an extension of “classical” RSVP• Runs directly over IP• Uses Path messages (= Label Request) and Resv messages (= Label Mapping)• Extends classical RSVP with new objects

(= (Type,length,value) TLVs) for these messages• Explicit Route Object (ERO) contains hops


CR-LDP details• CR-LDP is an extension to LDP• Like LDP, runs over TCP• Uses existing LDP messages, but defines additional TLVs for the messages• LSR Discovery

–Multicast HELLO to well-known UDP port on “all routers on this subnet” multicast group–Can also send to configured IP addresses–Make TCP connection upon response


Common features• Operate in (Downstream-on-Demand, Conservative, Ordered) mode• Features:

–Explicit route–QoS specification–LSP preemption–LSP modification

• LDP sets up LSPs automatically, while CR-LDP and RSVP-TE typically require some sort of external intervention


CR-LDP and RSVP-TE• Used to set up point-to-point LSPs• LSPs can follow any path• Can specify QoS parameters for LSP• Useful for:

–Traffic Engineering of Public Internet traffic–Traffic Engineering of VPN tunnels–Automatic Setup of Light Paths in Automatically

Switched Optical Networks (ASON)


#963

#14

#99

#311

#311

#311

#462

D

#311

D

#963D

#14 D

#99D

#216

D

#612 D

#5 D

Unsolicited Mode


#963

#14

#99

#311

#311

#311

#462

D

#311

D

#963D#14 D

#99D

#216

D

#612 D

#5 D

D?

D? D?D?

D?

D?

D?

D?

On Demand Mode


#462

D

#311

D

#963D

#14 D

#99D

#216

D

#612 D

#5 D

#422D

#622 D

These labels are kept in case they are needed after a failure.

LIBERAL RETENTION


#462

D

#311

D

#963D

#14 D

#99D

#216

D

#612 D

#5 D

#422D

#622 D

These labels are released the moment they are received.

CONSERVATIVE RETENTION


POP

10.1.1.1

10.1.1.4

10.1.1.3

Explicit route

10.1.1.7 strict10.1.1.6 strict10.1.1.2 loose10.1.1.1 loose

Strict hopLSP takes direct route to 10.1.1.7

Loose hopLSP takes shortestpath to 10.1.1.210.1.1.2

10.1.1.6

10.1.1.7

10.1.1.5

Explicit route example


ER LSP - advantages

•Operator has routing flexibility (policy-based, QoS-based)

•Can use routes other than shortest path

•Can compute routes based on constraints in exactly the same manner as ATM based on distributed topology database.(traffic engineering)


#216

#14

#462

#972A

B

C

Route={A,B,C}

PREEMPTION


RSVP-TE Vs. CR-LDP• RSVP-TE uses raw IP, while CR-LDP uses TCP to

distribute labels and UDP to discover neighbors

• High Availability: – RSVP-TE lends itself well to a system that must survive

hardware failure or online software updates. – CR-LDP assumes reliable delivery of messages and so is

not well placed to survive failover

• RSVP-TE is a soft state protocol, needing periodically refreshing

• Failure notification: only RSVP-TE provides failure notification, not CR-LDP!


TIME

NODEA

NODEB

NODEA

NODEB

RSVP LDP/CR-LDP

REQUEST PATH

PATH

PATH

PATH

PATH

MAPPINGRESV

RESV

RESV

RESV

RESV

THAT’S ALL!!

FOREVER!!

RSVP Vs. CR-LDP


RSVP-TE:Refresh reduction• Each Path and Resv message must be

refreshed• In a network with many LSPs, this requires

lots of messages• Hence the Refresh Reduction Extension• This allows a router to send a single

compact message that refreshes lots of LSPs at once


Summary

• GMPLS is an extension of MPLS:• PSC• TDMC• LSC• FSC

• GMPLS Signaling • Establish Forwarding State • Label Distribution

• CR-LDP/RSVP- two signaling protocols• essentially the same functionality


References• Generalized Multi-Protocol Label Switching Architecture

(draft-ietf-ccamp-gmpls-architecture-07.txt)

• Ayan Banerjee, John Drake, Jonathan P. Lang, Brad Turner, Kireeti Kompella, and Yakov Rekhter, “Generalized Multiprotocol Label Switching: An Overview of Routing and Management Enhancements” IEEE Communications Magazine, January 2001.

• Mark J. Francisco “Generalized Multiprotocol Switching” Advanced Optical Networks Laboratory Carleton University January, 2002

• Generalized MPLS - Generalized MPLS -Signaling Functional Signaling Functional Description (draft-ashwoodgeneralized-mpls-signaling-00.txt)

• Gavin Gandhi “Generalized MultiProtocol Label Switching”, University of Southern California. Available at http://www-classes.usc.edu/engr/ee-s/650/Lecture%20note/GMPLS-Presentation%20by%20Gavin.pdf


• Ayan Banerjee, John Drake, Jonathan Lang, Brad Turner, Daniel Awduche, Lou Berger, Kireeti Kompella, Yakov Rekhter, “ Generalized Multiprotocol Label Switching: An Overview of Signaling Enhancements and Recovery Techniques”, IEEE Communications Magazine • July 2001.

• Li Yin, “MPLS and GMPLS” Available at www.cs.berkeley.edu/~randy/Courses/cs294.s02/MPLS.ppt

• Peter Ashwood-Smith and Bilel Jamoussi, “MPLS Tutorial and Operational Experiences”, October, 1999. Available at http://www.nanog.org/mtg-9910/ppt/peter.ppt

• Packets & Photons: The Emerging Two Layer Network”, October 2001. Available at http://www.nanog.org/mtg-0110/ppt/shepherd/

• RFCs : 3471,3472, and 3473


Thank You

june 4, 2003carleton university & eiongmpls - 1 gmpls generalized multiprotocol label switching...

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