!!!!!_5 IP Multicast in DOCSIS 3.0

IP Multicast Support in DOCSIS 3.0IP Multicast Support in DOCSIS 3.0

Greg WhiteLead Architect – Broadband AccessCableLabs

9/29/2006 © Cable Television Laboratories, Inc. 2006. All Rights Reserved. Proprietary/Confidential

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OutlineOutline

• Key New Features• Technical Overview


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Source Specific Multicast-SSMSource Specific Multicast-SSM• Feature Description

Delivery of multimedia (audio/video) services from one source tomultiple subscribers’ CPEs (IPv4 & IPv6) based on customer request

• Why was this incorporated?Previous versions did not support MSO directed multicast (any member of the multicast group could transmit)

• BenefitsEnables operators to offer broadcast-like services over DOCSIS network based on subscriber demand (e.g. IPTV service)Enables bandwidth efficient on-demand multimedia services as compared with unicastFacilitates offering of interactive video/audio and data services

• Requirements and restrictions for deploymentRequires DOCSIS 3.0 specifications compliant CMTS & 1.1 or greater CM


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QoS Support for MulticastQoS Support for Multicast• Feature Description

Provides guaranteed bandwidth for multicast sessionsProvides ability to control the amount of bandwidth that can be used by multicast traffic that is not part of an MSO service offering

• Why was this incorporated?Required to offer entertainment quality video services over DOCSIS network

• BenefitsEnables differentiation of QoS-enabled multicast servicesEnables service level guarantees to be offered to the end customerEnables offering of QoS-enabled packages to third parties

• Requirements and restrictions for deployment- Requires DOCSIS 3.0 specifications compliant CMTS & 1.1 or

greater CM- Cable operator needs to configure QoS parameters for various

multicast sessions


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PHS for MulticastPHS for Multicast

• Feature DescriptionAbility to suppress multicast packet headers

• Why was this incorporated?MSO requested addition of this feature

• BenefitsProvides bandwidth savings for bandwidth intensive multicast services such as IPTVEnables MSOs to transmit more multicast sessions for a given amount of downstream channel spectrum

• Requirements and restrictions for deployment- Requires DOCSIS 3.0 specifications compliant CMTS & 3.0

CM


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Enhanced Multicast AuthorizationEnhanced Multicast Authorization• Feature Description

Ability to provide conditional access mechanism for multicast servicesAbility to limit the number of simultaneous multicast sessions offered to a subscriberCentralized management of multicast service tiers

• Why was this incorporated?To simplify and enhance the solution specified in earlier version of DOCSIS specification

• BenefitsEnables operators to offer tiered (Gold, Silver, etc.) broadcast-like video services over DOCSIS network (e.g. IPTV)Enables offering of multicast-enabled service packages to third party service providers

• Requirements and restrictions for deployment- Requires DOCSIS 3.0 specifications compliant CMTS & 1.1

or greater CM


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Technical OverviewTechnical Overview• Removal of IGMP Snooping at the CM• DSID Labelling • CMTS initiated DSID Signalling• DSID-based filtering and forwarding by

the CM


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IGMP Snooping in 1.1/2.0 CMIGMP Snooping in 1.1/2.0 CM• DOCSIS 1.1/2.0 required the CM to snoop IGMPv2 join

messages sent by CPEs behind the CM• Establishes forwarding of multicast packets addressed

to ASM groups (G) joined by the CPEs• DOCSIS 3.0 requires support for IGMPv3 that enables

clients to join Source Specific Multicast channels• DOCSIS 3.0 also requires support for multicast traffic for

IPv6 clients that use Multicast Listener Discovery (MLD) protocol• MLDv1 to join ASM groups and MLDv2 to join SSM

channels• More than likely that future versions of DOCSIS may

require support for other future multicast protocols


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No Snooping in 3.0 CMNo Snooping in 3.0 CM• Expanding CM snooping functionality to include

aforementioned and future multicast protocols is not scalable and complicates CM implementation

• DOCSIS 3.0 removes the CM requirement to snoop IGMP join messages. The CM is required to transparently forward upstream join messages

• DOCSIS 3.0 defines a new CMTS-initiated signaling mechanism to enable forwarding of multicast packets in the CM


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DSID LabellingDSID Labelling• CMTS labels all downstream multicast packets

with a Downstream Service ID (DSID) label• DSID is 20 bit field in the Downstream Service-

Extended Header (DS-EHDR) that identifies packets belonging to an IP Multicast Session (ASM or SSM) in a MAC domain

DSID is a forwarding criterion at the CM for multicast traffic

• DSID also identifies all the packets in a “resequencing context” when downstream channel bonding is used for multicast packets


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DS EHDR FormatsDS EHDR Formats• New Extended Header (EHDR) in the DOCSIS

MAC-Layer Frame header• Three formats defined

“1-Byte” to carry Traffic Priority tag–Layer 2 priority tagging for non-bonded

unicast traffic“3-Byte” to carry Traffic Priority & DSID–DSID labeling for non-bonded multicast traffic

“5-Byte” to carry Traffic Priority, DSID & Seq. Number–DSID label & Seq. Number for bonded traffic

(multicast as well as unicast)


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DS-EHDRs for Multicast PacketsDS-EHDRs for Multicast Packets

• Type (4 bits) = 8• Length (4 bits) = 6• P (3 bits) = Traffic Priority• X (1 bit) = Reserved (unused)• S (1 bit) = Sequence Change Count

Toggled by CMTS whenever Sequence Number is reset to zero• DSID (20 bits) = Downstream Service ID (Identifies an IP Multicast Session)• Sequence Number (16 bits) = Resequencing Context for bonded multicast

packets

T = 8

L = 5 P S DSID (20 bits) Sequence Number

(16 bits)

“5-Byte” DS EHDR for bonded multicast packet

T = 8

L = 5 P X DSID (20 bits)

“3-Byte” DS EHDR for non-bonded multicast packet


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CMTS-initiated DSID SignalingCMTS-initiated DSID Signaling• CMTS communicates DSIDs to the CM via:

MAC Domain Descriptor (MDD)– For Pre-Registration IPv6 multicast traffic

Registration Response (REG-RSP)– For unicast bonded traffic and static multicast

Dynamic Bonding Change Request (DBC-REQ)– For “joined” multicast sessions

• In REG-RSP and DBC-REQ, the CMTS communicates group forwarding attributes associated with DSID

MAC addresses of clients that joined the IP Multicast Session Cable Modem Interface Mask (CMIM) for statically joined clients such as eSAFE devices (e.g. eSTB, ePS)


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DSID Forwarding at CMDSID Forwarding at CM• DSID is a CM filtering & forwarding criterion• CM discards packets labelled with unknown

DSIDs• CM forwards Multicast Packets labelled with the

DSID to a set of interfaces identified by the union of:

A set of interfaces derived from a list of client MAC addresses associated with a DSID, and;A set of interfaces identified in the Multicast CMIM associated with the DSID


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Thank You!Thank You!

CableLabs

Greg C. WhiteLead ArchitectBroadband Access

Cable Television Laboratories, Inc.858 Coal Creek Circle

Louisville, Colorado 80027-1266Phone: 303-661-9100Direct: 303-661-3822

Fax: 303-664-8192Email: [email protected]

http://www.cablelabs.com

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!!!!!_5 IP Multicast in DOCSIS 3.0