Multiprotocol Label SwitchingRavikumar Pragada & Girish Srinivasan

The future of IP Backbone Technology

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OverviewNeed for MPLS MPLS Basics Benefits Label Switched Path Label Distribution Protocol Hierarchy in MPLS Explicit Routing Loop Detection Traffic Engineering Constraint Based Routing Tag Switching IP Switching

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Conventional IP Networks & RoutingClient networks are connected to backbone via

edge routers

LAN, PSTN, ADSL

Data packets are routed based on IP address and

other information in the header Functional components

Forwarding responsible for actual forwarding across a router consists of set of procedures to make forwarding decisions Control responsible for construction and maintenance of the forwarding table consists of routing protocols such as OSPF, BGP and PIM

Need for Multiprotocol Label Switching (MPLS)Forwarding function of a conventional router a capacity demanding procedure constitutes a bottle neck with increase in line speed MPLS simplifies forwarding function by

taking a totally different approach by introducing a connection oriented mechanism inside the connectionless IP networks

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Label SwitchingDecomposition of network layer routing into

control and forwarding components applicable Label switching forwarding component algorithm usesforwarding table label carried in the packet

What is a Label ? Short fixed length entity

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A Label Switched Path (LSP) is set up for each

MPLS Basics

route A LSP for a particular packet P is a sequence of routers,

for all i, 1< i < n: Ri transmits P to R[i+1] by means of a label

Edge routers analyze the IP header to decide which LSP to use add a corresponding local Label Switched Path Identifier, in the form of a label forward the packet to the next hop

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MPLS Basics contd.. Subsequent nodesjust forward the packet along the LSP simplify the forwarding function greatly increase performance and scalability

dramatically

New advanced functionality for QoS,

differentiated services can be introduced in the edge routers Backbone can focus on capacity and performance Routing information obtained using a common intra domain routing protocol such as OSPF

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B a si M o d e lfo r M P LS c N e tw o rkInternet

LER LSR LSR LER

IP

MPLS

LSR

LSR LER

MPLS IP

LSR = Label Switched Router LER = Label Edge Router8

MPLS BenefitsComparing MPLS with existing IP core and IP/ATM technologies, MPLS has many advantages and benefits: The performance characteristics of layer 2 networks The connectivity and network services of layer 3 networks Improves the price/performance of network layer routing Improved scalability

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MPLS Benefits contd..Improves the possibilities for traffic

engineering Supports the delivery of services with QoS guarantees Avoids need for coordination of IP and ATM address allocation and routing information

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Necessity of L3 ForwardingFor security To allow packet filtering at firewalls Requires examination of packet contents, including the IP header For forwarding at the initial router - used

when hosts dont do MPLS For Scalinglabels can provide

Forward on a finer granularity than the

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Carrying a LabelCertain link layer technologies can carrye.g ATM & Frame Relay

label as a part of their link layer header

Link layers that do not support labels in

their header carry them in a shim label header

Link layer Shim label Network header header layer header

Network layer data

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Establishing Label Switched PathLSPs are generated and maintained in a

distributed fashion Each LSR negotiates a label for each Forwarding Equivalence Class (FEC) with its upstream and downstream neighbors using a distribution method Label Information Base (LIB) - Result of negotiation

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LDP - TerminologyLabel Distribution Protocol (LDP) set of procedures by which LSRs establish LSPs mapping between network-layer routing information directly to data-link layer switched paths LDP peers: two LSRs which use LDP to exchange label/stream mapping information exchange known as LDP Session14

LDP Message ExchangeDiscovery messages - used to announce and

maintain the presence of an LSR Session messages - used to establish, maintain and terminate sessions between LDP peers Advertisement messages - used to create, change, and delete label mappings Notification messages - used to provide advisory information and to signal error information

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LD P M e ssa g e Fo rm a t0 1 2 3 01234567890123456789012345678901U Message Type Message ID Mandatory Optional Parameters Parameters Message Length

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LDP Protocol Data Units (PDUs)

LDP message exchanges are accomplished by sending LDP PDUs Each LDP PDU is an LDP header followed by LDP message The LDP header is:0V ersio n L P D

1

2P UL gth D en Id tifier en

3

01234567890123456789012345678901

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Forwarding Equivalence Class (FEC)Introduced in MPLS standards to denote

packet forwarding classes Comprises traffic

to a particular destination to destination with distinct service

requirements

Why FEC? To precisely specify which IP packets are mapped to each LSP Done by providing a FEC specification for each LSP

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LSP - FEC MappingFEC specified as a set of two elements

(currently) 1. IP Address Prefix - any length from 0 - 32 2. Host Address - 32 bit IP address A given packet matches a particular LSP if and only if IP Address Prefix FEC element matches packets IP destination address

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Rules for Mapping packet to a LSPIf exactly one LSPs Host Address FEC element ~

packets IP destination address, packet is mapped to that LSP If there are multiple LSPs satisfying the above condition, then the packet is mapped to one of those LSPs If a packet matches exactly one LSP, packet is mapped to that LSP If packet matches multiple LSPs, mapped to one with the longest prefix match

W LSP to be chosen - outside the scope of this presentation hich

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Label SpacesUseful for assignment and distribution of

labels Two types of label spacesPer interface label space: Interface-

specific labels used for interfaces that use interface resources for labels Per platform label space: Platform-wide incoming labels used for interfaces that can share the same label space

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A six octet quantity used to identify specific label space within an

LDP Identifiers

LSR First four octets encode LSRs IP address Last two octets identify specific label space Representation : e.g., 171.32.27.28:0, 192.0.3.5:2

Last two octets for platform-wide label spaces

are always both zero

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A mechanism that enables an LSR to discover

LDP Discovery

potential LDP peers Avoids unnecessary explicit configuration of LSR label switching peers Two variants of the discovery mechanismbasic discovery mechanism: used to discover LSR

neighbors that are directly connected at the link level extended discovery mechanism: used to locate LSRs that are not directly connected at the link level

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Basic discovery mechanism To engage - send LDP Hellos periodically LDP Hellos sent as UDP packets for all routers on that subnet Extended discovery mechanism To engage - send LDP targeted Hellos periodically Targeted Hellos are sent to a specific address Targeted LSR decides whether to respond or to ignore th targeted Hello LDP Link Hello sent by an LSR carries the LDP identifier for the label space the LSR intends to use for the interface

LDP Discovery contd..

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Exchange of LDP discovery Hellos triggers session

Session establishment

establishment Two step process

Transport connection establishment If LSR1 does not already have a LDP session for the exchange of label spaces LSR1:a and LSR2:b, it attempts to open a TCP connection with LSR2 LSR1 determines the transport addresses at its end (A1) and LSR2s end (A2) of the TCP connection If A1>A2, LSR1 plays the active role; otherwise it is passive Session initialization Negotiate session parameters by exchanging LDP initialization messages

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Session Initialization State Transition NON Diagram EXISTENTRx Any other msg or Timeout Tx NAK msg Session connection established Rx Any LDP msg except Init msg or Timeout (Active Role) Tx Init msg (Passive Role) Rx Acceptable Init msg/ Tx Init msg & KeepAlive msg INITIALIZED

OPENREC Rx KeepAlive msg

OPENSENT

Rx Acceptable Init msg Tx KeepAlive msg OPERATION AL All other LDP msgs

Rx Any other msg or Timeout Tx NAK msg

Rx - Receive Tx - Transmit

Rx Shutdown msg or Timeout Tx Shutdown msg

Session Initialization State Transition TableSTATE NON EXISTENT INITIALIZED EVENT NEW STATE Session TCP connection established INITIALIZED Transmit initialization message (Active Role) Receive acceptable initialization message (Passive role) Action: Transmit initialization message and Keep alive message Receive Any other LDPmsg Action: Transmit error notification msg (NAK) and close transport connection OPENSENT OPENREC

NON EXISTENT

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Session Initialization State Transition Table cont.) STATE EVENT NEW STATEOPENREC Receive KeepAlive msg OPERATIONAL NON EXISTENT Receive Any other LDP msg Action: Transmit Error Notification msg (NAK) and close transport connection Receive acceptable Init msg Action: Transmit KeepAlive msg Receive Any other LDP msg Action: Transmit Error msg (NAK) and close transport connection OPERATIONAL Receive Shutdown msg Action: Transmit Shutdown and close transport connection All other LDP messages NON EXISTENT msg OPERATIONAL

OPENSENT

OPENREC NON EXISTENT

Label Distribution and ManagementTwo label distribution techniques Downstream on demand label distribution: An LSR can distribute a FEC label binding in response to an explicit request Downstream Unsolicited label distribution: Allows an LSR to distribute label bindings to LSRs that have not explicitly requested them Both can be used in the same network at the

same time; however, each LSR must be aware of the distribution method used by its peer

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Label Distribution Control Mode

Independent Label Distribution Control Each LSR may advertise label mappings to its neighbors at any time In independent Downstream on Demand mode - LSR answers without waiting for a label mapping from next hop In independent Downstream Unsolicited mode - LSR advertises label mapping for a FEC whenever it is prepared Consequence: upstream label can be advertised before a downstream label is received

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Label Distribution Control Mode contd..Ordered Label Distribution Control Initiates transmission of label mapping for a FEC only if it has next FEC next hop or is the egress If not, the LSR waits till it gets a label from downstream LSR LSR acts as an egress for a particular FEC, ifnext hop router for FEC is outside of label switching network FEC elements are reachable by crossing a domain boundary31

Label Retention ModeConservative Label Retention Mode Advertised label mappings are retained only if they are used for forwarding packets Downstream on Demand Mode typically used with Conservative Label Retention Mode Advantage: only labels required are maintained Disadvantage: a change in routing causes delay Liberal Retention Mode All label mappings are retained regardless of whether LSR is next hop or not reaction to routing changes will be quick

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Label Information BaseLSR maintains learned labels in Label

Information Base (LIB) Each entry of LIB associates an FEC with an (LDP Identifier, label) pair When next hop changes for a FEC, LSR will retrieve the label for the new next hop from the LIB

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H i ra rch i lO p e ra ti n i e ca o n M P LSExample: External Routers A,B,C,D,E,F - Talk BGP Internal Routers 1,2,3,4,5,6 - Talk OSPF C1 Domain #2 2 3 4 5 6

D F

A

B

E

Domain #1

Domain #334

Note: Internal routers in domains 1 and 3 not shown

Hierarchical Operation contd..When IP packet traverses domain #2, it will contain

two labels, encoded as a label stack Higher level label used between routers C and D, which is encapsulated inside a lower level label used within Domain #2 Operation at CC needs to swap BGP label to put label that D

expects C also needs to add an OSPF label that 1 expects C therefore pushes down the BGP label and adds a lower level label

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Label StackMultiple labels are carried in data packets e.g. data packet carried across Domain #2 Concept of stacking provides a mechanism to segregate streams within a switched path one useful application of this technique is in Virtual Private Networks Advantage of Hierarchical MPLS is that the

internal routers need not know about higher level (BGP) routing

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MultipathMany IP routing protocols support the notion of

equal-cost multipath routes Few possible approaches for handling multipath within MPLS First approach:

separate switched path from each ingress

node to the merge point preserves switching performance, but at the cost of proliferating the number of switched paths

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Second approach Only one switched path from one ingress node to a destination Conserves switched paths but cannot balance loads across downstream links as well as other approaches LSP may be different from the normal L3 path Third approach: Allows single stream to be split into multiple streams, by using L3 forwarding e.g. might use a hash function on source and destination IP addresses Conserves paths at the cost of switching performance

Multipath contd..

Explicit Routing in MPLSTwo options for route selection: Hop by hop routing Explicit routing Explicit Routing (aka Source Routing) is a

very powerful technique

With pure datagram routing overhead of

carrying complete explicit route is prohibitive MPLS allows explicit route to be carried only at the time the LSP is setup, and not with each packet MPLS makes explicit routing practical

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Explicit Routing in MPLS contd..In an explicitly routed LSP the LSP next hop is not chosen by the local node selected by a single node, usually the ingress The sequence of LSRs may be chosen by configuration (e.g., by an operator or by a centralized server) an algorithm (e.g., the ingress node may make use of topological information learned from a link state routing protocol)40

Loops and Loop HandlingRouting protocols used in conjunction with

MPLS are based on distributed computation which may contain loops Loops handling - 3 categoriesLoop Survival Loop Detection Loop Prevention

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Loop SurvivalMinimizes the impact of loops by limiting the

amount of resources consumed by the loop Methodbased on use of TTL field which is

decrement at each hop Use of dynamic routing protocol converging rapidly to non-looping paths Use of fair queuing

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Loop DetectionLoops may be setup but they are subsequently

detected The detected loop is then broken by dropping label relationship Broken loops now necessitates packets to be forwarded using L3 forwarding

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Loop Detection (cont.)Method is based on transmitting a Loop

Detection Control Packet (LDCP) whenever a route changes LDCP is forwarded towards the destination untillast MPLS node along the path is reached TTL of the LDCP expires it returns to the node which originated it

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Loop PreventionEnsures that loops are never set up labels are not used until it is sure to be loop

free Methodslabels are propagated starting at the egress

switch use source routing to set up label bindings from the egress switch to each ingress switch

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Leaf

Leaf

Leaf

Detects loop immediately

LSR Ingress Node Egress Node

Link removed from tree

Change in Link

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Traffic Engineering and Performance ObjectivesTraffic Engineering (TE) is concerned with

performance optimization of operational networks The key performance objectivestraffic oriented - aspects that enhance the

QoS of traffic streams e.g minimization of packet loss resource oriented - aspects that pertain to the optimization of resource utilization e.g efficient management of bandwidth

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Performance Objectives (cont.)Minimizing congestion is a major traffic and

resource oriented performance objective Congestion manifest under two scenariosnetwork resources are insufficient or

inadequate

can be solved by capacity expansion or classical congestion control techniques

traffic streams are inefficiently mapped

onto available resources

can be reduced by adopting load balancing policies

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Traffic and Resource ControlThe traffic engineer acts as the controller in

an adaptive feedback control system which includesa set of interconnected network elements a network performance monitoring system

& network configuration management tools

The traffic engineer formulates control

policies, observes the state of the network, characterizes the traffic and applies the control actions in accordance to the control policy49

MPLS and Traffic EngineeringMain components used Traffic Trunk - aggregation of traffic flows of the same class which are placed inside a Label Switched Path Induced MPLS Graphanalogous to a virtual topology in an overlay model logically mapped onto the physical network through the selections o LSPs for traffic trunk comprises a set of LSRs which act as nodes of the graph and a set of LSPs which provide logical point to point connectivity between LSRs and thus act as edges of the graph50

Augmented CapabilitiesSet of attributes associated with traffic

trunks which collectively specify their behavioral characteristics Set of attributes associated with resources which constrain the placement of traffic trunks through them A constraint based routing framework which is used to select paths for traffic trunks subject to constraints imposed

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Basic operation on traffic trunksEstablish - create an instance of a traffic trunk Activate - cause to start passing traffic Deactivate - stop passing traffic Modify Attributes Reroute - administratively or by underlying

protocols Destroy - reclaim all resources such as label space and bandwidth

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Basic attributes of traffic trunkTraffic parameter attribute - capture the

characteristics of the traffic streams Generic Path selection and maintenance attributes - defines rules for selecting route taken by traffic trunk and rules of maintaining the paths Priority attribute Preemption attribute Resilience attribute Policing attribute

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Resource AttributesPart of the topology state parameters used to

constrain the routing of traffic trunks through specific resources Main componentsMaximum Allocation Multiplier (MAM) -

administratively configured to determine the proportion of resource available for allocation Resource Class Attribute - administratively assigned parameters which express some notion of Class for resources

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Enables a demand driven, resource reservation

Constraint Based Routing

aware, routing paradigm to co-exist with current topology driven protocols uses the following inputstraffic trunk attributes resource attributes other topology state information

Basic features prune the resources that do not meet the requirements of the traffic trunk attribute run a shortest path algorithm on the residual graph55

Constraint Based Routing (cont.)Strict & Loose Explicit Routes Constraint Based LSP (CRLSP) is calculated at one point at the edge of the network based on certain criteria special char. such as assigning certain bandwidth can be supported The route is encoded as a series of Explicit routed hops contained in a CR based route TLV

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Constraint Based Routing (cont.)

Traffic Characteristics Described in the Traffic Parameter TLV in terms of peak rate, committed rate and service granularity Preemption Setup and Holding priorities are used to rank new and existing paths respectively to determine if new paths can preempt existing paths Allocation of these priorities is a network policy57

Constraint Based Routing (cont.)Route Pinning applicable to segments of an LSP that are loosely routed i.e the next hop is an abstract node used if the LSP need not be changed Resource Class While setup , indication must be given as to which class the CRLSP can draw resources from

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I p l m e n ta ti n m e o C o n si e ra ti n d oManagement InterfaceConventiona l IGP Process Link State Database59

MPLS

Constraint Based Routing Process

Resource Attribute Availability Database

Quality of Service using CRLSPDelay Sensitive Service the network commits to deliver with high probability, user datagrams at a rate of PDR with minimum delay and delay requirements Datagrams in excess of PDR will be discarded Throughput Sensitive Service the network commits to deliver at a rate of at least CDR Datagrams with higher CDR have lower probability of being delivered Best Effort Service No expected service is guaranteed60

Ta g S w i i g tch nTerminologies Tags Tag Switching Router (TSR) Tag Edge Router (TER) Analogies in Label Switching Labels Label Switching Router

Edge Label Switching Router Tag Forwarding Information Label Switching Forwarding Base (TFIB) Table Tag Distribution Protocol Label Distribution Protocol (TDP)61

Destination Based RoutingA TSR participates in unicast routing protocols

to construct its mapping between FECs and next hops This mapping is used by the Tag Switching Control component for constructing the TFIB which is used for actual packet forwarding

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fo rw a rd i g m o d e lo f Ta g n Sw i i g tch nA if0 if2 if1 if1 if2 if0 if2 B if1 E if0192.16/16

if0

C

if2

if1

D

if0

TSR63

Information for constructing TFIBA local binding between the FEC and a tag takes a tag from the pool of free tags and uses it as an index in the TFIB to set the incoming tag entry A mapping between the FEC and the next

hop for that FEC (provided by the routing protocol(s) running on the TSR) A remote binding between the FEC and a tag that is received from the next hop

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I i a lT FI E n tri s n ti B eIncoming Outgoing tag tag On TSR A On TSR B On TSR C On TSR D On TSR E 100 6 17 5 6 ? ? ? ? ? Next hop TSR B TSR E TSR D TSR E TSR E Outgoing Interface If1 If1 If2 If0 If065

T FI E n tri s a fte r Ta g B e D i b u ti n stri oIncoming Outgoing tag tag On TSR A On TSR B On TSR C On TSR D On TSR E 100 6 17 5 6 6 6 5 6 ? Next hop TSR B TSR E TSR D TSR E TSR E Outgoing Interface If1 If1 If2 If0 If066

B e h a vi r d u ri g ro u ti g o n n ch a n g eA if0 if2 if1 if1 if2 if0 if2 Link Down if0 C if2 if1 D if0 TSR67

B if1 E if0

U p d a te d T FI BIncoming Outgoing tag tag On TSR A On TSR B On TSR C On TSR D On TSR E 100 6 17 5 6 6 6 5 6 ? Next hop TSR B TSR E TSR D TSR B TSR E Outgoing Interface If1 If1 If2 If0 If068

Hierarchy of Routing KnowledgeAll TSRs within a routing domain participate

in a common intra-domain routing protocol and construct TFIB corresponding to destinations within the domain All border TSRs or TERs within a domain and directly connected TERs from other domains also exchange Tag binding information via inter-domain routing protocol

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Hierarchy of Routing Knowledge (cont.)To support forwarding in the presence of

hierarchy of routing knowledge, Tag switching allows a packet to carry several tags organized as a tag stack At the ingress a tag is pushed onto the tag stack, and at the egress a tag is popped off a the stack

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H i ra rch y o f R o u ti g e n kn o w l d g e m o d e l eRouting domain B Routing domain A Routing domain C

V

T

X

Y

W TSR

Z

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T FI E n tri s i R o u ti g B e n n D om ai A nIncoming Outgoing tag tag On TSR A On TSR B On TSR C On TSR D N/A 10 12 17 10 12 17 N/A Next hop TSR X TSR Y TSR W TSR W

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La b e lS ta ck D u ri g n H i ra rch i lR o u ti g e ca nTSR Z distributes label 2 to TSR W and TSR W gives label 5 to TSR T for the purpose of inter-domain routingTop of Stack

10 2 2

Top of Stack

Stack after processing in TSR T

Stack after processing in TSR W73

Multicast in Tag SwitchingSelects the distribution tree based only on tag carried in a packet interface on which the packet arrives TSR maintains its TFIB on a per interface basis TSRs connected to a common sub-network

agree among themselves on a common tag associated with a particular multicast tree

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Multicast in Tag Switching (cont.)Procedures are used to partition the set of

tags for use with multicast into disjoint subsets and care is taken to avoid overlapping with the help of HELLO packets TSR connected to a common sub-network and those which are a part of the same distribution tree elect one TSR that will create the tag bindings and distribute them and any TSR can join the group using the JOIN command

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M u l ca st m o d e li Ta g ti n Sw i i g tch nA if0 if0 D if1 B TSR

if2 if0 if0

E

F

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RSVP with Tag Switching

RSVP is supported by the help of a RSVP

object - the tag Object The tag object binding information for an RSVP flow is carried in the RSVP RESV message The RESV message carries the tag object containing the tag given by a TSR and also information about the local resources to be used The reservation state is refreshed once the flow is set up using the RESV message

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Explicit RoutesTag switching supports explicit routes with the

help of a RSVP object - the Explicit Route Object The object is carried in the RSVP PATH message The tag information is carried in the Tag Object by the RSVP RESV

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IP SwitchingIntroduced by Ipsilon Already been tested in the field Significant Innovation: Defined a switch

management protocol (GSMP) along with label binding protocol called Ipsilon Flow Management Protocol (IFMP) General Switch Management Protocol (GSMP) - allows an ATM switch to be controlled by an IP switch controller

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IP Switching OverviewIP over ATM models are complex and

inefficient - involve running two control planesATM Forum signaling and routing IP routing and address resolution on top

In contrast IP Switching uses IP component plus label binding protocol completely removes ATM control plane Goal: To integrate ATM switches and IP

routing in a simple and efficient way

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Removing ATM Control PlaneATM ARP IP MARS PNNI Q.2931 ATM hardware (a) NHRP IP IFMP

ATM hardware (b)

(a) (b)

IP over Standard ATM IP Switching81

IP Switching Architecture

Switch controller control processor of the system uses GSMP to communicate with ATM switch itself runs IP routing and forwarding code Default VC defined to get control traffic before IP Switching is performed uses well known VCI/VPI value also used for data that doesnt yet have a label

IP Switch ArchitectureSwitch controllerFlow Classification and control

Default VC Data VC

GSMP IFMP

To upstream switch

Routing and forwardin g

To downstream switch

GSMPDefault VC

Switch

Data VC83

IP Switching relies on IP protocols to establish routing information to determine next hop Flow classification and control module selects flows

IP Switching Basics

from incoming traffic IP flow refers to a sequence of datagrams

from one source to one destination, identified by the

ordered pair can also refer to a flow at finer granularity, e.g., different applications between same pair of machines, identified by < source address, source port, destination address, destination port>

Flow RedirectionRedirection: Process of binding labels to flows and

establishing label switched paths Example:

data is flowing from A via B to C on default VC B sends a redirect to A specifying flow y and the

label (VPI/VCI) on which it expects to receive If C issues a redirect to B for flow y, B forwards y on the VPI/VCI specified by C Since same flow y enters B on one VC and leaves on another, B uses GSMP to inform its switching element to set up the appropriate switching path

Flow RedirectionRedirect: Flow y VPI/VCI 3/57

ADefault VC 3/57

BDefault VC

C

Switch Controller Switch Element

Switch B issues a REDIRECT message to switch A Redirect: Flow y VPI/VCI 3/57 Redirect: Flow y VPI/VCI 2/22

ADefault VC

BDefault VC

C

Switch Controller Switch Element

3/57 2/22 Switch B and C redirect the same flow, allowing it to be switched at B

Ipsilon Flow Management Protocol (IFMP)Designed to communicate flow to label

binding information IFMP is a soft state protocol IFMPs Adjacency Protocol:

Used to communicate and discover

information about neighbors Adjacency message sent as limited broadcast

IFMPs Redirection Protocol used to send appropriate messages for flow-label bindings

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IFMPs Redirection ProtocolDifferent message types defined: REDIRECT: used to bind label to a flow RECLAIM: enables label to be unbound for subsequent re-use RECLAIM ACK: Acknowledgement for RECLAIM message ERROR: Used to deal with various error conditions Common header format

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FMP Redirect Protocol Message m Format Vr i n e so O cd p oe Ce ku hc sS n e I sa c e dr nt ne Pe I sa c e r nt ne Sq e c Nme e une u br M s g b d :v ra l l n t e a e o y a i be e gh s

IFMP REDIRECT message bodyF wy e lo t p F wD nt lo I le gh L bl ae F w e t ie lo id nif r L e im if t e

Encapsulation of Redirected FlowsLLC SN AP IP header Data AAL5 trailer

Encapsulation of IP packet on the default VC

IFMP flow type header

Data

AAL5 trailer

Encapsulation of IP packet on the redirected VCs

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Management Protocol (GSMP)GSMP is a master/slave protocol ATM switch is the slave Master could be any general purpose computer The protocol allows the master to Establish and release VC connections across the switch Perform port management (Up, Down, Reset, Loopback) Request Data (configuration information, statistics) Allows slave to inform master if something interesting, such as link failure, happens on the 91 switch

GSMP packets are LLC/SNAP encapsulated

GSMP contd..

and sent over ATM link using AAL5 GSMP Adjacency Protocolat the other end of the link and to monitor link status

used to gain information about the system

GSMP Connection Management Protocol used to ensure consistency between the GSMP master and slave also specifies the QoS using a priority field

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Implementations & Contributions IP Switching products

available since 1996 Ipsilon product family uses Intel Pentium-based PC as

the switch controller Also offers a number of ATM switches that are controlled by the switch controller

IP Switching made the following significant

contributions to label switching effort:

first to deliver real products and caused activity that

resulted in the development of Tag Switching and ultimately the formation of MPLS working group contributed GSMP

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