IPv6 multicast-tm-v5

© 2012 Cisco and/or its affiliates. All rights reserved. 1

“Tech Session” IPv6 Multicast Primer

Tim Martin

CCIE #2020

Solutions Architect

Fall 2013


•  Link Operations •  Routing Protocols •  Distance Learning •  Surveillance •  Metering •  Broadcast Video Services •  Efficient Delivery


•  Mechanism for transmitting information from a single source (root) to many receivers (leaves)

•  Single copy of a datagram is sent from the source and replicated through the tree to receivers

•  No restriction on physical or geographical boundary

Source D

own

the

tree

Single copy of datagram

Replication

Receivers Receivers


IPv6 Address Family

Multicast Anycast Unicast

Assigned Solicited Node

Unique Local Link Local Global Special Embedded

*IPv6 does not use broadcast addressing



•  IPv6 has a specific Ethernet Protocol ID •  IPv6 relies heavily on Multicast

Destination Ethernet Address!

Source Ethernet Address!

0x0800!!

IPv4 Header and Payload!

Destination Ethernet Address!

Source Ethernet Address!

0x86DD!!

IPv6 Header and Payload!

xx 33 33 xx xx xx

I bit = Local Admin, L bit = Multicast/Broadcast

0000 00IL


•  IPv6 multicast address to Ethernet mapping

•  Destination address based mechanism

FF02:0000:0000:0000:0000:0001:FF17:FC0F IPv6 Multicast Address

Corresponding Ethernet Address 33 33 17 FC 0F FF

Low order 32 bits

IPv6 Ethernet Frame Multicast Prefix



Node A can start using address A

B A C

•  Probe neighbors to verify address uniqueness

ICMP Type 135 NS IPv6 Source UNSPEC = ::

IPv6 Dest. A Solicited Node Multicast FF02::1:FF00:A

Data FE80::A Query Anyone using A?

NS


•  For each Unicast and Anycast address configured there is a corresponding solicited-node multicast

•  Multicast for resolution, Unicast for reachability

•  Solicited-node multicast consists of FF02::1:FF/104 {lower 24 bits from IPv6 Unicast interface ID}

FF02 0000 0000 0000 0000 0001 FF17 FC0F

2001 0DB8 1234 0001 0200 CAFF FE17 FC0F


R1#sh ipv6 int e0 Ethernet0 is up, line protocol is up

IPv6 is enabled, link-local address is FE80::200:CFF:FE3A:8B18 Global unicast address(es):

2001:DB8:0:1234::1 subnet is 2001:DB8:0:1234::/64 Joined group address(es): FF02::1 FF02::2 FF02::1:FF00:1 FF02::1:FF3A:8B18 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds ND advertised reachable time is 0 milliseconds ND advertised retransmit interval is 0 milliseconds ND router advertisements are sent every 200 seconds *If EUI format is used then the 1rst solicited node mcast addr is used for both the LL & GU

Solicited-Node Multicast Address*


A! B!

ICMP Type 135 NS IPv6 Source FE80::A

IPv6 Destination B Solicited Node Multicast FF02::1:FF00:B

Target Address 2001:db8:1:46::B Code 0 (need link layer) Query What is B link layer

address?

ICMP Type 136 NA IPv6 Source FE80::B

IPv6 Destination FE80::A Target Type 2

Data Link Layer address of B *Flags R = Router

S = Response to Solicitation O = Override cache information

NS NA

•  Local Link only, Not Routed

•  ARP replacement, Map’s L3 to L2.

•  Multicast for resolution, Unicast for reachability



•  Multicast is a normal IPv6 packet Destination

•  An IPv6 multicast group address always starts with the prefix FF00::/8 (1111 1111)

•  Multicast Listener Discovery (MLD)

•  Multicast traffic is forwarded along a multicast tree which can be either a Source Tree (S, G) Shared Tree (*, G)

•  IPv6 supports Protocol Independent Multicast (PIM) routing protocols only PIM creates the trees that multicast streams are forwarded on

PIM operation is the same in IPv6 as IPv4 (RFC 4601 specifies operation over IPv4 and IPv6) PIM identified by the IPv6 next header 103 (same protocol type as IPv4)

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•  General Any Source Multicast (ASM) PIM-SM, PIM-BiDir Default for generic multicast and unicast prefix-based multicast Start with FF3x::/12

•  Source Specific Multicast (SSM) Used by PIM-SSM FF3x::/32 is allocated for SSM by IANA However, at present prefix and plen must be zero so FF3x::/96 is usable as SSM

•  Embedded RP groups PIM-SM, PIM-BiDir Start with FF70::/12


•  Prefix FF00::/8 8-bit 4-bit 4-bit 112-bit

1111 1111 0 R P T Scope Variable format

Flags

O Reserved

R = 0 R = 1

No embedded RP Embedded RP

P = 0 P = 1

Without Prefix Address based on Prefix

T = 0 T = 1

Well Known Address (IANA assigned) Temporary address (local assigned)

Scope 1 Node

2 Link

3 Subnet

4 Admin

5 Site

8 Organization

E Global


•  Every Unicast prefix can build custom multicast addresses

•  Last 32 bits of unicast address mapped into Group ID (112 Bits) 8 Bits 4 Bits 4 Bits 8 Bits 8 Bits 64 Bits 32 Bits

1111 1111 0 0 1 1 1110 Rsvd plen Unicast Prefix Group ID

Example plen 40 = 64 bits

Prefix 2001:db8:cafe:1::

Group ID 11d7:4cd3

FF3E:0040:2001:DB8:CAFE:1:11D7:4CD3


•  Special case of unicast prefix-based address Based on Unicast based multicast format

•  Prefix Len=0, Network Prefix=0

•  FF3x::/32 pool is reserved for SSM addresses FF3x::/96 initial block allocated from this pool

Example Unicast Prefix 0::

Flags No RP, Unicast, Temporary

Scope 8 (Organisation)

Group ID 8000:247

ff38::8000:247

32 Bits 8 Bits 4 Bits

0011 Group ID 1111 1111 1000

4 Bits

Network Prefix=0 Plen=0

64 Bits 8 Bits

Rsvd

8 Bits

Tem

porary (T)

Unicast B

ased (P)

Range Usage

FF3x::4000:0001 - FF3x::7FFF:FFFF IANA allocation

FF3x::8000:0000 - FF3x::FFFF:FFFF Dynamic allocation

FF3x::0000:0000 - FF3x::3FFF:FFFF Invalid for IPv6 SSM


•  Static mapping of RP into Multicast group

•  Solves MSDP and scaling issues 8 Bits 4 Bits 4 Bits 4 Bits 4 Bits 8 Bits 64 Bits 32 Bits

1111 1111 0 1 1 1 1110 Rsvd RPid plen Unicast Prefix Group ID

Example Rsvd/RPid 0000 | 0101

Prefix 2001:db8:cafe:1::

Group ID 645

FF7E:0540:2001:DB8:CAFE:1:0000:0645

FF7E:540:2001:db8:cafe:1::645

2001:db8:cafe:1::5


Address Scope Meaning FF01::1 Node-Local This Node

FF05::2 Site-Local All Routers

FF02::1 Link-Local All Nodes

FF02::2 Link-Local All Routers

FF02::5 Link-Local OSPFv3 Routers

FF02::6 Link-Local OSPFv3 DR Routers

FF02::9 Link-Local RIPng

  FF02, is a permanent address and has link scope

  Link Operations, Routing Protocols, Streaming Services



Type Code Data

Checksum

•  Neighbor Discovery, Router Discovery, Path MTU Discovery and (MLD) Type – (1-127) = Error Messages, (128-255) = Informational Messages Code – More Granularity within the Type Checksum – computed over the entire ICMPv6 Data - Original Header Return (8 bytes), then fill to Min MTU (1280)

58

IPv6 basic header

ICMPv6 Header

Next Header *58, not 1 (ICMP)


•  MLD uses LL source addresses

•  3 msg types: Query, Report, Done

•  MLD packets use “Router Alert” in HBH

•  MLDv1 = (*,G) shared, MLDv2 = (S,G) source

MLD snooping

MLD IGMP Message Type

ICMPv6 Type Function

MLDv1 (RFC2710) IGMPv2 (RFC 2236) Listener Query

Listener Report

Listener Done

130

131

132

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

130

143

Used to find out if there are any multicast listeners

Enhanced reporting, multiple groups and sources


•  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 Type 131

IPv6 Source fe80::209:5bff:fe08:a674

IPv6 Destination FF38::276

Hop Limit 1

Group Address ff38::276

Hop-by-Hop Header

Router Alert Yes

MLD Report

A MLD Report

B I wish to receive

ff38::276 I wish to receive

ff38::276

MLD Report (B)

ICMP Type 131

IPv6 Source fe80::250:8bff:fE55:78de


Hop Limit 1


Hop-by-Hop Header

Router Alert Yes

(S, G)

Source for multicast ff38::276

fe80::209:5bff:fe08:a674 fe80::250:8bff:fE55:78de fe80::207:85ff:fe80:692


MLD Done (A)

ICMP Type 132


IPv6 Destination FF02::2 (All routers)

Hop Limit 1


Hop-by-Hop Header

Router Alert Yes

MLD Done (A)

A

fe80::209:5bff:fe08:a674 MLD Report (B)

B

fe80::250:8bff:fE55:78de

I wish to leave ff38::276

I am watching ff38::276

MLD Query (C)

ICMP Type 130

IPv6 Source fe80::207:85ff:fe80:692


Hop Limit 1

Hop-by-Hop Header

Router Alert Yes Q

uery (C)

fe80::207:85ff:fe80:692

C MLD Report (B)

ICMP Type 131

IPv6 Source fe80::250:8bff:fE55:78de


Hop Limit 1


Hop-by-Hop Header

Router Alert Yes


MLD Report (A)

ICMP Type 143



Hop Limit 1

# of Records Include/exclude

Group Address FF38::4000:BA11

Hop-by-Hop Header

Router Alert Yes

MLD Report

A I wish to receive FF38:4000:BA11

(S, G)

Source for multicast FF38::4000:BA11

fe80::209:5bff:fe08:a674


•  General Query FF02::1

Group list empty, who’s listening?

•  Group Specific Query FF38::4000:BA11

Anyone still interested in this stream?

•  Group & Source Specific Query 2001:DB8:CAFÉ::1, FF38::4000:BA11

•  Filter Mode, Change Record

•  Multiple routers on link Lowest address value assumes Querier role

A

Query

Source for multicast FF38::4000:BA11



•  Provides the forwarding entries for packet distribution down a tree

•  Consists of the Source Address (S) and the Destination Group (G) of the multicast stream

•  Expressed as (S, G) for Source Trees Means an explicit source for a multicast group More Memory, Optimal Paths, Less Delay

•  Expressed as (*, G) for Shared Trees Means ALL sources for a multicast group Less Memory, Sub Optimal paths, Extra Delay

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•  PIM is Join and Prune or PULL mode protocol, and transparent to the IP version It is the only multicast protocol supported for IPv6 and uses next header type 103

•  PIM Sparse-Mode (PIM-SM) - RP is required Sparse-Mode for many-to-many applications (Multiple sources, single group) Uses shared tree initially but may switch to source tree

•  Bi-directional PIM (PIM-BiDir) - RP is required Bi-Directional many-to-many (hosts can be sources and receivers) Like PIM-SM but uses a BiDIR shared tree for all traffic

•  PIM Source-Specific Multicast (PIM-SSM) - No RP is required For one-to-many applications (Single source, single group) Always uses a (S, G) source tree – (S) is learned or known from an out of band mechanism

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•  Root is a common point Rendezvous Point Many multicast groups at RP

•  Receivers join RP To learn of sources

•  Sources only transmit to RP RP forward to receivers

•  Forwarding represented as (*, G)

•  Less state required At expense of optimal routing

•  Service model is ASM

Source 2001:db8:1::20 transmitting to

group ff38::8000:247!

(*, G) entries (*, ff38::8000:247) (*, ff38::8000:212)

Receiver for ff38::8000:247

Receiver for ff38::8000:212!

Source 2001:db8:2::35 transmitting togroup ff38::8000:212!

Rendezvous Point!


•  Simplest form of tree Receiver requires knowledge of source

•  Traffic from source (root) to receivers (leaves)

•  Shortest path taken

•  Packets replicated at branch point

•  Forwarding entry states represented as (S, G)

•  Provides Optimal routing At the expense of more state (S, G)

•  Service model is SSM or ASM that has moved to an SPT

(S, G) entry is (2001:db8::1,ff38::8000:247)


Source 2001:db8::1 Group ff38::800:247



•  Traffic can travel in both directions Up and Down the tree

•  Source packets do not necessarily have to travel via the RP

•  Forwarding entries represented as (*, G)

•  Offers improved routing optimality than uni-directional shared tree

•  Service model is ASM

(*, G) entry (*, ff38::8000:247)!

Receiver B for ff38::8000:247

Receiver A for ff38::8000:247

Source 2001:db8:1::20 transmitting togroup ff38::8000:247

Rendezvous Point!


•  Multicast forwarding is the opposite of Unicast forwarding Unicast is concerned about where the packet is going Multicast is concerned about where the packet came from

•  Multicast uses Reverse-Path Forwarding (RPF) Checks if arriving packet is on reverse path back to source If successful, packets is forwarded, otherwise dropped

•  RPF procedure for PIM uses unicast routing table to find source

IPv6 Intranet √

IPv6 Intranet/Internet


Packet has arrived on wrong Interface Discard the packet!

E0 S1

S0

S2

Multicast packet from source 2001:db8:face::1

Unicast Route Table Network Interface 2001:db8:face::/48 S1

2001:db8:beef::/48 S0

2001:db8:f00d::/48 E0


Packet arrived on correct interface! Forward via all outgoing interfaces (i.e. down the distribution tree)

E0

S1

S0

S2

Multicast Packet from Source 2001:db8:face::1

Unicast Route Table Network Interface 2001:db8:face::/48 S1

2001:db8:beef::/48 S0

2001:db8:f00d::/48 E0



•  PIM-SSM and PIM-BiDir require a method to discover RPs and their related groups

•  Static RP assignment Provides static group-to-RP mapping Works the same as IPv4 configuration Bidirectional PIM (Bidir) can also use static RP assignment Anycast for redundancy

•  Embedded-RP Special case of unicast prefix-based addresses starting with FF70::/12 RP and associated group address embedded in IPv6 multicast address Single RP address only can be mapped to a group, no PIM BiDir support Some form of redundancy can be provided via Anycast technique

•  Boot-Strap Router (BSR) Provides automated group-to-RP mapping and RP redundancy


•  BSR is a non-proprietary mechanism for a router to learn RP information. Ensure routers in the PIM domain have the same RP cache as the BSR Information regarding several RPs for different groups is automatically communicated to all routers

•  Elected BSR receives candidate-RP messages from all candidate-RPs BSR advertises information about all the candidate-RPs. Each router uses a common algorithm to select the same RP address for a given multicast group.

•  Can be used with third-party routers (which support the BSR mechanism). •  There is no configuration necessary on every router separately (except on

candidate-BSRs and candidate-RPs). •  Robust mechanism permits back-up RPs to be configured.

Secondary RP for the group can take over as the RP for the group in the event of failure


•  ASM Model always requires an RP PIM-SM and Bidir-PIM must have RP

•  RP is single point of failure and redundancy is a basic operational requirement

BSR is today the only available RP redundancy solution for IPv6 (poor convergence, protocol complexity) Static-RP and Embedded RP do not have redundancy

•  Anycast-RP solution for IPv6 can help provide redundancy


•  Designate a primary and a secondary (tertiary, etc.. are possible too) RP for the anycast group.

•  Configure Primary RP with longest subnet mask on the loopback, secondary has shorter mask

•  Distribute loopback interfaces routes into IGP

Primary RP

DR 1 DR 2

Secondary RP

Loopback 1 2001:db8:fab0::1/48

Loopback 1 2001:db8:fab0::1/47



Personal Computer Operating Systems •  Windows •  Mac OS X •  Linux

Appliances & Networking •  Printers •  Access Points •  Switches •  Routers

Mobile Devices •  Smartphones •  Tablets •  Android / iOS based

AV Equipment •  Speakers •  Cameras •  Displays •  AV Receivers

Software •  Applications •  Network Management Software

Zeroconf - enables communications of hosts and services on a network that may not contain configuration services such as DNS and DHCP


•  BYOD: Massive influx of consumer devices to be placed on Enterprise networks

•  Consumer devices are typically located within a single Layer 2 domain in the home

•  Users may expect to have the same type of services in the Enterprise / Campus but also across L3 boundaries

•  Device types include mobile devices (iOS, Android), printers, cameras, PCs etc.


Same L2 Domain

Where’s my

Printer?

Different L2 Domain (other subnet)

I’m here! Talk to me...


Same L2 Domain

Where’s my

Printer?

Different L2 Domain (other subnet)

Nobody's talking to

me!?

Service Browsing


•  Service Naming and Service Discovery

•  Apple = Bonjour, Windows = Rally

•  FF02::FB – mDNS – Multicast DNS •  FF02::C – SSDP – Simple Service Discovery Protocol

FF02::C – UPnP – Universal Plug and Play

•  FF02::1:3 – LLMNR – Link Local Multicast Name Resolution •  Apple has a light weight approach, adopted quicker

•  Microsoft has a more robust, heavier implementation and has moved slower


•  Service Discovery Is your Phone Book. Tell me, where I can reach Mr. Printer Doesn’t necessarily mean that you can actually reach / talk to Mr. Printer

•  Access Control Is like caller screening Even if a person is not listed in the phone book, you might call that person because you know the number “I know Mr. Printer is at 1.2.3.4, let’s call him even if I don’t see him in the phone book”

•  Better Together use the phone book for easy lookup (Service Discovery) use the caller screening for security (ACL / SGT / SGACL ...)


VLAN 200 VLAN 100

CAPWAP

Advertisement

•  Link Local Multicast seen in SAME VLAN only

•  Cached at Gateway

•  Instance Name, Type, Interface Name, TTL, Resource Record data etc.

enabled

Training ATV RAOP Service VLAN 100 CTO Office IPP Service VLAN 200 Instance name Other VLAN XYZ

RAOP! IPP!


VLAN 200 VLAN 100

CAPWAP

Query

•  Service query seen and answered by Gateway

•  Original Device not bothered

•  Cache maintenance done on TTL / when device goes offline

enabled

Training ATV RAOP Service VLAN 100 CTO Office IPP Service VLAN 200 Instance name Other VLAN XYZ

IPP?

IPP!

RAOP?

RAOP!


VLAN 200 VLAN 100

CAPWAP

Cache Entry removed when •  Device disappears when

TTL expired •  Service is explicitly

removed by Device

enabled

Training ATV RAOP Service VLAN 100 Instance name Other Services

VLAN XYZ CTO Office IPP Service VLAN 200 Instance name Other VLAN XYZ



•  Applications We Haven't Even Built Yet

•  Large Privately Owned Multicast Address Space

•  Built-in Scoping

•  No NAT required

•  Embedded RP, Anycast, Etc..

•  Multicast is Foundational in IPv6

•  Invest in your future - IPv6, the future is now

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Technology

IPv6 multicast-tm-v5