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

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Presentation on theme: "1 © 2004 Cisco Systems, Inc. All rights reserved. Session Number Presentation_ID IP Multicast update Apricot 2006 Toerless Eckert"— Presentation transcript:

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

2 222 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID Agenda Network Services Traditional ASM “Any Source Multicast” Source Specific Multicast (SSM) with source redundancy IPv4 multicast protocols IGMP, PIM-SM/MSDP, Bidir-PIM, PIM-SSM, … IPv6 multicast Addressing, Embedded-RP Multicast RPF ECMP, MP-BGP, IGP incongruency: one/two topologies Reliable multicast transport protocols PGM, ALC/Tornado-Codecs – content preprovisioning/nVoD

3 IP Multicast Network Services ASM, SSM, Source redundancy 333 © 2004, Cisco Systems, Inc. All rights reserved. Presentation_ID

4 444 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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 (rfc1112, ~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.

5 555 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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

6 666 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IP multicast network services Issues with ASM – resolved with SSM DoS 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” IPv4 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 (AutoRP/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

7 777 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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) IPv6 multicast (address allocation, embedded-RP)

8 IPv4 multicast protocols 888 © 2004, Cisco Systems, Inc. All rights reserved. Presentation_ID

9 999 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID Protocols for IP multicast H ost to Router signaling: membership reporting IPv4:IGMP “Internet Group Management Protocol” IPv6:MLD “Multicast Listener Discovery ” MLD = IGMP IGMPv2/MLDv1: group memberships Sufficient for ASM IGMPv3/MLDv2: group and source memberships Required for SSM, also support ASM No IGMPv2/MLDv1 report suppression: Enables tracking per-receiver on a LAN Enables null leave latency IGMPv3/MLDv2 fully backward compatible (router/host) But not snooping devices – must support IGMPv3/MLDv2! IGMPv3/MLD support in host != SSM support OS may support IGMPv3, must application may still only signaling group membership report SSM transition solutions available to map group membership reports to (S,G) channel subscriptions (eg: SSM mapping) Rcvr Membership Reports Membership Queries Router

10 10 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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 ;-( Pragmatic solution Source announces redundant source address via RIP: Easily done from application (RIP uses UDP) No protocol machinery required – only periodic sending. 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 Already used in MPEG video sourcing products Src RIP(v2) Report (UDP) Router

11 11 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID “ 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. IPv4 PIM-SM / MSDP MP-BGP(SAFI2), AutoRP/BSR Anycast-RP Protocols for IP multicast Roadmap? of IP multicast protocol evolution RPF-flooding DVMRPPIM-DM Spanning-Tree-flooding BGP CBT RPFv4v6: Multi- topologies IGP + BGP ASMv4/v6: Bidir-PIM Intradomain only SSMv4v6: PIM-SSM Intra/Interdomain ASMv6: PIM-SM+ Embedded-RP Intra/Interdomain IGPs Eg: OSPF MOSPF PAST PRESENT FUURE

12 12 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID Protocols for IP multicast IPv4 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 AutoRP 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 AutRP/BSR Typically uses static-RP config for RP announcements

13 13 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID Protocols for IP multicast IPv4 recent additions to the protocols PIM-SSM Protocol used for SSM: Built P2MP (S,G) SPT’s rooted in the source S No separate spec!. Subset of PIM-SM: No RP or RP = ! 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

14 14 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IP Protocols for IP multicast R edundant IP address policies and support Different policies possible: Anycast : clients connect to the closest instance of redundant IP address Prioritycast : clients connect to the highest- priority 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 Src B secondary /32 Rcvr 2Rcvr 1 Src A primary /31 Example: prioritycast with Prefixlength annuncement

15 IPv6 multicast 15 © 2004, Cisco Systems, Inc. All rights reserved. Presentation_ID

16 16 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IPv6 multicast Summary Everything like IPv4… ASM/SSM service models Everything PIM: PIM-SM(PIM-SSM), Bidir-PIM, (PIM-DM), BSR Except: IPv6 multicast addressing Global IPv6 multicast addresses for free (with the purchase of your IPv6 unicast addresses). Scoping is easy and free! MLDv = IGMPv No AutoRP (use BSR). No MSDP Use PIM-anycast or Prioritycast-RP for RP redundancy Use embedded-RP (IPv6 specific!) for Interdomain PIM-SM No “old BGP4”, but only MP-BGP SAFI2 Will discuss in RPF section of presentation

17 17 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IPv6 Multicast Addresses (RFC 2373) 128 bits Scope = Flags = T = 0, permanent IANA groups T= 1, FF1X::/12 -> user groups P proposed for unicast-based assignments 8 bits F PT Scope 1111 Flags group ID 0 F 1 = Interface-local 2 = Link 4 = Admin-local 5 = Site 8 = Organization E = Global

18 18 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IPv6 Unicast Based Multicast Addresses (RFC3306) FF3E:0040:3FFE:0C15:C003:1109:0000: hex Uni-pfx E hex Global 40 hex Prefix= FF | Flags | Scope | Rsvd | Plen | Network prefix | Group id Solves the old IPv4 address assignment problem: How can I get global IPv4 multicast addresses? In IPv6, if you own an IPv6 unicast address prefix you implicitly own an RFC3306 IPv6 multicast address prefix : Flags = 00PT, P = 1, T = 1=> Unicast based address SSM: Special case of unicast prefix-based addresses P=T=1, plen=0, network prefix=0 FF3x::/ 96

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

20 20 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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 IPv6 addresses - No equivalent possible in IPv4 Not usable for Bidir-PIM either ;-( RPDR R S ASM across single shared PIM domain, one Rendezvous Point

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

22 22 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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 (IPv4/IPv6) Separate topology for multicast in IGPs When asymmetric metrics are required For cost optimization Dual topologies for multicast For live-live traffic redundancy

23 23 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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 L3 link bundles – predictable traffic distribution Non-polarizing: i = i | max( hash(S, Nbr-i )) Also stable in case of link failure or unaffected flows. Multicast RPF Selection for different source addresses Given 1..n (eg: 2) ECMPs, if all routers select the same neighbor I for a source S, then polarization may happen: A rtr2 will only be joined to by rtr1 for Sources that it’s own ECMP would RPF to rtr4, but never to rtr5! Polarizing Non-Polarizing Polarizing

24 24 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IP multicast RPF BGP – IPv4 / IPv6 IPv4: MP-BGP introduced SAFI: SAFI1 = unicast only, SAFI2 = multicast only, SAFI3 = both Traditional implementations only use SAFI2 and non-SAFI BGP4 (unicast) Lazyness (not wanting to have all multicast routes in SAFI2) requires complex route- preference rules – prefer shorter prefix SAFI2 over longer prefix non-SAFI2 IPv6: Uses latest version of MP-BGP (RFC2858) 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) S R AS4AS1 AS2 AS3 Unicast only BGP SAFI2: /16 BGP4: /24

25 25 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IP multicast RPF Separate multicast topology for cost optimization Consider simplified example core/distribution network toplogy Core pops have redundant core routers, connectivity via (10Gbps) WAN links, redundant. Simple setup: A/B core routers, A/B links Regions use ring(s) for redundant connectivity Rcvr Src1 Src2 Rcvr B1 A2 B3 A1 A3 B2 Rcvr Core POP3 Core POP1 Core POP2 Region1Region2 Region3 WAN Links

26 26 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IP multicast RPF Separate multicast topology for cost optimization 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 Load splitting across WAN Links Rcvr Src1 Src2 Rcvr B1 A2 B3 A1 A3 B2 Rcvr Core POP3 Core POP1 Core POP2 Region1Region2 Region3

27 27 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IP multicast RPF Separate multicast topology for cost optimization 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 => % WAN waste (cost factor) Can not resolve problem well without multicast specific topology Unnecessary use of WAN Links Rcvr Src1 Src2 Rcvr B1 A2 B3 A1 A3 B2 Rcvr Core POP3 Core POP1 Core POP2 Region1Region2 Region3

28 28 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IP multicast RPF Separate multicast topology for cost optimization 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) Efficient use of WAN Links Rcvr Src1 Src2 Rcvr B1 A2 B3 A1 A3 B2 Rcvr Core POP3 Core POP1 Core POP2 Region1Region2 Region3

29 29 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IP multicast RPF Dual multicast topologies for resiliency Send traffic twice to different multicast groups (eg: green = , red = ) 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. Redundant Encoder/Multiplexer Redundant Decoder / Ad-Inserter/.. HFC STBs

30 30 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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 P2MP DIffserv type approach (not per flow/tree)

31 31 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID IP multicast RPF Dual multicast topologies for resiliency Topology sharing of links: Particular useful in rings. Two topologies also useful for unicast (eg: VoD 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 Redundant Encoder/Multiplexer Rcvr IGP cost in different Topologies: Unicast traffic flows in the reverse direction of unicast Small metric Infinite/large metric Multicast traffic flow Unicast traffic flow Infinite/large Small metric Multicast traffic flow Unicast traffic flow

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

33 33 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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 VoD servers, STB with HD, PC software upgrade, nVoD

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

35 35 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID Reliable multicast content carousels – before ALC/Tornado-Codecs 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 File Receive Received File

36 36 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID Reliable multicast content carousels – with ALC/Tornado-Codecs 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) File Tornado Encode Received File Receive arbitrary packets Tornado Decode

37 37 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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.

38 38 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID Reliable multicast nVoD – with ALC/Tornado-Codecs Movie 1. Segment movie: S1 = 1 min, S2 = 2 min, S3 = 4min, 8, 16, … S1 S2S3S4S5S6 2. Carousel each segment simultaneously ALC encoded At double speed: S2 S3 S4 S5 S6

39 39 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID 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. S1 S2 S3 S4 S5 S6 Reliable multicast nVoD – with ALC/Tornado-Codecs

40 40 © 2004 Cisco Systems, Inc. All rights reserved. Presentation_ID Never more traffic than unicast, never more traffic than 14 unicast user (in example) VoD 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 VoD library Zipf distribution – majority of market share Reliable multicast nVoD – with ALC/Tornado-Codecs

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

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


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