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IS-IS Extension for Building Distribution Trees

This draft proposes an extension to the IS-IS protocol to build distribution trees for multicast transport. It aims to address the limitations of existing protocols and solutions, such as PIM, in supporting overlay applications and network virtualization overlays.

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IS-IS Extension for Building Distribution Trees

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  1. IS-IS Extension For Building Distribution Treesdraft-yong-isis-ext-4-distribution-tree-01 Lucy Yong, WeiguoHao, Donald Eastlake Andrew Qu, Jon Hudson November 2013 Vancouver BC

  2. Problem Statement • IP network doesn't yet support multicast transport • IP network relies on PIM protocols and solutions to carry multi-destination traffic • Pain points in PIM protocol solutions: • Use own “hello” protocol and hop-by-hop message • Additional convergence time besides IGP’s • A lot of soft state and heavy CPU load • Packet may be forwarded to RP unnecessarily • Scalability Challenges to support overlay applications

  3. Problem Statement Cont. • PIM solutions hardly meet the requirements for network virtualization overlays, i.e. [NVO3] • IP as underlying network may carry many overlay VNs that contain some BUM traffic • A VN maps to an IP multicast group, PIM can’t scale to • A VN topology may be spare and dynamic compared to underlying network topology • Massive PIM states burden the device • Slow convergence time for multicast traffic • Major impacts to VNs and cloud applications • Overlay VN BUM traffic may be carried as underlying unicast traffic • May waste massive network capacity due to replications • Increase the cost on the applications

  4. IS-IS Extension for Multicast Transport • IS-IS has been used for unicast traffic routing • Can be for multicast traffic routing as well, like TRILL • Simple IS-IS extension can achieve: • Build distribution rooted-trees for multicast transport • The benefits to do this: • One protocol for both unicast and multicast transport • Use of LSDB and SPF algorithm to build a tree • Same convergence time for both unicast and multicast • Forwarding Optimization • Well align with network evolution direction, create programmable, self-healing, multi-service fabric • In the fabric, a closed IP network carry all types of traffic under one control plane protocol

  5. ISIS based Rooted Distribution Trees ES1 • Provision tree root and associated (*,G) at a node • ISIS distributes tree root/(* G) in IGP • Nodes compute the trees with SPF/LSDB • Supports ECMP and allow multiple rooted trees associated w/ (*, G) ES3 R2 R7 L3 L2 R10 L1 R5 R8 R3 R1 R6 R11 R9 R4 ES4 ES5 ES2 R1&R7 are the root of red and green trees ES1、ES2、ES5 is the end station of Group1, ES3、ES4 is the end station of Group2 Group1 uses red tree and Group2 uses green

  6. Distribution Tree Pruning for (*, G) R1 L1 ES5 R2 R4 ES1 R9 ES2 Pruning red tree for Group1 • Edge Routers use IGMP to learn host interested (*,G) or (S, *G) • Edge routers announce their interested (*,G) • Each router prunes the tree based on other edge router’s interests on the (*, G) /(S,G) • Multi-destination traffic for a group is forwarded over the pruned tree for the group R7 R10 R2 L3 R1 L1 ES1 ES1 R4 Pruning green tree for Group2

  7. IGP Multi-Level Support Backbone Area A Area Z • The solution needs to work under multi-levels configuration • Multicast source(s) and listeners may be in any area, respectively • A tree root node associated multicast groups may be in any area • The distributed tree spans across all other areas via BR • Loop prevention is must • Single designated BR is selected for (*, G) • Level optimization is possible • If an area doesn’t have any interested members, the pruned tree may not have any branch in the area. IGP Leve1 IGP Level2 IGP Level1 BR1 BR3 BR2 BR4

  8. IGP Multi-Level Support Backbone Area A Area Z IGP Leve1 IGP Level2 IGPlLevel1 BR1 BR3 BR2 BR4 IGPleve1 IGP Level2 IGPlevel1 Area A Backbone Area Z BR1 BR3 BR2 BR4 Build a distribution tree in area A only

  9. Transport Overlay VN BUM Traffic in IGP • Designated edge/boarder Routers (DR) maintains the mapping between the VN (*, G) to a underlying (*,G) • DRs perform packet encaps/descap upon receiving a packet from a host or the underlying network • Mapping of the VN (*, G) and a underlying (*,G) at DR • manually configured at DRs • automatically generated • dynamically informed • The same edge/boarder router MUST be selected as the Designated Router for the VN (*, G) and the underlying (*,G) that are mapped

  10. Next Step • Seek some comments and feedbacks • Should we add this work item to the WG? Huawei has the solution demo in the Bits-n-Bytes event on Thur. 7pm. Welcome to visit and comment

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