IP Multicast update Apricot 2006 Toerless Eckert Session

IP Multicast update Apricot 2006 Toerless Eckert Session Number Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. eckert@cisco. com 1

Agenda • Network Services • Traditional ASM “Any Source Multicast” • Source Specific Multicast (SSM) with source redundancy • IPv 4 multicast protocols • IGMP, PIM-SM/MSDP, Bidir-PIM, PIM-SSM, … • IPv 6 multicast • Addressing, Embedded-RP • Multicast RPF • ECMP, MP-BGP, IGP incongruency: one/two topologies • Reliable multicast transport protocols • PGM, ALC/Tornado-Codecs – content preprovisioning/n. Vo. D Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 2

IP Multicast Network Services ASM, Source redundancy Presentation_ID © 2004, Cisco Systems, Inc. All rights reserved. 3

IP Multicast Network Services ASM IP multicast service models describe how applications can send and receive multicast packets Everything application developers need to know about IP multicast (“protocol stuff is for network operators”) • ASM: Classical IP Multicast service (rfc 1112, ~1990) • Called “Any Source Multicast” today • Sources send IP multicast packets to a IP multicast group • Receivers “join to IP multicast group”. • Network will deliver packets sent by any source to an IP multicast group to all receivers that have joined the IP multicast group. Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 4

IP multicast services SSM and Source redundancy • SSM: Source Specific Multicast (~2000) • Source(s) still send IP multicast to IP multicast group address – but called “send packet to (S, G) channel”! • Receivers need to “subscribe to (S, G) channel” – indicate to network not only IP multicast group but also the source(S) !! • Network will deliver packets on a per-channel basis only • Need application based source discovery mechanisms for multi-source applications • “Redundant IP address” for source-redundancy: • Primary target for SSM: “Single-Source” – TV/Audio/Data-”broadcast” applications • Require source-redundancy – Use single IP address (with anycast/prioritycase) to avoid dynamic source-discovery • But why SSM, is ASM not good enough or better ? • ASM is simpler for application developers ! Reluctance to adopt SSM Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 5

IP multicast network services Issues with ASM – resolved with SSM • Do. S attacks by unwanted sources • Receivers can ignore packets, but network resources can only be protected by extensive network source access control == network level application control. • Address allocation • Try to get “global scope” IPv 4 multicast address (GLOB, …) – “Oh, let’s do multicast group NAT then…” • Complexity of protocol operations required • PIM-SM (Shared trees, shortest path trees, RPT/SPT switchover)/MSDP, RP announcement (Auto. RP/BSR), RP placement, RP redundancy • Operating PIM-SM over core networks (MVPN, Multicast and MPLS) • Futures: Bandwidth reservation (RSVP, per group ? Per source ? ), Link/Node Protection with PIM-SM • Scalability, Speed of protocol operations (convergence) • Operations for both SPT and RPT needed – and their interaction Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 6

IP multicast network services Summary • SSM is a key recent enhancement to IP multicast • Network operators should be very interested to use it / promote it’s use over ASM (where appropriate) to provider better (manageable/scalable) multicast services • SSM can not replace ASM in all applications • Many-source applications • Source-discovery with IP multicast • ASM and SSM can coexist • Recent means of improvement / simplification of ASM • Easier protocols for ASM • Bidir-PIM (intradomain only today) • Easier RP-redundancy (PIM-Anycast-RP, Prioritycast) • IPv 6 multicast (address allocation, embedded-RP) Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 7

IPv 4 multicast protocols Presentation_ID © 2004, Cisco Systems, Inc. All rights reserved. 8

Protocols for IP multicast Host to Router signaling: membership reporting • IPv 4: IGMP “Internet Group Management Protocol” IPv 6: MLD “Multicast Listener Discovery” • MLD<n> = IGMP<n+1> • IGMPv 2/MLDv 1: group memberships Rcvr • Sufficient for ASM • IGMPv 3/MLDv 2: group and source memberships • Required for SSM, also support ASM • No IGMPv 2/MLDv 1 report suppression: • Enables tracking per-receiver on a LAN • Enables null leave latency Membership Reports Membership Queries • IGMPv 3/MLDv 2 fully backward compatible (router/host) • But not snooping devices – must support IGMPv 3/MLDv 2! • IGMPv 3/MLD support in host != SSM support • OS may support IGMPv 3, must application may still only signaling group membership report Router • SSM transition solutions available to map group membership reports to (S, G) channel subscriptions (eg: SSM mapping) Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 9

Protocols for IP multicast Host to Router signaling: redundant source reporting • No IETF standard available • “Multicast and Anycast Group Membership” MAGMA) IETF WG never got around working on it … and is now getting isbanded ; -( Src • Pragmatic solution Source announces redundant source address via RIP: • Easily done from application (RIP uses UDP) • No protocol machinery required – only periodic sending. RIP(v 2) Report (UDP) • Fast periodic sending for fast source failure detection • All routers support RIP, but RIP is seldomnly used in production networks • Allows router to be configured to easily limit RIP to only redundant source announcements Router • Already used in MPEG video sourcing products Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 10

Protocols for IP multicast RPF-flooding PIM-DM MOSPF DVMRP Spanning-Tree-flooding CBT IPv 4 PIM-SM / MSDP “eierlegende Wollmilchsau” (german) == egg-laying wool-milk-sow (The pig that gives meat, sausage, wool, feathers, milk and eggs) Aka: the universal solution that can do everything. MP-BGP(SAFI 2), Auto. RP/BSR Anycast-RP RPFv 4 v 6: Multitopologies IGP + BGP Presentation_ID ASMv 6: PIM-SM+ Embedded-RP Intra/Interdomain © 2004 Cisco Systems, Inc. All rights reserved. ASMv 4/v 6: Bidir-PIM SSMv 4 v 6: PIM-SSM Intradomain only Intra/Interdomain PRESENT IGPs Eg: OSPF FUURE BGP PAST Roadmap? of IP multicast protocol evolution 11

Protocols for IP multicast IPv 4 ASM standard model protocols: PIM-SM / MSDP • PIM-SM • Shared-Tree and Shortest-Path-Tree Forwarding • Efficient traffic pruning in all cases • Complex operations: Register-tunnel operations, RPT/SPT switchover, RP placement, RP announcement/RP redundancy • BSR and Auto. RP • RP-annoncements • RP redundancy • MSDP • For Interdomain connecting of PIM-SM domains • Complex and set of MSDP-RPF rules. Works correctly only if MSDP overlay topology is matched with unicast/BGP routing information • For RP redundancy (“MSDP mesh-group”) – no need for MSDP-RPF check. • Anycast-RP • For RP redundancy with MSDP mesh groups – faster than Aut. RP/BSR • Typically uses static-RP config for RP announcements Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 12

Protocols for IP multicast IPv 4 recent additions to the protocols • PIM-SSM • Protocol used for SSM: Built P 2 MP (S, G) SPT’s rooted in the source S • No separate spec!. Subset of PIM-SM: No RP or RP = 0. 0 ! • Very simple: no RP == no register-tunnel/first-hop-DR, RP placement, announcement, redundancy, no RPT operations, no RPT/SPT switchover • Separate PIM-SSM spec would be 1/10 th of PIM-SM spec ? • Bidir-PIM • New PIM family protocol: Shared tree ( (*, G)) tree building only • Very good for enterprise applications with many source per group (scalability, convergence) • RP-redundancy • PIM-Anycast-RP: functions like MSDP mesh-group – without MSDP • Prioritycast-RP: Eg: for Bidir-PIM – RP redundancy without any protocol between redundant instances – because only one is active Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 13

IP Protocols for IP multicast Redundant IP address policies and support • Different policies possible: • Anycast: clients connect to the closest instance of redundant IP address Src A primary 10. 2. 3. 4/32 Src B secondary 10. 2. 3. 4/31 Rcvr 2 • Prioritycast: clients connect to the highestpriority instance of the redundant IP address • IP multicast: Redundant IP addresses for sources (SSM) and RP (PIM-SM, Bidir-PIM). • Bidir today only supports only one active RP == needs prioritycast. • Sources (video) may have different Quality – prioritycast. • Redundant IP addresses implemented by redistributing them into IGP • Anycast comes for free (closest instance = SPF) • Prioritycast requires engineering. • Elegant solution: Prefixlengths Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. Example: prioritycast with Prefixlength annuncement 14

IPv 6 multicast Presentation_ID © 2004, Cisco Systems, Inc. All rights reserved. 15

IPv 6 multicast Summary • Everything like IPv 4… • ASM/SSM service models • Everything PIM: PIM-SM(PIM-SSM), Bidir-PIM, (PIM-DM), BSR • Except: • IPv 6 multicast addressing • Global IPv 6 multicast addresses for free (with the purchase of your IPv 6 unicast addresses). • Scoping is easy and free! • MLDv<n> = IGMPv<n+1> • No Auto. RP (use BSR). • No MSDP • Use PIM-anycast or Prioritycast-RP for RP redundancy • Use embedded-RP (IPv 6 specific!) for Interdomain PIM-SM • No “old BGP 4”, but only MP-BGP SAFI 2 • Will discuss in RPF section of presentation Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 16

IPv 6 Multicast Addresses (RFC 2373) 128 bits group ID 0 1111 Flags F F P T Scope 8 bits Flags = Scope = Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. T = 0, permanent IANA groups T= 1, FF 1 X: : /12 -> user groups P proposed for unicast-based assignments 1 = Interface-local 2 = Link 4 = Admin-local 5 = Site 8 = Organization E = Global 17

IPv 6 Unicast Based Multicast Addresses (RFC 3306) • Solves the old IPv 4 address assignment problem: How can I get global IPv 4 multicast addresses? • In IPv 6, if you own an IPv 6 unicast address prefix you implicitly own an RFC 3306 IPv 6 multicast address prefix: 8 4 4 8 8 64 32 FF | Flags | Scope | Rsvd | Plen | Network prefix | Group id FF 3 E: 0040: 3 FFE: 0 C 15: C 003: 1109: 0000: 1111 3 hex Uni-pfx 40 hex Prefix=64 E hex Global Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. Flags = 00 PT, P = 1, T = 1=> Unicast based address SSM: Special case of unicast prefix-based addresses P=T=1, plen=0, network prefix=0 FF 3 x: : /96 18

Embedded Rendezvous Point Addresses • • Presentation_ID Special case of Unicast prefix based addresses Flags = 0 RPT, R = 1, P = 1, T = 1=> Rendezvous Point address embedded Rendezvous Point address = network prefix = Rpad Sixteen Rendezvous Point addresses per network prefix © 2004 Cisco Systems, Inc. All rights reserved. 19

Embedded – Rendezvous Point Usage • PIM-SM protocol operations with embedded-Rendezvous Point: • No change in PIM-SM protocol operations Just an automatic replacement to static Rendezvous Point configuration • Can replace BSR for Group-to-RP mapping • Method requires large IPv 6 addresses No equivalent possible in IPv 4 • Not usable for Bidir-PIM either ; -( ASM across single shared PIM domain, one Rendezvous Point R Presentation_ID S DR RP © 2004 Cisco Systems, Inc. All rights reserved. 20

IP multicast RPF Presentation_ID © 2004, Cisco Systems, Inc. All rights reserved. 21

IP multicast RPF Overview • RPF – Reverse Path Selection • Unlike DVMRP, PIM based multicast tree building does not come with it’s own protocol to determine the shortest paths towards an RP or a source. Instead it relies on unicast routing protocols • Initial PIM architects assumed that exactly the same routes (IGP/BGP) as for unicast could be used. And then there was reality… • Static multicast routes • ECMP (Equal Cost multipath) • Necessarily per multicast-flow, not per-packet, tailend driven • MP-BGP (MBGP) • For interdomain incongruency (IPv 4/IPv 6) • Separate topology for multicast in IGPs • When asymmetrics are required • For cost optimization • Dual topologies for multicast • For live-live traffic redundancy Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 22

IP multicast RPF ECMP – Equal cost multipath • Decision in unicast is made by upstream (sending) router • Decision in multicast is made during RPF select on downstream router. Router local choice – no network dependency • Polarizing: i = ( hash(S) % n) • . . but good for L 3 link bundles – predictable traffic distribution • Non-polarizing: i = i | max( hash(S, Nbr-i )) • Also stable in case of link failure or unaffected flows. Given 1. . n (eg: 2) ECMPs, if all routers select the same neighbor I for a source S, then polarization may happen: A rtr 2 will only be joined to by rtr 1 for Sources that it’s own ECMP would RPF to rtr 4, but never to rtr 5! Polarizing 4 5 Polarizing 6 2 Non-Polarizing 7 3 1 Multicast RPF Selection for different source addresses Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 23

IP multicast RPF BGP – IPv 4 / IPv 6 • IPv 4: MP-BGP introduced SAFI: • SAFI 1 = unicast only, SAFI 2 = multicast only, SAFI 3 = both • Traditional implementations only use SAFI 2 and non-SAFI BGP 4 (unicast) • Lazyness (not wanting to have all multicast routes in SAFI 2) requires complex routepreference rules – prefer shorter prefix SAFI 2 over longer prefix non-SAFI 2 • IPv 6: Uses latest version of MP-BGP (RFC 2858) • No non-SAFI route announcements (never defined), no SAFI 3 (removed by IETF) Only SAFI 1 for unicast, SAFI 2 for multicast • Should never use SAFI 1 routes for multicast to keep RPF rules simple (and to use MP-BGP as intended by wording of BGP spec) AS 3 BGP 4: 131. 188. 1. 0/24 Unicast only R AS 1 AS 4 AS 2 Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. BGP SAFI 2: 131. 188. 0. 0/16 131. 188. 1. 1 S 24

IP multicast RPF Separate multicast topology for cost optimization Rcvr Src 1 Rcvr A 2 B 1 Core Region 1 POP 1 Core POP 2 Region 2 Src 2 Rcvr WAN Links A 1 B 2 Rcvr A 3 Rcvr B 3 Core POP 3 Rcvr Region 3 Rcvr • Consider simplified example core/distribution network toplogy • Core pops have redundant core routers, connectivity via (10 Gbps) WAN links, redundant. Simple setup: A/B core routers, A/B links • Regions use ring(s) for redundant connectivity Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 25

IP multicast RPF Separate multicast topology for cost optimization Rcvr Src 1 Rcvr A 2 B 1 Core Region 1 POP 1 Core POP 2 Region 2 Src 2 Rcvr A 1 B 2 Rcvr Load splitting across WAN Links A 3 Rcvr B 3 Core POP 3 Rcvr Region 3 Rcvr • IGP metric are set to achieve good load distribution across redundant core. • Manual IGP metric setting and/or tools • Assume in the idealized topology cost of 1 on all links. • Result: Unicast traffic is load split across redundant core links Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 26

IP multicast RPF Separate multicast topology for cost optimization Rcvr Src 1 Rcvr A 2 B 1 Core Region 1 POP 1 Core POP 2 Region 2 Src 2 Rcvr A 1 B 2 Rcvr Unnecessary use of WAN Links A 3 Rcvr B 3 Core POP 3 Rcvr Region 3 Rcvr • The same metric good for unicast load splitting cause multicast traffic to go unnecessarily across both the A and B WAN links. • 10 Gbps WAN links, 1. . 2 Gbs multicast => 10. . 20% WAN waste (cost factor) • Can not resolve problem well without multicast specific topology Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 27

IP multicast RPF Separate multicast topology for cost optimization Rcvr Src 1 Rcvr A 2 B 1 Core Region 1 POP 1 Core POP 2 Region 2 Src 2 Rcvr A 1 B 2 Rcvr Efficient use of WAN Links A 3 Rcvr B 3 Core POP 3 Rcvr Region 3 Rcvr • Simple? to minimize tree costs with a multicast specific topology • Manual or tool based • Example toplogy: make B links very expensive for multicast (cost 100), so they are only us as last resort (no A connectivity) Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 28

IP multicast RPF Dual multicast topologies for resiliency STBs HFC Redundant Encoder/Multiplexer Redundant Decoder / Ad-Inserter/. . • Send traffic twice to different multicast groups (eg: green = 232. 1. 0. 1, red = 232. 1. 0. 2) • Use path separation in network to pass red/green across different paths Note: dual topologies just one solution (VRFs, virtual routers, …) • Receivers receive both copies, remove duplicates by sequence numbers (eg: MPEG timestamp). • No single network failure will cause any service interruption • Same bandwidth allocation needed as in traditional SONET rings, but solution even better: 0 loss instead of 50 msec. Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 29

IP multicast RPF Dual multicast topologies for resiliency • Traditional application: • Market data distribution in finance network (NASDAQ, etc. . ) • Based on two completely separate networks ! • With two topology solution • No separate physical networks required • Can provide different subsets of the network to different classes of traffic. • Can share links to reduce cost (two unidirection links). • Can share nodes to reduce cost. • Vs virtual routers or similar “virtual network”: • No need for subnet encaps ifor multiple topologies • Vs. RSVP-TE P 2 MP • DIffserv type approach (not per flow/tree) Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 30

IP multicast RPF Dual multicast topologies for resiliency Rcvr IGP cost in different Topologies: Rcvr Unicast traffic flows in the reverse direction of unicast Rcvr Redundant Encoder/Multiplexer Rcvr • Topology sharing of links: Rcvr Unic as ffic t tra flow Small metric flow ffic flow a r t ffic st a a r t c i t t as Mul Unic flow ffic a r t st tica Mul Infinite/large metric • Two topologies also useful for Small metric • Particular useful in rings. unicast (eg: Vo. D load splitting) • Requires unidirectionaly “infinite” link metric to avoid reconvergence of topologies (if wanted) • Available in ISIS today, not in OSPF • Part of OSPF/UDLR draft in IETF Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 31

Reliable multicast transport protocols Presentation_ID © 2004, Cisco Systems, Inc. All rights reserved. 32

Reliable Multicast Overview • PGM (Pragmatic Generic Multicast) • Near-real-time delivery with TCP compliant flow-control, optional network level scalability support (DLR, NE) • NAK-based: Preferred to small to mid-size receiver groups with tight delivery schedules • Used in many finance/comerical applications today, supported by Windows-XP and later, etc. Router support little used. • ALC (Asynchronuous Layered Codec) • Non-real-time delivery without any feedback from receivers – can support arbitrary large receiver population (eg: STBs). • Relies on FEC. Interesting with “Tornado Codecs” (large block codecs. • Target applications eg: Content Distribution to Vo. D servers, STB with HD, PC software upgrade, n. Vo. D Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 33

Reliable multicast PGM components Server PGM (Server/Source) Stack Network Optional PGM functions DLR: Designated Local Repairer Network Element = Router Assist Host PGM (Host/Receiver) Stack Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 34

Reliable multicast content carousels – before ALC/Tornado-Codecs File Received File • In a traditional carousel, a file is repeatedly sent, receivers start receiving in the middle receive the tail of the file and then continue to receive until they have received the head of the next iteration. • Works only well if network has little packet loss • Need to potentially receive content for many iterations in face of higher packet loss Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 35

Reliable multicast content carousels – with ALC/Tornado-Codecs File Tornado Encode Receive arbitrary packets Tornado Decode Received File • ALC encodes file into eg: 2^32 different packets. • Receiver needs to receive just sufficiently many arbitrary packet from encoding to reconstruct file (original file size +5% overhead) Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 36

Reliable multicast content carousels – with ALC/Tornado-Codecs • Allows to carry reliable multicast content as scavenger class traffic (less than best effort). • Use free bandwidth in network ! • Limit of basic carousel: • Can only start encoding after whole file is available • Not directly usable for real-time transmission • Break up file into segments, apply ALC encoding separately, start transmission after first segment. Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 37

Reliable multicast n. Vo. D – with ALC/Tornado-Codecs Movie 1. Segment movie: S 1 = 1 min, S 2 = 2 min , S 3 = 4 min, 8, 16, … S 2 S 3 S 4 S 5 S 6 2. Carousel each segment simultaneously ALC encoded At double speed: S 1 S 2 S 3 S 4 S 5 S 6 Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 38

Reliable multicast n. Vo. D – with ALC/Tornado-Codecs S 1 S 2 S 3 S 4 S 5 S 6 3. Receiver IGMP joins to one segment at a time. Once segment is fully received, it is decoded and receiver receives next segment. Because segments are transmitted faster than realtime (example: factor 2), playout takes as long as receiving next segment. Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 39

Reliable multicast n. Vo. D – with ALC/Tornado-Codecs • Never more traffic than unicast, never more traffic than 14 unicast user (in example) • Vo. D starts after 30 seconds • Total bandwidth in network is 7 segments * double speed == same bandwidth as 14 unicast VOD viewers require. • As soon as more than 14 user watch same content (independent of their starting time), no more bandwidth is required. • If less than 14 users watch, bandwidth utilized is still the same as in unicast (because only traffic joined to by IGMP is being forwarded). • Just transmission is more bursty than unicast ! • Parameters can easily be varied • Beneficial for top 3? % of Vo. D library Zipf distribution – majority of market share Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 40

Questions ? Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 41

Presentation_ID © 2003, Cisco Systems, Inc. All rights reserved. 42