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Lecture 4. MPLS traffic engineering

Lecture 4. MPLS traffic engineering. D. Moltchanov , TUT, Spring 2010. Outline. Creating LSPs CR-LDP RSVP-TE. Creating LSPs. Creating LSP: protocols. Label distribution for each node {incoming if-ce , label} - {outgoing if-ce , label} Label distribution sets up LSPs!

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Lecture 4. MPLS traffic engineering

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  1. Lecture 4. MPLS traffic engineering D. Moltchanov, TUT, Spring 2010

  2. Outline • Creating LSPs • CR-LDP • RSVP-TE

  3. Creating LSPs

  4. CreatingLSP: protocols • Label distribution for each node • {incoming if-ce, label} - {outgoingif-ce, label} • Label distribution sets up LSPs! • There are a number of protocols • For better development • LSPcan be set up • Upon request from ingress node • Upon request from interior or egress node • Joint request from transit/ingress/egress node • Label are distributed towards source (ingress node) • Creating LSPs • LDP • CR-LDP • RSVP

  5. CreatingLSP: LDP, CR-LDP,RSVP • LDP, Label Distribution Protocol • Based solely on IGPs(so that SPF in nature) • No source routing: mapping of IGP info to switching tables • Exchange of labels between adjacent nodes • CR-LDP, Constrained Routing Label Distribution Protocol • LDP + source routing • Extension to support traffic engineering • Request: ingress to egress, mapping: egress to ingress • RSVP, Resource ReserVation Protocol • RSVP extended to support traffic engineering • Source routing • Bandwidth reservation • Request: ingress to egress, mapping: egress to ingress • Traffic engineering MPLS = source routing

  6. MPLS:IPtopology

  7. MPLS:IProuting

  8. MPLS:LDP

  9. MPLS:LDP

  10. MPLS:what we may want • Load balancing? Explicitly-routed LSP (ER-LSP)

  11. CR-LDP

  12. 2. To next LSR. Path:C,D 3. Last point 1. Message‘Label Request’. Explicit path: B,C,D 6. When message is received, path is established 5. LSR C gets label for LER D. 4. Label binding message. CR-LDP: signaling Egress node Ingress node ER-LSP LER A LSR B LSR C LER D

  13. CR-LDP: what it does? • Establishes explicitly routed LSP • Uses CSPF for that • Signals traffic requirements to routers • Routers reserve bandwidth on a path • Provides priorities between LSPs • Preemption is allowed • Additional features • Path restoration • Path protection

  14. CR-LDP: constrained SPF (CSPF)

  15. & & = CR-LDP: choosingER-LSP • CR-LDP Constraint Routing LDP • For example, use nodes/links with • Enough resources • The same color • Propagation delay is less than X

  16. CR-LDP:traffic parameters • Frequency:how many packets can be in buffer • Relative weight of LSP • EBS, CDR, CBS

  17. CR-LDP:negotiation flags • If a parameter is set, negotiation is allowed • Can be changes by any node to lower value • F1:PDR • F2: PBS • F3: CDR • F4: CBS • F5: EBS • F6: relative weight Res F6 F5 F4 F3 F2 F1 Label request:negotiation allowed Label bindings:negotiation is not allowed

  18. CR-LDP:priorities • EachCR-LSP requestcarriesLSP priority • How to distributed resources • Important when nodes/links fail • setupPriority and holdingPriority • 8 levels for each • WhenLSP is setting up • setupPriority is compared toholdingPriority • LSPwith lower priority can be interrupted • Process my continue • New connection request for intercepted LSP • Up to LSP with least priority

  19. RSVP-TE

  20. 3. RESVmessage. Label + traffic parameters. 2. MessagePATH to the next hop MessagePATH. ERpath: B,C,D 4. Reservarion state RESV. MessageRESVto the next hop PATHRESV exchange 5. Upon reception ofRESV,ERis set up. PATH и RESV PATH и RESV RSVP-TE: signaling LER A LSR B LSR C LER D

  21. NodeA NodeB NodeA NodeB REQUEST MAPPING RESV PATH PATH PATH RESV PATH RESV RESV RESV PATH RSVP-TE: RSVP vs. CR-LDP RSVP LDP/CR-LDP That is all!! Forever!! Time

  22. RSVP-TE: PATHandRESV • Message PATH: source -> receiver • Contain router notification option • Sets up soft state in a router • Does not reserve resources, just notifies about possible LSP! • Message RESV: receiver -> source • Take exactly the same path in a network • Finalize all states in routers • Reserve resources

  23. RSVP-TE: errors • RSVPdefines error messages • Transit nodes may notify end nodes • Two error messages • PATHERRis sent to ingress node • RESVERRis sent to egress node • Sometimes errors are undetected e.g. node fails • States are not cleared • Ingress/egress nodes may initiate tearing down of LSP • LSP is cleared after several PATH/RESV exchange failures

  24. RSVP-TE: RSVPPATH • RSVP PATH • To describe LSP and resource requirements • RSVP PATH contains • Session ID: egress node address, Tunnel IDforLSP • RSVP-Hop: interface address of previous hop inLSP • Sender-Template: ingress node address, unigue LSP ID • Sender-Tspec: traffic parameters • Session-Atribute: LSP priority andLSP name • Explicit Route Object (ERO): intended path in the network • Can be set manually • Can be set automatically by CSPF algorithm • Record Route:actual path in the network • Used for loop detection

  25. RSVP-TE: RSVP RESV • RSVP RESV • To reserve resources and set up LSP • RSVP RESV contains • Session ID: egress node address, Tunnel ID forLSP • RSVP-Hop: interface address of previous hop inLSP • Style:type of recourse allocation • Fixed filter • Explicit shared filter • FlowSpec:contains a copy ofTspec • Filter-Spec: ingress node address, uniqueLSP ID • Label:label value for binding • RecordRoute: actual path in a network • Used for loop detection

  26. RSVP-TE: RSVP explicit route object • LSP can request bandwidth reservation • Default:at each interface up to 100% can be reserved • Can be manually changed • Explicit Route Object (ERO) • This is load balancing related function • Allows ingress node to request a certain route in a network • Two mechanisms • LOOSE NODE: node that have to be in the path • SPFup to first such node • SPF between such nodes • SPFfrom the last such node to egress node • STRICT NODE: • Two nodes must be directly connected

  27. RSVP-TE: using RSVP ERO • ERO • D: STRICT • Only if the next node is the D • If not, PATHERR is returned • B: LOOSE • After that routing tables are used

  28. RSVP-TE: setting ERO manually • Requires knowledge of the network topology • There could be mistakes • Example: loop detection algorithm may lead to errors • Network topology with IGP metrics • BandE:LOOSE • EsendsRSVP PATHback toB (according to its routing table) • Bdetects loopand returns PATHERR to ingress node

  29. RSVP-TE: setting ERO automatically • EROcan be set automatically • All the nodes are STRICT • Automatic ERO is the result of TED analysis • TED: Traffic Engineering Database • Based onIGP with traffic engineering support (IGP-TE, IGP-QoS) • IS-ISandOSPFhave been extended to support TE • IS-IS-TEandOSPF-TEdistributed info forTED • Own interface and neighbor's interface • Maximum resolvable bandwidth • Current value of reserved bandwidth • Traffic engineering metrics • Administrative group • Ingress node useCSPFinTED to determine explicit route

  30. RSVP-TE: constrained SPF (CSPF)

  31. RSVP-TE: setting ERO automatically • CSPF algorithm • Detect a set of paths that satisfy some constraints • CSPFalgorithms • Neglects links that do not have enough bandwidth • Neglects links that do not have a certain color • Neglects links that have a certain color • Determines shortest path • If there are still a number of shortest paths • Path with the least number of physical nodes • Is still there a number of paths • Random is chosen or • Most filled is chosen or • Least filled is chosen • Result -> ERO with STRICT nodes only • RSVP-TE sends RSVP PATH with this ERO for label bindings

  32. RSVP-TE: administrative groups • Each interface is assigned to a administrative group • To distinguish between them we can use • Color: gold, silver, bronze • Some titles: voice, control, best-effort • Group information is distributed by IGP • 32 bits vector • CSPFcan be configured such that • A certain group(s) is included • A certain group(s) is excluded • LogicalANDon inclusionandexclusion of groups

  33. RSVP-TE: administrative groups • LSPis configured for inclusion of groups • LSP fromCtoEmust include‘Gold’and‘Silver’ • AllIGPmetric are 1

  34. RSVP-TE: administrative groups • Neglect links that do not contain“Gold”, “Silver” • SPFin what is left • EROis created

  35. RSVP-TE: administrative groups • LSPshould be such that some group is excluded • LSP fromCtoEmust excludeBest Effort • AllIGPmetrics are 1

  36. RSVP-TE: administrative groups • Neglect links containingBest Effort • SPFover what is left • EROis created

  37. RSVP-TE: administrative groups • Simultaneous inclusion and exclusion of groups • LSP fromCtoE: • Exclude“Best Effort” and “Management” • Include“Gold”or”Silver”

  38. RSVP-TE: administrative groups • Neglect links not having “Gold” or“Silver” • Neglect linkshaving “Best Effort” and “Management” • SPFover what is left

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