mpls history piotr pacyna v2 - it.uc3m.esppacyna/switching/lecture/slides/mpls_history_1pps.pdfPiotr...

David David LarrabeitiLarrabeitiPiotrPiotr PacynaPacyna

Dpto. de IngenierDpto. de Ingenieríía Telema TelemááticaticaUniversidad Carlos III de MadridUniversidad Carlos III de Madrid

OriginsOrigins ofof MPLSMPLS

MPLS 1Departamento de Ingeniería Telemática

Programme authors and contributors

Lecturers (Spanish course):

David Larrabeiti López

José Félix Kukielka

Supporting lecturers (English course):

Jorg Diederich

Huw Oliver

Piotr Pacyna


Before MPLS: Integration of IP and ATM (Server-Based)

Initial solutions:LAN Emulation (ATM Forum, 1995, 1997)CLIP: Classical IP over ATM (IETF, 1994)

Partial Improvements:NHRP: Hop-by-hop address resolution for short-cut VCs (IETF, 1996)MARS: Multicast address resolution (IETF, 1996)

Integration:MPOA: Multiprotocol over ATM (ATM Forum, 1997, 1999)

Server-based schemes: Need new protocolsServer: Potential single points of failure

Need redundant serversProtocols to ensure consistency among servers

Complexity + High costs


Before MPLS: Integration of IP and ATM (Overlay Approach)

Overlay approach:Two independent schemes (one ATM and one IP)

For addressing, routing, resource reservation,…

ATM network transparent to IP routersNeed to interconnect all routers directly using VCs

Else: Need another router in the network potential bottleneck

Full mesh structure in the ATM network: O(N2) SVCs

Insufficient scalability

Label Switching: CombineFunctionality of a router (IP) Advantages of a switch (ATM)


Overlay Network: Scalability Problem

Number of SVCs between routers growing faster than number of

routers

Signaling eventually becomes bottleneck

Router

Router

Router Router

Router

Router

Router

Switch Switch

SwitchSwitch

VC

VC

VC

VC

VC

VC

VC

VC

VC

VC

VC

VC


Disadvantages of the IP/ATM integrationapproach

Based on servers=> protocols=> single points of failure => redundancy, synchronisation

ComplexityOVERLAY Approach

2 independent schemes forAddresses, routing, reservations, logical IP topology/physicalATM

Lack of scalabilityFULL MESH

O(N2) SVCs; O(N3) messages after link failureSignalling is a bottleneck

¿is it possible to combine the advantages of IP and ATM?¿is it possible to have devices with the functionality of a

routes and the benefits of a switch?


Label Switching: Objectives

Higher performance and scalabilityExponential growth of the Internet (traffic + number of nodes)

Lower complexity and higher robustnessE.g. in the overlay model: two control planes

ATM: PNNI, UNI, ...

IP: OSPF, BGP,...Complex mapping necessary better avoid this

Achieve lower costs per router / switch + higher robustnessEnable evolution of control mechanisms:

Fixed forwarding scheme (e.g. in hardware)Exchangeable control scheme (e.g. routing protocol)Very important objective (but not so well-known)

Integrate IP routers and switches (mainly ATM)Use ATM switching technology (others possible)Re-use IP control plane technology (very wide-spread)

HistoryHistory


Initial Vendor Proposals

Cell Switch Router, Toshiba (1994)First scheme to control ATM switches by IP protocolsAvoid using ATM signaling and mapping functions to reduce complexity

IP Switching, Ipsilon (1996)Tag Switching, Cisco

Different from IP Switching and cell switch routersBasically the basis for MPLS

Aggregate Router-Based IP Switching (ARIS), IBMSimilar to Tag Switching

Differences in the way to assign and maintain labels

Standardization in the IETF:MPLS: MultiProtocol Label SwitchingPushed by Cisco (Tag Switching) and IBM (ARIS)


IP switching

Ipsilon, 1995 RFC1953, 1954, 1987

IP switch: ATM switch without ATM routingprotocol, without signalling and with IP routingcontrol

GSMP: General SwitchManagement Protocol

IFMP: Ipsilon FlowManagement Protocol

ATMSwitch

PC with Router-Based Software

IP

ATM

IFMP

GSMP

LLC/SNAP+AAL5


Control Plane in Nodes

IP

ATMARP MARS NHRP

Q.2931

ATM

IP

ATM

IFMP

UNI/PNNI

CLIP/MARS IPSILON

GSMP

LLC/SNAP+AAL5

LLC/SNAP+AAL5


IP Switching: Basic Function

Initially:All traffic between IP switches sent over a default VC

Routing controlled by the switch controller

Each controller:Detects “sustained” flows locally

Assigns a VPI/VCI to the flow (the label)

Tells the neighbor about the label

IFMP: Ipsilon Flow Management Protocol

Move from IP-based forwarding to switched forwarding step-by-step (i.e. IP Switch by IP Switch)


IP Switching: Normal Forwarding

Controller

ATMswitch

Previousnode

Nextnode

DefaultVPI/VCI

Flow selection

Send certain packetswith new VPI/VCI

IFMP


IP Switching: Direct Forwarding

Controller

ATMPrevious

nodeNextnode

DefaultVPI/VCI

Selection ofthe same flow

Send these packetswith new VPI/VCI

IFMP


IP Switching: Flow Detection

Discussion:IP Switching is a simple solution

Problem:Which flows shall be switched?

Solution: Data-drivenLook at the application layer protocol

Candidates: FTP, telnet, HTTP, audio and video

Cross-layer interaction to improve performance

Is that efficient?According to Ipsilon: Yes

80% of the packets and 90% of all bytes successfully switched


Toshiba CSR RFC2098, 2129

Cell Switch Router, Toshiba (1994)Detection of sustained flows + Label assignment(FANP)

Preconfigured short cuts

Objective:LIS-LIS communications

Works over conventional ATM network (only)Implements PNNI, ATM signaling

Interconnection with MPOA, CLIP, …


Aggregate Route-Based IP Switching (ARIS)

Concept of aggregationsAggregate routes on their way to the destination

ATM: VC-merging

Concept of ordered control

Assign labels in a coordinated way

More details to follow...

EGRESS point


MPLS

Standardization in the IETFBOF session December 1996 initiated WG

Main problem: Different label switching approaches not

interoperable without standardizationIndustry initiative

Integrate the existing proposalsBasically Tag Switching from Cisco and ARIS from IBM

MultiprotocolIndependent of layers below label switching

Ethernet, ATM, FDDI, FR, PPP, …

SDH, optical switching...

MPLS forwarding independent from layers above

IPv4, IPv6, IPX, AppleTalk, …Basically focused on IP


References

[1] MPLS Technology and Applications. Bruce Davie, Yakov Rekhter. Morgan Kaufmann. 2000.

[2] Transparencias del tutorial de MPLS de Nortel Networks impartidopor Ricardo Borrajo (profesor asociado) en la Universidad Carlos III de Madrid.

[3] Eric Osborne, Ajay Simha. Traffic engineering with MPLS. 1ªEdición. Cisco Press , 2002.

[4] MPLS-based VPNs. Tomsu, Wieser. 2002.

[5] RFC 3031. Multiprotocol Label Switching Architecture.

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