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Multicasting In MPLS Network

Multicasting In MPLS Network. Christy Gnanapragasam christy@sce.carleton.ca. Nov 08, 2003. Introduction and Background Literature survey IP Multicasting Multicasting in MPLS Difficulties in supporting A New approach (ERM2) Extension to ERM2 (ERM2-Ext) (Own work) Performance analysis

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Multicasting In MPLS Network

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  1. Multicasting In MPLS Network Christy Gnanapragasam christy@sce.carleton.ca Nov 08, 2003

  2. Introduction and Background Literature survey IP Multicasting Multicasting in MPLS Difficulties in supporting A New approach (ERM2) Extension to ERM2 (ERM2-Ext) (Own work) Performance analysis Summary Outline AONL & EION

  3. Introduction and Background AONL & EION

  4. Advantages of multicasting Reduction in network resource consumption Source Link stress Example applications: Audio/video distribution Push applications Audio/video conferencing Requirements of this applications (QoS): Bandwidth, bounded delay and low loss rate Introduction AONL & EION

  5. There is no standardized algorithms for multicasting in MPLS However, the power of MPLS can provide QoS for IP multicast in MPLS. Problem arise, when mapping L3 multicast trees in to L2 LSPs. Flood and prune Source/shared trees Uni/bi directional trees Encapsulated multicast Difficulties in supporting IP multicast in MPLS AONL & EION

  6. ERM: Easy to implement and it requires simple modification to current IP mulicasting protocols But, LSRs need to participate in routing process ERM2: In MPLS-TE, Until a PLR has a backup path available, the PLR must clear relevant four flags in the corresponding RRO sub-object Local Protection available flag PLR should set this when a backup path is available. If no established backup path or it is in DOWN state, PLR should clear this flag and should send a updated RESV message Local Protection in use flag PLR Should set this flag if it redirecting traffic into the backup path else should be clear Node Protection flag PLR should set this flag if backup path is protected against the failure of immediate downstream node. BW Protection flag PLR should set this flag if the backup path offers a BW guarantee. ERM2 AONL & EION

  7. Difficulties: LSP Design Multicast tree requires point-to-multipoint LSP setup, but only point-to-point LSP setup is supported by MPLS. Volatile LSPs Dynamic behavior of group members Singling overhead and over consumed labels Traffic aggregation: Unicast traffics are normally aggregated if ingress and egress LERs are same for scalability. Not possible in multicast traffic. Coexistence of Layer 2 and Layer 3 forwarding in LSRs. Two cases: Switched over from shared tree to source based tree Same label for unicast and multicast traffic AONL & EION

  8. Solution to mentioned problems • Edge Router Multicasting • In this approach, trees are formed by branching at Edge router. AONL & EION

  9. ERM converts the multicast flow into multiple unicast flow Simplifies the LSP setup: Diverging nodes are only LERs No need for point-to-multipoint LSPs. Makes multicast flow aggregatable: Unicast and multicast traffic can be treaded in a same way and scalability will not be compromised Relaxes the requirements at Core Routers: No modification needed at LSRs Advantages of ERM AONL & EION

  10. ERM concept can be used to build trees in MPLS by slightly modify existing IP multicast routing protocols. PIM_SM and CBT uses Rendezvous Point and explicit Join messages But need some modifications needed Select LER as RP of the tree Allow a sub tree to join at only LER ERM in depth AONL & EION

  11. We can add two more techniques that can optimize the end results. Where to join if there are multiple choices. Dynamic tree optimization Advantages. Minimize the End-to-End delay Minimize the bandwidth consumption Minimize the packet processing (L2->L3->L2) Modification to ERM2 (own work) AONL & EION

  12. ADD SUBTRACT QUARY JOIN PRUNE R2 RESULT R1 • ERM2 illustrations LER1 LER6 S LER2 MM LER3 LER5 LER4 AONL & EION

  13. S QUARY R2 RESULT • ERM2-Ext Joining choice R1 LER1 LER6 LER2 MM LER3 LER5 LER4 AONL & EION

  14. R2 • ERM2-Ext: Dynamic tree optimization R1 1) Unwanted packet processing (L2->L3->L2) 2) ETE hop delay is larger than it should be (5->4) LER1 LER6 S LER2 MM 3) Extra bandwidth wastage (5 link ->4link) LER3 LER5 LER4 AONL & EION

  15. Challenges: Triggering the optimization algorithm Optimization can be triggered when a LER does not have any directly connected receivers and it has one or more downstream peer LERs. Optimization Which nodes should be refreshed (rearranged) Where should they join (who is the parent) Which order those nodes should be rearranged Introducing a simple algorithm would optimize the tree and the performance AONL & EION

  16. RefreshTrigger (list of children) Refresh (potential candidates) Snapshot of a tree Where should they join: Easy solution: join them in parent node of the leaving LER All of these nodes are LERs and they all have directly attached Receivers 5 5 MM Which nodes need to be refreshed: children 3 6 5 4 R 3 2 3 5 4 5 3 • Which children to refresh first • Find the potential candidates (LERs) AONL & EION

  17. Find a order: which children need to be refreshed first to obtain optimal result. Chose the one has less cost to source (root) This new child also be part of the potential candidate for next child. Finding the potential candidates Which is a sub-set of on-tree LERs Sub-tree should exclude Leaving LER Children of leaving LER What about descendant of leaving node Should be excluded Why? MM responsibilities: AONL & EION

  18. Find the potential candidates for joining the tree 5 5 MM 3 6 5 4 R 3 2 3 5 4 5 3 MM does not know the relationship between nodes, it just know the distance from source To exclude descendants, may be we can use the height for now AONL & EION

  19. Bandwidth consumption AONL & EION

  20. End to End Delay AONL & EION

  21. ERM2 is a simple algorithm that supports the multicasting in MPLS. It excludes the need for point-to-multipoint LSP setup It excludes the participation of LSR in tree or tree building ERM2-Ext: for more optimization Choice of parent when multiple joining points are possible Dynamically refreshing the tree Two new messages RefeshTriggring and Refresh Advantages Minimize the bandwidth consumption Minimize the end to end delay Minimize the processing overhead (L2->L3->L2) Summary AONL & EION

  22. [1] Boudani, A and Cousin, B.;”A New Approach to Construct Multicast Trees in MPLS Network,” Computers and Communications, 2002. Proceedings. ISCC 2002. Seventh International Symposium on, 1-4 July 2002 Pages: 913 – 919. Baijian Yang and Mohapatra, P.” Edge router multicasting with MPLS traffic engineering,” Networks, 2002. ICON 2002. 10th IEEE International Conference on, 27-30 Aug. 2002 Pages: 43 – 48 Young-Kyu Oh, Dong-Keun Kim, Hun-Je Yoen, Mi-sun Do and Jaiyong Lee,” Scalable MPLS multicast using label aggregation in Internet broadcasting systems,” Telecommunications, 2003. ICT 2003. 10th International Conference on, Volume: 1, 23 Feb.-1 March 2003.Pages:273 - 280 Vol.1 Zhongshan Zhang, Keping Long, Wendong Wang, Shiduan Cheng, “The new mechanism for MPLS supporting IP multicast,”, Circuits and Systems, 2000. IEEE APCCAS 2000. The 2000 IEEE Asia-Pacific Conference on, 4-6 Dec. 2000 Pages: 247 – 250 M. Ramalho. Intra- and Inter-domain multicast routing protocols: A survey and taxonomy. IEEE Communications Survey sand Tutorials, 3(1):2–25, first Quarter 2000 Almeroth, K.C., “The evolution of multicast: from the MBone to interdomain multicast to Internet2 deployment,“ Network, IEEE , Volume: 14 , Issue: 1 , Jan.-Feb. 2000, Pages:10 – 20 References AONL & EION

  23. Thank You

  24. Explicit multicast [Boivie & al.] Xcast packet explicit list of group members list of unicast addresses in Xcast packet header No multicast routing table standard unicast routing protocol no additionnal entry No management protocol Xcast solution AONL & EION

  25. uses LSPs between branching nodes no multicast states into no-branching nodes enhances scalability of MPLS domain for multicast trafic MPLS Multicast Tree AONL & EION

  26. Multicast trees have: few branching nodes many non-branching nodes A branching node a router with distinct nexthops for a multicast tree Branching nodes from REUNITE study from our study AONL & EION

  27. Membership management delegated to another protocol multicast source knows somehow the IP address of every member of the multicast group When size of multicast group increases size of destinations list increases packet processing time increases packet length increases Xcast problems AONL & EION

  28. Multicasting in MPLS In designing a MPLS multicast protocol, we must deal with two problems. • Creating multicast tree. • Allocating and distributing labels. Definitely, LDP must deal with the second problem. However, creating Multicast tree can be based on: • Topology driven: Map the L3 tree in the routing protocol into L2. • Request driven: By signaling • Traffic driven: Map the L3 tree in the routing protocol into L2 when data arrive. AONL & EION

  29. s1->G : Xcast d2, d3, d4 <data> s1->G : Xcast d3, d4 <data> s1->d2 <data> Xcast packet forwarding d4, G E d1 s1 A B D F d3, G grp: list of dest dest : next hop G : d1,d2,d3 d1 : E d2 : C d3 : D C d2, G d4 : D - Lookup for every destinations into Xcast packet - Forward a copy of the packet (with an appropriated destination list) for every distinct next hop AONL & EION

  30. In a MPLS domain, usually packets is forwarded over the LSP ending at the edge LSR associated to the packet destination paths followed by multicast packets will not be efficient Multicast tree over MPLS MPLS domain LSP ingress LSR egress LSR AONL & EION

  31. Useof the next branching node address as Destination address of IP packet no specific treatment into routers which are between branching nodes SEM packet header encapsulates Multicast group address processed by branching nodes increasing of packet length is low SEM principles AONL & EION

  32. Overhead of Xcast increases with the increasing of the number of destinations best tradeoff between path-MTU length and maximum number of destinations into a Xcast packet proposition of GXcast protocol: a generalization of Xcast partition of the set of destinations based on the optmized size of the parts how to find the best partition [still an open question] Segmentation for XCast AONL & EION

  33. AONL & EION

  34. AONL & EION

  35. IGMP is only used between hosts and first hop router; for router-to-router distribution, a routing protocol is used to build and maintain group distribution trees AONL & EION

  36. AONL & EION

  37. MOSPF, which is basically the OSPF routing protocol with extensions, makes use of the SPF (Shortest Path First) algorithm. All the other multicast protocols can be split into two types: "broadcast and prune" and "explicit join." Broadcast and prune protocols (DVMRP, PIM-DM) typically build source-specific distribution trees (fig. A) while explicit join protocols (PIM-SM, CBT) build shared trees (fig. B) from a Rendezvous Point (RP). AONL & EION

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