Sprint Cisco. Agenda. Special Thanks To. For their contribution of slides

Transcription

1 Svensk Tele Utveckling & Produkt Innovation AB A company with its HQ in an outhouse located in Karlstad, Sweden Peter Löthberg, <roll@stupi.se> , e164.net 1 Agenda IP Multicast Technology and Concepts IP Multicast Host-to-Router Protocols IP Multicast forwarding IP Multicast Routing Protocols Multiprotocol BGP Multicast source discovery protocol Source Specific Multicast Exchange points using S 2 Special Thanks To Sprint Cisco For their contribution of slides 3 1

2 Introduction to Multicast Why multicast? When sending same data to multiple receivers Better bandwidth utilization Lesser host/router processing Receivers addresses unknown Applications Video/audio conferencing Resource discovery/service advertisement Stock distribution Eg. Vat, Vic, IP/TV, Pointcast Public Radio & TV distribution 4 Unicast vs. Multicast Unicast Server Router Multicast Server Router 5 Multicast Advantages Enhanced Efficiency: Controls network traffic and reduces server and CPU loads Optimized Performance: Eliminates traffic redundancy Distributed Applications: Makes multipoint applications possible Multicast Unicast 0.8 Traffic Mbps Example: Audio Streaming All clients listening to the same 8 Kbps audio # Clients 6 2

3 IP Multicast Service Model RFC 1112 Each multicast group identified by a class-d IP address Members of the group could be present anywhere in the Internet Members join and leave the group and indicate this to the routers Senders and receivers are distinct: i.e., a sender need not be a member Routers listen to all multicast addresses and use multicast routing protocols to manage groups 7 IP Multicast addressing IP group addresses Class D address high-order 3 bits are set ( ) Range from through Well known addresses designated by IANA Reserved use: through all multicast systems on subnet all routers on subnet Transient addresses, assigned and reclaimed dynamically Global scope: Limited Scope: Site-local scope: /16 Organization-local scope: /14 8 Multicast Addressing IP Multicast Group Addresses Class D Address Space High order bits of 1st Octet = 1110 Reserved Link-local Addresses Transmitted with TTL = 1 Examples: All systems on this subnet All routers on this subnet DVM routers OSPF routers PIMv2 Routers 9 3

4 Multicast Addressing Static Group Address Assignment Temporary method to meet immediate needs Group range: Your AS number is inserted in middle two octets Remaining low-order octet used for group assignment Defined in RFC 2770 (GLOP) Provides each AS with /24 addresses to use while waiting another solution Source Specific multicast - Group range: Multicast Addressing IP Multicast MAC Address Mapping (FDDI and Ethernet) 5 Bits Lost Bits 28 Bits e-7f Bits 23 Bits 48 Bits 11 Multicast Addressing IP Multicast MAC Address Mapping (FDDI & Ethernet) Be Aware of the 32:1 Address Overlap 32 - IP Multicast Addresses Multicast MAC Address (FDDI and Ethernet) 0x0100.5E

5 Multicast Addressing IP Multicast MAC Address Mapping (Token Ring) Be Aware of the 268,435,200:1 Address Overlap ALL 268,435,200 - IP Multicast Addresses Multicast MAC Address (Token Ring) 0xFFFF.FFFF.FFFF RUN AWAY!!! 13 Agenda IP Multicast Technology and Concepts IP Multicast Host-to-Router Protocols IP Multicast forwarding IP Multicast Routing Protocols Multiprotocol BGP Multicast source discovery protocol Source Specific Multicast Exchange points using S 14 IP Multicast Service Model Host-to-Router Protocols (IGMP) Hosts Routers Multicast Routing Protocols (PIM) 15 5

6 Host-Router Signaling: IGMP How hosts tell routers about group membership Routers solicit group membership from directly connected hosts RFC 1112 specifies version 1 of IGMP Supported on Windows 95 RFC 2236 specifies version 2 of IGMP Supported on latest service pack for Windows and most UNIX systems IGMP version 3 is specified in IETF draft draft-ietf-idmr-igmp-v3-03.txt 16 Host-Router Signaling: IGMP Joining a Group H1 H H3 Report Host sends IGMP Report to join group 17 Host-Router Signaling: IGMP Maintaining a Group X H1 H2 H3 X Suppressed Report Suppressed Query Router sends periodic Queries to One member per group per subnet reports Other members suppress reports 18 6

7 Host-Router Signaling: IGMP Leaving a Group (IGMPv1) H1 H2 H3 #1 General Query Host quietly leaves group Router sends 3 General Queries (60 secs apart) No IGMP Report for the group is received Group times out (Worst case delay ~= 3 minutes) #2 19 Host-Router Signaling: IGMP H1 Leaving a Group (IGMPv2) # Leave to H3 Group Specific Query to #2 Host sends Leave message to Router sends Group specific query to No IGMP Report is received within ~3 seconds Group times out H2 20 IGMPv3 draft-ietf-idmr-igmp-v3-03.txt Early implementations now in beta Enables hosts to listen only to a specified subset of the hosts sending to a group Enables hosts to exclude a specific host sending to a group 21 7

8 IGMPv3 Source = Group = R1 R2 Source = Group = H1 wants to receive from S = but not from S = With IGMP, specific sources can be pruned back - S = in this case R3 IGMPv3: Join , Leave , H1 - Member of Agenda IP Multicast Technology and Concepts IP Multicast Host-to-Router Protocols IP Multicast forwarding IP Multicast Routing Protocols Multiprotocol BGP Multicast source discovery protocol Source Specific Multicast 23 Multicast Forwarding Multicast Routing is backwards from Unicast Routing Unicast Routing is concerned about where the packet is going. Multicast Routing is concerned about where the packet came from. Multicast Routing uses Reverse Path Forwarding 24 8

9 Multicast Routing Protocols (Reverse Path Forwarding) What is F? A router forwards a multicast datagram if received on the interface used to send unicast datagrams to the source Unicast Receiver B C Source A F D E Reverse Unicast Path Multicast 25 Multicast Routing Protocols (Reverse Path Forwarding) If the F check succeeds, the datagram is forwarded If the F check fails, the datagram is typically silently discarded When a datagram is forwarded, it is sent out each interface in the outgoing interface list Packet is never forwarded back out the F interface! 26 Multicast Forwarding Example: F Checking Source F Check Fails Packet arrived on wrong interface! Mcast Packets 27 9

10 Agenda IP Multicast Technology and Concepts IP Multicast Host-to-Router Protocols IP Multicast forwarding IP Multicast Routing Protocols Multiprotocol BGP Multicast source discovery protocol Source Specific Multicast 28 Multicast Routing Protocols Characteristics Shortest Path or Source Distribution Tree Source Notation: (S, G) S = Source G = Group A B D F C E Receiver 1 Receiver 2 29 Multicast Routing Protocols Characteristics Shared Distribution Tree Source 1 Notation: (*, G) * = All Sources G = Group A B D (Shared Root) F Source 2 C E Receiver 1 Receiver

11 Multicast Routing Protocols Characteristics Distribution trees Source tree Uses more memory O(S x G) but you get optimal paths from source to all receivers, minimizes delay Shared tree Protocols Uses less memory O(G) but you may get suboptimal paths from source to all receivers, may introduce extra delay PIM, DVM, MOSPF, CBT 31 Multicast Routing Protocols Characteristics Types of multicast protocols Dense-mode Broadcast and Prune behavior Similar to Radio broadcast Sparse-mode Explicit Join behavior Similar to Pay Per View 32 Multicast Routing Protocols Characteristics Dense-mode protocols Assumes dense group membership Branches that are pruned don t get data Pruned branches can later be grafted to reduce join latency DVM Distance Vector Multicast Routing Protocol Dense-mode PIM Protocol Independent Multicast 33 11

12 Multicast Routing Protocols Characteristics Sparse-mode protocols Assumes group membership is sparsely populated across a large region Uses either source or shared distribution trees Explicit join behavior assumes no one wants the packet unless asked Joins propagate from receiver to source or Rendezvous Point (Sparse mode PIM) or Core (Core-Based Tree) 34 Explicit join model Sparse Mode PIM Receivers join to the Rendezvous Point () Senders register with the Data flows down the shared tree and goes only to places that need the data from the sources Last hop routers can join source tree if the data rate warrants by sending joins to the source F check for the shared tree uses the F check for the source tree uses the source 35 Sparse Mode PIM Only one is chosen for a particular group statically configured or dynamically learned (Auto-, PIM v2 candidate advertisements) Data forwarded based on the source state (S, G) if it exists, otherwise use the shared state (*, G) 36 12

13 Sparse Mode PIM Source Link Data Control A B D C E Receiver 1 Receiver 2 37 Sparse Mode PIM Source Receiver 1 Joins Group G C Creates (*, G) State, Sends (*, G) Join to the A B Join D C E Receiver 1 Receiver 2 38 Sparse Mode PIM Source Creates (*, G) State A B D C E Receiver 1 Receiver

14 Sparse Mode PIM Source Source Sends Data A Sends Registers to the Register A B D C E Receiver 1 Receiver 2 40 Sparse Mode PIM Source De-Encapsulates Registers Forwards Data Down the Shared Tree Sends Joins Towards the Source Join Join A B D C E Receiver 1 Receiver 2 41 Sparse Mode PIM Source Sends Register-Stop Once Data Arrives Natively Register-Stop A B D C E Receiver 1 Receiver

15 Sparse Mode PIM Source C Sends (S, G) Joins to Join the Shortest Path (SPT) Tree (S, G) Join A B D C E Receiver 1 Receiver 2 43 Sparse Mode PIM Source When C Receives Data Natively, It Sends Prunes Up the tree for the Source. Deletes (S, G) OIF and Sends Prune Towards the Source (S, G) Prune A B D (S, G) Bit Prune C E Receiver 1 Receiver 2 44 Sparse Mode PIM Source New Receiver 2 Joins E Creates State and Sends (*, G) Join A B D (*, G) Join C E Receiver 1 Receiver

16 Sparse Mode PIM Source C Adds Link Towards E to the OIF List of Both (*, G) and (S, G) Data from Source Arrives at E A B D C E Receiver 1 Receiver 2 46 PIM Sparse Mode Source NOTE: still important! Required to support sources which arrive later or are not known by application. A B D Source 2 C E Receiver 1 also: - announces active sources via MSDP - identifies group modality - serves as root for bidir 47 Agenda IP Multicast Technology and Concepts IP Multicast Host-to-Router Protocols IP Multicast forwarding IP Multicast Routing Protocols Multiprotocol BGP Multicast source discovery protocol Source Specific Multicast Exchange points using S 48 16

17 MBGP Summary Solves part of inter-domain problem Can exchange multicast routing information Uses standard BGP configuration knobs Permits separate unicast and multicast topologies if desired Still must use PIM to: Build distribution trees Actually forward multicast traffic PIM-SM recommended But how do domains learn about each remote sources? 49 MBGP Multiprotocol BGP MBGP overview MBGP capability negotiation MBGP NLRI exchange MBGP-DVM redistribution Unicast to Multicast NLRI Translation 50 MBGP Overview MBGP: Multiprotocol BGP (aka multicast BGP in multicast networks) Defined in RFC 2283 (extensions to BGP) Can carry different types of routes Unicast Multicast Both routes carried in same BGP session Does not propagate multicast state info Same path selection and validation rules AS-Path, LocalPref, MED, 51 17

18 MBGP Overview New multiprotocol attributes MP_REACH_NLRI MP_UNREACH_NLRI MP_REACH_NLRI and MP_UNREACH_NLRI Address Family Information (AFI) = 1 (IPv4) Sub-AFI = 1 (NLRI is used for unicast) Sub-AFI = 2 (NLRI is used for multicast F check) Sub-AFI = 3 (NLRI is used for both unicast and multicast F check) 52 MBGP Overview The BGP UPDATE Message Unfeasible Routes Length (2 Octets) Withdrawn Routes (Variable) Total path Attribute Length (2 Octets) Path Attributes (Variable) Network Layer Reachability Information (Variable) Length (I Octet) Prefix (Variable) Attribute Type Attribute Length Attribute Value Length (I Octet) Prefix (Variable) A BGP update is used to advertise a single feasible route to a peer, or to withdraw multiple unfeasible routes Each update message contains attributes, like origin, AS-Path, Next-Hop,. MP_REACH_NLRI 53 MBGP Overview MP_REACH_NLRI Attribute Address Family Identifier (2 Octets) Subsequent Address Family Identifier (1 Octet) Length of the Next-Hop Address (1 Octet) Network Address of Next-Hop (Variable) Number of SNPAs (1 Octet) Length of first SNPA (1 Octet) First SNPA (Variable) Length of second SNPA (1 Octet) Second SNPA (Variable). Length of last SNPA (1 Octet) Last SNPA (Variable) Network Layer Reachability Information (Variable) RFC 1700 May be Zero Length (I Octet) Prefix (Variable) 54 18

19 MBGP Overview MP_UNREACH_NLRI Attribute Address Family Identifier (2 Octets) Subsequent Address Family Identifier (1 Octet) Withdrawn Routes (Variable) Length (I Octet) Prefix (Variable) 55 MBGP Overview Separate BGP tables maintained Unicast Routing Information Base (RIB) Multicast Routing Information Base (MRIB) Unicast RIB (U-RIB) Contains unicast prefixes for unicast forwarding Populated with BGP unicast NLRI AFI = 1, Sub-AFI = 1 or 3 Multicast RIB (M-RIB) Contains unicast prefixes for F checking Populated with BGP multicast NLRI AFI = 1, Sub-AFI = 2 or 3 56 MBGP Overview MBGP allows different unicast and multicast topologies and different policies Same IP address may have different signification Unicast routing information Multicast F information For same IPv4 address two different NLRI with different next-hops Can use existing or new BGP peering topology for multicast 57 19

20 MBGP Capability Negotiation BGP routers establish BGP sessions through the OPEN message OPEN message contains optional parameters BGP session is terminated if OPEN parameters are not recognised New parameter: CAPABILITIES Multiprotocol extension Multiple routes for same destination 58 MBGP Capability Negotiation New keyword on neighbor command neighbor <foo> remote-as <asn> nlri multicast unicast Configures router to negotiate either or both NLRI If neighbor configures both or subset, common NRLI is used in both directions If there is no match, notification is sent and peering doesn t come up 59 MBGP Capability Negotiation If neighbor doesn t include the capability parameters in open, back off and reopen with no capability parameters Peering comes up in unicast-only mode 60 20

21 MBGP Capability Negotiation AS 123 BGP Session for Unicast and Multicast NLRI /24.2 AS 321 Receiver BGP: open active, local address BGP: went from Active to OpenSent BGP: sending OPEN, version /24 BGP: OPEN rcvd, version 4 BGP: rcv OPEN w/option parameter type: 2, len: 6 BGP: OPEN has CAPABILITY code: 1, length 4 BGP: OPEN has MP_EXT CAP for afi/safi: 1/1 Sender BGP: rcv OPEN w/option parameter type: 2, len: 6 BGP: OPEN has CAPABILITY code: 1, length 4 BGP: OPEN has MP_EXT CAP for afi/safi: 1/2 BGP: went from OpenSent to OpenConfirm BGP: went from OpenConfirm to Established 61 MBGP NLRI Information Congruent Topologies AS 123 BGP Session for Unicast and Multicast NLRI /24.2 AS /24 router bgp 321 neighbor remote-as 123 nlri unicast multicast network nlri unicast multicast no auto-summary /24 Receiver Sender 62 MBGP NLRI Information Congruent Topologies AS 123 BGP Session for Unicast and Multicast NLRI /24.2 AS /24 Receiver Unicast Information NLRI: /24 AS_PATH: 321 MED: Next-Hop: Multicast Information MP_REACH_NLRI: /24 AFI: 1, Sub-AFI: 2 (multicast) AS_PATH: 321 MED: Next-Hop: Routing Update Sender /

22 MBGP NLRI Information Incongruent Topologies AS Unicast Traffic /24.2 AS Multicast Traffic / /24 router bgp network nlri unicast multicast neighbor remote-as 123 nlri unicast neighbor remote-as 123 nlri multicast Sender 64 MBGP NLRI Information Incongruent Topologies AS Unicast Traffic /24.2 AS Multicast Traffic / /24 Unicast Information Sender NLRI: /24 AS_PATH: 321 MED: Next-Hop: Routing Update 65 MBGP NLRI Information Incongruent Topologies AS Unicast Traffic /24.2 AS Multicast Traffic / /24 Multicast Information Sender MP_REACH_NLRI: /24 AFI: 1, Sub-AFI: 2 AS_PATH: 321 MED: Next-Hop: Routing Update 66 22

23 MBGP NLRI Information Incongruent Topologies AS Unicast Traffic /24.2 AS Multicast Traffic / /24 Unicast RIB Network Next-Hop Path / Sender Multicast RIB Network Next-Hop Path / MBGP NLRI Information Unicast RIB Network Next-Hop Path *>i / i *>i / i Multicast RIB Network Next-Hop Path D /24 D /24 D /24 R /16 S /24 Route Table router bgp 100 network network no auto-summary nlri unicast nlri unicast New nlri keyword used to control RIB population. (e.g. network command) Unicast RIB only 68 MBGP NLRI Information Unicast RIB Network Next-Hop Path Multicast RIB Network Next-Hop Path *>i / i *>i / i D /24 D /24 D /24 R /16 S /24 Route Table router bgp 100 network network no auto-summary nlri multicast nlri multicast New nlri keyword used to control RIB population. (e.g. network command) Unicast RIB only Multicast RIB only 69 23

24 MBGP NLRI Information Unicast RIB Network Next-Hop Path *>i / i *>i / i Multicast RIB Network Next-Hop Path *>i / i *>i / i D /24 D /24 D /24 R /16 S /24 Route Table router bgp 100 network network no auto-summary nlri unicast multicast nlri unicast multicast New nlri keyword used to control RIB population. (e.g. network command) Unicast RIB only Multicast RIB only Both RIB s 70 MBGP Summary Solves part of inter-domain problem Can exchange multicast routing information Uses standard BGP configuration knobs Permits separate unicast and multicast topologies if desired Still must use PIM to: Build distribution trees Actually forward multicast traffic PIM-SM recommended But there s still a problem using PIM-SM here (more on that later) 71 Agenda IP Multicast Technology and Concepts IP Multicast Host-to-Router Protocols IP Multicast forwarding IP Multicast Routing Protocols Multiprotocol BGP Multicast source discovery protocol Source Specific Multicast Exchange points using S 72 24

25 MSDP Concept Simple but elegant Utilize inter-domain source trees Reduces problem to locating active sources or receiver last-hop can join inter-domain source tree 73 MSDP Concept Simplify Interdomain problem: Utilize inter-domain source trees Reduces problem to locating active sources or receiver last-hop can join inter-domain source tree 74 MSDP Concepts Works with PIM-SM only s knows about all sources in a domain Sources cause a PIM Register to the Can tell s in other domains of its sources Via MSDP SA (Source Active) messages s know about receivers in a domain Receivers cause a (*, G) Join to the can join the source tree in the peer domain Via normal PIM (S, G) joins 75 25

26 MSDP Design Points MSDP peers talk via TCP connections Source Active (SA) messages Peer-F forwarded to prevent loops F check on AS-PATH back to the peer other rules from draft apply If successful, flood SA message to other peers Stub sites can be configured to accept all SA messages (similar to static default for routing) Since they have only one exit (e.g., default peer) MSDP speaker may cache SA messages Reduces join latency 76 MSDP Peers MSDP establishes a neighbor relationship between MSDP peers Peers connect using TCP port 639 Peers send keepalives every 60 secs (fixed) Peer connection reset after 75 seconds if no MSDP packets or keepalives are received MSDP peers must run BGP! May be an MBGP peer, a BGP peer or both Exception: BGP is unnecessary when peering with only a single MSDP peer. 77 MSDP Overview MSDP Peers MSDP Example Domain E Source Active Messages SA Domain C SA r Domain B SA SA SA Join (*, ) SA SA Message , SA s Domain A SA Message , Domain D Register ,

27 MSDP Overview MSDP Peers MSDP Example Domain E Domain C r Domain B Join (S, ) Domain D s Domain A 79 MSDP Overview MSDP Peers MSDP Example Domain E Multicast Traffic Domain C r Domain B Domain D s Domain A 80 MSDP Overview MSDP Example MSDP Peers Multicast Traffic Domain B Domain C Domain E Join (S, ) r Domain D s Domain A 81 27

28 MSDP Overview MSDP Example MSDP Peers Domain E Multicast Traffic Domain C r Domain B Domain D s Domain A 82 MSDP SA Messages MSDP SA Message Contents One or more messages (in TLV format) Keepalives Source Active (SA) Messages Source Active Request (SA-Req) Messages Source Active Response (SA-Resp) Message Source Active (SA) Messages Used to advertise active Sources in a domain Can also carry initial multicast packet from source Hack for Bursty Sources (ala SDR) SA Message Contents: IP Address of Originator (usually an ) Number of (S, G) s pairs being advertised List of active (S, G) s in the domain Encapsulated Multicast packet 83 MSDP SA Messages MSDP Message Contents (cont.) SA Request (SA-Req) Messages Used to request a list of active sources for a group Sent to an MSDP SA Cache Server Reduces Join Latency to active sources SA Request Messages contain: Requested Group Address SA Response (SA-Resp) Messages Sent in response to an SA Request message SA Response Messages contain: IP Address of Originator (usually an ) Number of (S, G) s pairs being advertised List of active (S, G) s in the domain Keepalive messages Used to keep MSDP peer connection up 84 28

29 Receiving SA Messages Skip F Check and process SA if: Sending MSDP peer = only MSDP peer (i.e. the default-peer or only msdp-peer configured.) Sending MSDP peer = Mesh-Group peer F Check the received SA message. Lookup best BGP path to in SA message Search MBGP RIB first then BGP RIB If path to not found, F Check Fails; ignore SA message Sending MSDP Peer = BGP peer? Yes: Is best path to via this BGP peer? If yes, F Check Succeeds; process SA message No: Is next AS in best path to = AS of MSDP peer? If yes, F Check Succeeds; process SA message 85 MSDP Application Anycast draft-ietf-mboned-anycast-rp-05.txt Within a domain, deploy more than one for the same group range Give each the same IP address assignment Sources and receivers use closest May be used intra-domain (enterprise) to provide redundancy and load sharing 86 MSDP Application Anycast Sources from one are known to other s using MSDP When an goes down, sources and receivers are taken to new via unicast routing Fast convergence 87 29

30 Anycast Convergence Src Rec X Rec Rec MSDP Rec Src Anycast Convergence Src Rec X Rec Rec Rec Src 89 Sprint PIM-Sparse Mode Deployment Seattle Pennsauken PIM-SM Deployment San Jose Stockton Fortworth DC Six (6) Rendezvous Points Cisco GSRs running IOS Ver 12.0S Full Mesh MSDP Peering between s 90 30

31 ISP Requirements to Deploy Now Want an explicit join protocol for efficiency PIM-SM (forwarding) Use existing (unicast) operation model MBGP (routing) Need interdomain source discovery MSDP (source discovery) 91 Customer Configuration -- Scenario 1 H1 H2 H3 CPE Sprint Network (MSDP Peering between s) Scenario 1 -- Customer uses Sprintlinks s Static or MBGP to inject sources (F_check) PIM-SM for Signaling with Sprint s 92 Configuring PIM Sparse Mode ip multicast-routing E0 S0 interface Ethernet 0 ip address ip pim sparse-mode interface Serial 0 ip address ip pim sparse-mode ip pim rp-address ip pim accept-rp Really simple to configure Requires one additional command to configure the rendezvous point in the ISP 93 31

32 Customer Configuration -- Scenario 2 H1 CPE functions as R2 R1 Sprint Network (MSDP Peering between s) R3 Scenario 2 -- Customer uses own and MSDP Static or MBGP to inject sources (F_check) PIM-SM for routing MSDP for interconecting s R1&R2 Uses R1 as 94 Configuring PIM Sparse Mode ip multicast-routing E0 S0 interface Ethernet 0 ip address ip pim sparse-mode interface Serial 0 ip address ip pim sparse-mode ip pim rp-address ip pim accpt-rp ip msdp peer connect-source ethernet 0 ip msdp cache-sa-state Damn simple to configure Configure own box as Configure MSDP with ISP regional 95 Agenda IP Multicast Technology and Concepts IP Multicast Host-to-Router Protocols IP Multicast forwarding IP Multicast Routing Protocols Multiprotocol BGP Multicast source discovery protocol Source Specific Multicast Exchange points using S 96 32

33 Source Specific Multicast Simplify solution for well-known sources, particularly in cases where there is a single source sending to a given group. Allow immediate use of shortest forwarding path to a specific source, without need to create shared tree. Eliminate dependence on MSDP for finding sources. Simplify address allocation for global, single source groups when combined with elimination of shared trees (232/8). 97 PIM Source Specific Mode Source Receiver learns of source, group/port Receiver sends IGMPv3 (S,G) Join First-hop sends PIM (S,G) Join directly toward Source (S, G) Join A B D Out-of-band source directory, example: web server IGMPv3 (S, G) Join C E Receiver 98 PIM Source Specific Mode Source Result: Shortest path tree rooted at the source, with no shared tree. A B D Out-of-band source directory, example: web server C E Receiver 99 33

34 Objective of SSM Multicast Optimize multicast forwarding when sources are few and specifically known to receiver in advance of joining. Domain B Domain C r r Domain E r r S r Domain A r r Domain D S Multicast source r Multicast receiver Interdomain links Multicast traffic 100 Where Is SSM? Framework draft-holbrook-ssm-00.txt BCP proposal draft-shep txt Waiting for IGMPv3 on hosts 101 What if source is well-known? Simplify solution for well-known sources, particularly in cases where there is a single source sending to a given group. Allow immediate use of shortest forwarding path to a specific source, without need to create shared tree. Eliminate dependence on MSDP for finding sources. Simplify address allocation for global, single source groups when combined with elimination of shared trees (232/8)

35 SSM Objective Join source, Get content on shortest path Join Domain E Data Flow Domain B Domain C r r r Domain D s Domain A 103 Source Specific Multicast Allows first-hop router to respond to receiver initiated join requests for specific sources within a group. Allows first-hop router to send s,g join directly to source without creation of shared tree. Support elimination of shared tree state in 232/8, simplifying address allocation. 104 Source Specific Multicast Long term solution: IGMPv3 in routers and hosts Allows for inclusions lists and exclusion lists PIM-SSM Sends immediate PIM S,G joins based on include lists Prevents *,G joins from being sent Interim solutions: Achieve SSM functionality when IGMPv3 not yet deployed

36 IGMPv H1 H2 Report for H rtr-a 2nd S,G join(s) 1st *,G join Host sends IGMPv2 report for group DR adds membership DR sends *,G join to (it has to, it doesn t know the sources) DR sends S,G join to source (data provides the sources) 106 IGMPv H1 H2 Report for source_list H rtr-a S,G join(s) Host sends IGMPv3 report for group which can specify a list of sources to explicity include. IPMulticastListen (Socket, IF, G, INCLUDE, source-list) DR adds membership. DR sends S,G join directly to sources in the source_list, and is not required to send *,G join to (and must not in 232/8). 107 PIM Source Specific Mode Source Host learns of source, group/port First-hop learns of source, group/port First-hop send PIM s,g join directly (S, G) Join A B D Out-of-band source directory, example: web server (S, G) report C E Receiver

37 PIM Source Specific Mode Source Result: Shortest path tree rooted at the source, with no shared tree. A B D C E Receiver Effect of shared trees Can t control traffic on shared tree Can t avoid address collisions 110 Eliminating Shared Trees Source B Source C *,G Join Data Source A *,G forwarding trees Receiver 1 Want: source A, G, but can only ask for: *,G

38 Eliminating Shared Trees Source B Source C *,G Receiver 1 Source A Join Data With data arrival we know S so DR can now send S,G join. 112 Eliminating Shared Trees Source B sa-message Source C registers *,G Receiver 1 Source A Finally, shortest path but with *,G forwarding trees: Still could get packets from unintended sources: - Source B: registers - Source C: sa-messages 113 Eliminating Shared Trees Source B sa-message C Source C B registers A *,G Receiver 1 Source A How to eliminate *,G A: Don t create *,G using pim-ssm B. Filter registers C. Filter sa-messages

39 Eliminating Shared Trees Problem: Must specify what group SSM applies to globally. Solution: 232/8 has been allocated by IANA. In this range: Config PIM-SSM code, include at least 232/8: prevents *,G Config pre-pim-ssm code: filter registers for sources in 232/8 filter sa-messages for sources in 232/8 115 So where is IGMPv3? IGMPv3 - currently an IETF draft draft-ietf-idmr-igmp-v3-04.txt (NOTE: Up for last call now) Most multicast host/router vendors doing initial implementations: cisco: IGMPv3 implementation commited. Full IGMPv3 host stacks and apps are in initial implementation phase now. FreeBSD, LINUX MIM, vic/vat : What about windows apps? 116 Source Specific Multicast Interim solution: IGMPv3-lite Utilizes simple daemon so application can send v3 messages with source include info directly to router. Daemon available for win95/98/00, MacOS Interim solution: URD URL RenDezvous Requires no changes to host stack or apps. First-hop router intercepts S,G info from http redirect sent by content provider s web page

40 How to Get There What needs to be done: Deployment of PIM-SM/SSM multicast Config 232/8 filtering when PIM-SM Deployment of IGMPv3 on DR s IGMPv3 capable stacks, applications v3-lite or URD when IGMPv3 not available Source content 232/8 (source specific only), and non-232/8 Further develop web based elements 118 Agenda IP Multicast Technology and Concepts IP Multicast Host-to-Router Protocols IP Multicast forwarding IP Multicast Routing Protocols Multiprotocol BGP Multicast source discovery protocol Source Specific Multicast Exchange points using S 119 Putting it all together.. PIM-SM, MBGP, MSDP Public multicast peering (MIX) Transit topology examples Address allocation GLOP draft-ietf-mboned-static-allocation-00.txt

41 ISP Requirements at the MIX Current solution: MBGP + PIM-SM + MSDP Environment ISPs run imbgp and PIM-SM (internally) ISPs multicast peer at a public interconnect Deployment Border routers run embgp The interfaces on interconnect run PIM-SM s MSDP peering is fully meshed All peers set a common distance for embgp 121 ISP Requirements at the MIX Peering Solution: MBGP + PIM-SM +MSDP ISP A PIM-SM imbgp Public Interconnect PIM-SM imbgp ISP B imbgp embgp Redistribute old MBONE DVM routes into MBGP imbgp ISP C PIM-SM AS ISP to D-GIX CPE CPE ACCESS CORE ACCESS CORE R P CORE PEER D-GIX ISP s ACCESS R P

42 S Multicasting Support Packet flow Sourced onto ring with multicast bit set Received by appropriate routers on ring Stripped from ring by source No processing to make copies Source 124 Multicast Transit Design Objectives PIM Border Constraints Confine registers within domain Confine local groups Confine announcements Control SA advertisements via MSDP Border F check F check against unicast routes to multicast sources MSDP F check F check toward in received SAs 125 IETF Documents IDMR WG Framework draft-bhattach-pim-ssm-00.txt New SSM WG IGMPv3 PIM SSM Arch draft-ietf-idmr-igmp-v3-04.txt draft-holbrook-idmr-igmpv3-ssm-00.txt Ref API draft-ietf-idmr-msf-api-00.txt draft-ietf-pim-sm-v2-new-00.txt Combined PIM-SM/SSM PIM WG draft-holbrook-ssm-arch.00.txt 232/8 BCP draft-shep-ssm txt MBONED WG