IPv6 Multicast 6DEPLOY. IPv6 Deployment and Support

Intro Multicast is inherent to the IPv6 protocol No broadcasts Multicast used instead But some parts need to be configured for building the multicast trees for topology information (routing)

Agenda Multicast addressing MLD & MLDv2 PIM SM/SSM Interdomain multicast

Multicast addressing (1) Multicast addresses format: (RFC 3513) 8 high order bits set to 1  Addresses derived from FF00::/8 prefix flag field(4 bits) : 0RPT values  T = 0 for permanent addresses (Defined by IANA)  T = 1 for transient addresses  Bits P and R discussed later scope field  Makes it possible to limit the scope of the multicasting  0 - Reserved4 - Admin-local  1 – Node-local5 - Site-local  2 – Link-local8 - Organization-local  3 – Subnet-localE - Global (Internet) 8 bits4 bits 112 bits 1111 flagsscopegroup ID FF

Multicast addressing (2) Scopes must be configured on routers! Examples of IANA allocated addresses Flag bits T=P=R=0  Flag = 0 Group ID 101  NTP servers  FF01:0:0:0:0:0:0:101 : All the NTP servers on the sender’s host  FF02:0:0:0:0:0:0:101 : All the NTP servers on the sender’s link  FF05:0:0:0:0:0:0:101 : All the NTP servers on the sender’s site  FF0E:0:0:0:0:0:0:101 : All the NTP servers on the Internet

AddressScopeMeaning FF01::1Node-LocalAll Nodes FF01::2Node-LocalAll Routers FF02::1Link-LocalAll Nodes FF02::2Link-LocalAll Routers FF02::5Link-LocalOSPFv3 Routers FF02::6Link-LocalOSPFv3 DR Routers FF02::1:FFXX:XXXXLink-LocalSolicited-Node Well Known Multicast Addresses  “02” means that this is a permanent address (t = 0) and has link scope (2)  RFC 2375

Multicast Mapping over Ethernet (RFC 2464) FF02:0000:0000:0000:0000:0001:FF17:FC0F IPv6 Multicast Address Corresponding Ethernet Address IPv6 Ethernet Frame Multicast Prefix 33 17FC0FFF Low order 32 bits Requires 8th bit of MAC address to be set to 1 For IPv6 = xx-yy-zz-kk xx-yy-zz-kk are 32 lower bits of the IPv6 address Example: = FF3E:40:2001:660:3007:123:1234:5678 =

32 bits 24 bits Solicited Node Multicast Address Example 64 Bits Interface ID 64 Bits Network ID 00003A8B FF0000 FF B180CFF0000 FE80FE3A Link-Local Solicited Node Multicast B3AFF Ethernet Multicast Multicast address built from unicast address Concatenation of FF02::1:FF00:0/ low order bits of the unicast address Nodes build their own IPv6 solicited node multicast address Nodes that know the IPv6 address of a host but not its MAC address can use the solicited node multicast address NDP protocol (Neighbor Discovery Protocol) Protocol for DAD management Avoids sending MAC broadcasts (FF-FF-FF-FF-FF-FF)

cat6500-1>sh ipv6 int vlan 200 Vlan200 is up, line protocol is up IPv6 is enabled, link-local address is FE80::2D0:D3FF:FE81:9000 Description: --- To cat Global unicast address(es): :DB8:12::1, subnet is 2001:DB8:12::/64 Joined group address(es): FF02::1 FF02::2 FF02::5 FF02::D FF02::16 FF02::1:FF00:1 FF02::1:FF81:9000 cat6500-1>sh ipv6 int vlan 200 Vlan200 is up, line protocol is up IPv6 is enabled, link-local address is FE80::2D0:D3FF:FE81:9000 Description: --- To cat Global unicast address(es): :DB8:12::1, subnet is 2001:DB8:12::/64 Joined group address(es): FF02::1 FF02::2 FF02::5 FF02::D FF02::16 FF02::1:FF00:1 FF02::1:FF81:9000 All nodes All routers OSPF Routers All PIM Routers Global Link-Local IPv6 Addresses – Unicast and Multicast Examples All MLDv2 capable Routers Solicited node multicast (for link-local) Solicited node multicast (for global)

Multicast addresses derived from unicast prefixes Described in RFC 3306 Flag : 0RPT Flags : 0RPT  P=0  Address not based on the unicast prefix  P=1  Address based on the unicast prefix  If P=1  T=1  FF30::/12 prefix –(T=1 because not allocated by IANA) Reserved : 0 Example:prefix 2001:660::/32 (RENATER) address FF3E:20:2001:660:0:0:1234:abcd flags scope reservedPrefix Length Network prefix Group ID 8 bits bits 8 64 bits32 bits

SSM addresses Are also RFC3306 addresses SSM addresses range: FF3X::/32 Only addresses in FF3X::/96 should be used now. These are RFC3306 addresses with: P = 1 Plen = 0 Prefix = 0 Example: FF3x::1234:abcd / :abcd being the Group ID

Multicast addresses allocation « Manual » choice of multicast address and port Dynamic Session Announcement Protocol, (SAP), ID  SDR implements SAP (not scalable for a global scope) MADCAP, RFC 2730  Multicast Address Dynamic Client Allocation Protocol (too much complex, very few implementations and no deployment) GLOP, RFC 2770  Useless as we have RFC 3306 Multicast addresses derived from unicast prefixes (RFC 3306) Any host can derive a multicast address from the network prefix where it is connected Makes allocation easier How to assign addresses to end user remains a problem

Agenda Multicast addressing MLD & MLDv2 PIM SM/SSM Interdomain multicast

Multicast Listener Discovery MLD manages multicast interaction Between listeners and their routers (Joins, Leaves) MLD is equivalent to IGMP in IPv4 MLD is a sub-protocol of ICMPv6 Switches have MLD snooping MLDv1 (RFC 2710) MLD IGMPv2 ASM only MLDv2 (RFC 3810) MLDv2 IGMPv3 SSM + AS Host Multicast Control via MLD messages Router Switch Receivers MLD snooping

MLD Versions There are two versions of MLD that map to IGMP versions MLDv1 allows joining to a particular group (any available source) (*, G) MLDv2 allows joining to a particular group and a specific source (S, G) MLDv2 backwards compatible with MLDv1 (supports 131 and 132 message types) MLDIGMP Message Type ICMPv 6 Type Function MLDv1 (RFC2710)IGMPv2 (RFC 2236) Listener Query Listener Report Listener Done Used to find out if there are any multicast listeners Response to a query, joins a group Sent by node to report it has stopped listening MLDv2 (RFC 3810)IGMPv3 (RFC 3376)Listener Query Listener Report Used to find out if there are any multicast listeners Enhanced reporting, multiple groups and sources

MLD Packet MLD message Message type: ICMPv6 IPv6 Header next header = 0 (Hop-by-hop) Hop-by-hop extension Option = Router alert Next header = 58 (ICMPv6) MLD is a sub-protocol of ICMPv6 MLD uses link local source addresses Uses “Router Alert” in extension header (RFC2711) Forces routers to look at message

MLDv1 Message Type : Messages types –General Query and Multicast-Address-Specific Query (130) –Multicast Listener Report (131) –Multicast Listener Done (132) Code : Set to 0 by sender and ignored then Checksum : for the complete packet (headers+MLD message) Maximum Response Delay : For query messages, time by which hosts must respond Reserved : Not used: set to 0 and ignored then Multicast Address: IPv6 multicast address or 0 according to message type

MLDv1 Example Joining a Group (REPORT) Hosts send MLD report to alert router they wish to join a multicast group Router then joins the tree to the source or RP MLD Report (A) ICMP Type131 IPv6 Sourcefe80::209:5bff:fe08:a674 IPv6 Destinationff38::276 Hop Limit1 Hop-by-Hop Header Router AlertYes MLD Report 1 A 2 B I wish to receive ff38::276 I wish to receive ff38::276 MLD Report (B) ICMP Type131 IPv6 Sourcefe80::250:8bff:fE55:78de IPv6 Destination ff38::276 Hop Limit1 Hop-by-Hop Header Router AlertYes (S, G) 3 Source for multicast ff38::276 fe80::209:5bff:fe08:a674 fe80::250:8bff:fE55:78de fe80::207:85ff:fe80:692

MLDv1 Example Leaving a Group (Query) MLD Done (A) ICMP Type132 IPv6 Sourcefe80::209:5bff:fe08:a674 IPv6 Destinationff02::2 (All routers) Hop Limit1 Group Addressff38::276 Hop-by-Hop Header Router AlertYes MLD Done (A) 1 A fe80::209:5bff:fe08:a674 MLD Report (B) 3 B fe80::250:8bff:fE55:78de I wish to leave ff38::276 I am watching ff38::276 MLD Query (C) ICMP Type130 IPv6 Sourcefe80::207:85ff:fe80:692 IPv6 Destination ff38::276 Hop Limit1 Hop-by-Hop Header Router AlertYes Query (C) 2 fe80::207:85ff:fe80:692 C MLD Report (B) ICMP Type131 IPv6 Sourcefe80::250:8bff:fE55:78de IPv6 Destination ff38::276 Hop Limit1 Hop-by-Hop Header Router AlertYes

MLDv2 (RFC 3810) Management of group & sources INCLUDE : to receive packets from sources specified in the MLDv2 message EXCLUDE : to receive packets from all sources except the ones specified in the MLDv2 message 2 types of messages Multicast listener query messages Multicast listener report messages Interoperable with MLDv1

Further MLD Information Leave/DONE Last host leaves - Sends DONE (Type 132) Router will respond with Group-Specific Query (Type 130) Router will use the Last member query response interval (Default=1 sec) for each query Query is sent twice and if no reports occur then entry is removed (2 seconds) General Query (Type 130) Sent to learn of listeners on the attached link Sets the Multicast Address Field to zero Sent every 125 seconds (configurable)

Agenda Multicast addressing MLD & MLDv2 PIM SM/SSM Interdomain multicast

PIM SM/SSM Protocol Independant Multicast No basic difference with PIM for IPv4 Except PIM messages are sent with link-local IPv6 address Except Embedded RP Creates multicast trees between senders and receivers (distribution trees) Not a routing protocol Relies on other routing protocols (MBGP, static…)

Embedded-RP (RFC 3956) Provides a static RP to multicast group mapping Flag : 0RPT R=1  Embedded-RP address If R=1  P=1  T=1 FF7x::/16 addresses Res : 0 Rpid : last 4 bits of the RP address (15 RPs per scope per prefix) E.g. RP address 2001:660:3001:104::8 Multicast Group FF7E:0840:2001:660:3001:104:1234:abcd flag scop res Prefix Length Network prefix Group ID 8 bits bits32 bits rpid 2^32 groups per RP

Agenda Multicast addressing MLD & MLDv2 PIM SM/SSM Interdomain multicast

Interdomain multicast (1) No problem for SSM. Source specific trees created from senders to receivers accross domains ASM problem: was solved in the IPv4 world with MSDP (Multicast Source Discovery Protocol) ISP AISP B MSDP RP

Interdomain multicast (2) No one wants MSDP for IPv6, not manageable/scalable SSM IETF lobby Some SSM applications already available Embedded-RP – RFC 3956 For each group, everyone uses the same RP Embedded is a solution for group-to-RP mapping Requires support in all PIM routers (that are part of the tree)

IPv4 and IPv6 Multicast Comparison ServiceIPv4 SolutionIPv6 Solution Addressing Range32-bit, Class D128-bit (112-bit Group) Routing Protocol Independent, All IGPs and MBGP Protocol Independent, All IGPs and MBGP with v6 mcast SAFI Forwarding PIM-DM, PIM-SM, PIM-SSM, PIM-bidir, PIM- BSR PIM-SM, PIM-SSM, PIM-bidir, PIM-BSR Group ManagementIGMPv1, v2, v3MLDv1, v2 Domain ControlBoundary, BorderScope Identifier Interdomain Solutions MSDP across Independent PIM Domains Single RP within Globally Shared Domains RP LearningStatic RP, BSR, Auto-RP Static RP, BSR, Auto-RP, Embedded RP

IPv6 multicast RP