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Generalized Multiprotocol Label Switching

Konstantinos LizosPhD Student – klizos@ifi.uio.no

Spring 2015

University of Oslo (UiO)The Faculty of Mathematics and Natural SciencesDepartment of InformaticsCourse INF9050 - http://www.uio.no/studier/emner/matnat/ifi/INF9050

Materials mainly extracted by [1] A. Banerjee, J. Drake, J. Lang and B. Turner, “GMPLS: An Overview of Signaling Enhancements and Recovery Techniques”

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Principles of MPLS

• Constraint-based routing as opposed to best effort internet service

• MPLS addition : connectivity abstraction (end-to-end)

• Explicitly routed point-to-point path as opposed to multipoint to point (unicast) path in conventional IP networks

MPLS Limitations

• MPLS’s inability to establish bidirectional connections in a single request and the absence of mechanisms to account for protection bandwidth in lower-priority traffic.

• A link or node failure along the routes of established service connections can only be handled locally or along the nodes of the path

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Evolution of GMPLS

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MPLambaS Proposal

GMPLS

Extensions to IP signaling RSVP-TE & CRLDP

Extensions to IP Routing OSPF-TE & ISIS-TE

IETF TE

Working Group

IETF MPLS

Working Group

Requirements for TE over MPLS

Origins

• Traces back to multi-protocol lambda switching (MPλS) originally proposed by Awduche and Rekhter (1999)

• GMPLS has generalized the MPλS concept, so that the same control plane concepts can be used in other switched transport technologies, such as TDM, optical as well as cell switched networks.

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GMPLS extends the concept of label

1) in a packet-switched network, a label represents a short tag attached to a packet.

2) in a TDM network, a label represents a time slot

3) in a wavelength-switched network, a label represents a wavelength

4) In a fiber-switched network, a label represents a fiber.

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GMPLS Interface Expansion

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PSC

Expand MPLS functionality to sustain extra interfaces in addition to packet switch

Fiber-Switch Capable (FSC)Packet Switch Capable (PSC)

Router/ATM Switch/Frame Reply Switch

Time Division Multiplexing Capable (TDMC)

SONET/SDH ADM/Digital Crossconnects

Lambda Switch Capable (LSC))All Optιcal ADM or Optical Crossconnects (OXC)

LSPs of diverse interfaces can be nested inside LSPs of diverse interfaces can be nested inside anotheranother

LSC

TDMC

TDMCLSC

FSC

Copyright ® Lizos

Techniques by GMPLS devices

• Protection and restoration techniques used by GMPLS devices– Fault isolation– Fault localization– Fault notification– Fault mitigation

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Signaling

• GMPLS requires that an LSP starts and ends on similar types of devices.

• MPLS is designed so that the control plane is logically separate from data plane

• GMPLS extends this concept, by allowing the control plane to be physically diverse from the associated data plane.

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Hierarchical LSPs

• GMPLS supports the concept of hierarchical LSPs, which occurs when an LSP is tunneled inside an existing higher-order LSP so that the preexisting LSP serves as a link along the path of the new LSP.

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R10

Nested LSP

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Fiber LSP4

λ LSP3

Time slot (TDM) LSP2

Packet LSP1

LSP4LSP3LSP2LSP1

500 m from a 500 m from a Gigabit EnetGigabit Enet

OC-12cOC-12c

OC-192OC-192

FiberFiber

Router acting Router acting

as an IP LSRas an IP LSR

SONET SONET switch/mixswitch/mix

Optical OEO Optical OEO switchswitch

Photonic Photonic switchswitch

O

R

S

P

P4 P5 P6O3 O7S2

S8

R1 R9R0

Process of creating an LSP

• Assumption: RSVP-TE signaling extension (defined in GMPLS) assumes required bandwidth is available on each of the links

• Residual bandwidth available in LSP hierarchy is advertised by the Interior Gateway Routing Protocols (IGP) – R1 announces packet-switch capable link

(PSC)– S2 announces time division multiplex (TDM)

link– O3 announces lambda-switch capable (LSC)

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Creating an LSP

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TimelineTimelineR0 R1 S2 O3 P4 P5 P6 O7 S8 R9 R10

Path 1

Path 2

Path 3

Path 4

Resv 4LSP4

completesResv 3

LSP3 completes

LSP2 completes

LSP1 completes

Resv 2

Resv 1

Bidirectional LSP Setup

• Bidirectional optical LSPs (or lightpaths) is supported by GMPLS

• Supposedly, both directions of such LSPs have the same TE requirements

• Initiator: starting establishing an LSP• Terminator: LSP destination node• Bidirectional LSP: only one initiator and one

terminator• MPLS defines unidirectional LSP. To attain

bidirectional LSP setup, two independent LSPs must be formed in opposite directions.

Disadvantages: I) high latency, II) increased control overhead, III) P(A,B)=P(A)P(B)min{P(A),P(B)}

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Notify messages• Central requirement: response to network failures must

be quick and decisions must be made intelligently• A node passing transit connections can notify node(s)

responsible for restoring connections when failures occur.

• Notify message has been added to RSVP-TE for GMPLS to convey to non-adjacent nodes of LSP-related failures.

Applications for Notify message Inform about a degraded link (control plane failed, data

plane still functional*)* Control plane failures may limit management features

but doesn’t always justify termination of an LSP.

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GMPLS Protection and Restoration Techniques

• Key feature for constructing a common control plane involves coordination among signaling, routing and link management protocols to enable intelligent fault management consisting of

I) Detection, II) LocalizationIII) Notification and IV) Mitigation

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Achieving the goal for protection and restoration

Protection and restoration can traditionally been addressed by using two techniques:Path switching: failure is addressed at the path endpoints (i.e. the path initiating and terminating nodes)

Path protection: secondary protection paths are preallocated

Path restoration: connections are rerouted, either dynamically (could have precalculated paths)

Line Switching: failure is addressed at the transit node where the failure is detected

Span protection: traffic is switched to an alternate parallel channel or link connecting the same two nodes

Line restoration: traffic is switched to an alternative route between the two nodes

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Protection mechanisms

In summary, protection mechanisms are1+1 protection: payload is transmitted simultaneously over two disjoint paths (selector chooses best signal)M:N protection: M predesignated backup paths are shared between N primary paths1:N protection: 1 preallocated backup path is shared among N primary paths1:1 protection: 1 dedicated backup path is preallocated for 1 primary path

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Restoration mechanisms

• Typically takes more time to react & resolve failures by switching to alter-nate paths, due to dynamic nature.

• Restoration can be implemented both at the source or an intermediate node, once the responsible node has been notified.

• Failure notification is performed using notify procedures or standard error messages

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Conclusions

• GMPLS provides the necessary linka-ge between the IP and photonic layers, allowing interoperable, scalab-le, parallel and cohesive evolution of networks in the IP and photonic dimensions.

• Basically, GMPLS resolves the main problem of scalability by segregating the transport network from the data.

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Conclusions / Q & A

• New traffic flows and proliferation of mobile terminals require robust high-capacity structures that support fast provisioning, other than voice.

• GMPLS-based products can be applied in existing networks to decrease costs without impacting service quality.

• Flexible M:N protection and restoration capabilities of GMPLS allow efficient addressing of network survivability.

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References

• A. Banerjee, J. Drake, J. Lang and B. Turner, “GMPLS: An Overview of Signaling Enhancements and Recovery Techniques”, IEEE Communications Magazine, Vol:39, Issue:7, p.p: 144-151, doi: 10.1109/35.933450

• Daniel O. Awduche, Bijan Jabbari, "Internet traffic engineering using multi-protocol label switching (MPLS)", Computer Networks 40 (2002) 111-129

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Types of switches

Multiplexing technique on

data-plane linksAdmissioncontrol in control plane?

Circuit switch (CS)- position based (port, time, lambda)

Packet switch (PS)- header based

Connectionless (CL) - no admission control

Not an option

e.g., Ethernet

Connection-oriented (CO)- admission control

e.g., telephoneSONET WDM

Virtual-circuit e.g., MPLS, ATM

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Types of networks

Support function

Networktype

Addressing(in data or control plane?)

Routing Signaling

Connectionless (CL)

Data plane

Circuit Switched (CS)

Control plane

Virtual circuit (VC)

Control plane

Connection-oriented