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Tutorial: IP Multicast and Multipoint Design for IPTV Services
October 12, 2008 | By Cisco
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Cisco에서 작성한 IPTV 서비스를 위한 IP Multicast 관련 자료입니다. 차례는 다음과 같습니다. 1. Introduction 2. Architectural overview 3. IP multicast primer (SSM) 4. Transit Transport Design options     Native (PIM), mLDP, RSVP-TE P2MP, L2/L3VPN, signaling 5. Resiliency     Source redundancy, protected pseudowires, FRR, live-live, MoFRR 6. Broadband Edge     IGMP snooping, MVR, vVLAN, DSL, Cable, FTTH 7. Path selection     ECMP, multi topologies, RSVP-TE P2MP 8. Admission control 9. Channel changing     Join/leave latency, static/dynamic forwarding, acceleration

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Transcript
Mike McBride

Session Goal

To provide you with a thorough understanding of the end-to-end protocol, mechanics and service element of IP multicast technologies used in IPTV networks.
ⓒ 2008 Cisco Systems, Inc. All rights reserved.

Agenda
. Introduction . Architectural overview . IP multicast primer (SSM) . Transit Transport Design options
Native (PIM), mLDP, RSVP-TE P2MP, L2/L3VPN, signaling . Resiliency Source redundancy, protected pseudowires, FRR, live-live, MoFRR . Broadband Edge IGMP snooping, MVR, vVLAN, DSL, Cable, FTTH . Path selection
ECMP, multi topologies, RSVP-TE P2MP . Admission control . Channel changing
Join/leave latency, static/dynamic forwarding, acceleration

Multicast for IPTV Delivery



8 6 4 2 0

IP Multicast Is a Green Technology!!!!!!!!


Internet Protocol (IP) multicast is a bandwidth-conserving technology that reduces traffic by simultaneously delivering a
single stream of information to thousands of corporate recipients and homes; applications that take advantage of multicast include

and distribution of software, stock quotes, and news






Broadcast IPTV = IP multicast

. …however transport network transits packets ..
“Native IP multicast”, MPLS, L2, optical . IP multicast sources:
Encoder, Transcoder, Groomer, Ad-Splicer, … . IP multicast receivers:
Transcoder, Groomer, Ad-Splicer, QAM, STB
. IP == IPv6 (Japan) or IPv4 (RotW rest of the world)
No address exhaustion issue (SSM)
No/slow move to IPv6 for IPTV in RotW
Deployment strategyOverview, Recommendation
. Network
Add IP multicast to your network core Choose transport methods based on SLA and operational requirements/preferences Native IP multicast, MPLS, L2, mix Solution should minimize involvement in provisioning of individual applications/services
. IPTV services
Start with traditional broadcast TV Investigate extending IPTV and other (IP multicast) services More RoI on network layer investment
Additional service opportunities
Across common SSM IP multicast service
. No need to change the IP multicast functionality in the network
May want improvements on optional elements (RSVP, …)
. Extending IPTV broadcast service Dynamic redundancy (regional to national) Variety of reach of transmission (src->rcvr) Groomer/transcoders, Add-Splicers Switched Digital Video, oversubscription Wholesale, dynamic, international channels
. Other services Commercial (MVPN) Content pre-provisioning to VoD server, STB Multicast in Internet Service (eg: To PC) Voice conferencing, gaming, surveillance, …

50,000 feet architecture IPTV and multicast

50,000 feet architecture Goals

. Separate “network” and “services” plane
Network = shared infrastructure for all services
Routers, switches, optical gear, NMS, …
IPTV = encoders, groomers, splicers, VoD server, STB, …
Often operated by different entity/group than network

. IP multicast
Allow to attach solution plane devices (sourcing, receiving) anywhere . global, national, regional, local. Start/stop sending traffic dynamically, best utilize bandwidth only when needed.
One network technology usable for all services (IPTV, MVPN, …)
Enable network operator not to provision/worry about individualprogramming.
. Service Interface
How network & service operator infrastructure interacts with each other SLA of IP multicast traffic sent/received Signaling used
Service Interface

Basic service description (recommended IP multicast for IPTV)
. P2MP = SSM tree (traffic forwarding)
Build trees from any individual source. Easy to: Inject everywhere, receive everywhere (securely) Best join/prune latencies
Warning: fast network join is not same as fast solution join! Largest #trees supported,… No coordination of tree addresses (SSM channels) No spoofing of traffic across the tree
. Redundancy
Source redundancy: Anycast/Prioritycast
Optional live-live service (path separation)
(for up to 0 packet loss during network failure)

Service Interface More features
. Admission control
Per-flow bandwidth based admission control
RSVP-TE, RSVP/UPnP-CAC at edge
Router local admission control

. More …:
(per subscriber) access control (eg: lineup), provisioning of
subscriber policies, …
Accounting (Radius, Netflow, …)
Management, troubleshooting

Not further covered in this presentation
Lots of product specifics

Service Interface Expectation against service devices
. Mandatory:
SSM-tree building: IGMPv3/MLDv2 with SSM ‘joins’ receivers needs to know (S,G) channels to join Send multicast packets with TTL > 1    
. Optional:
DSCP setting Signaling for source redundancy Send/receive traffic twice (redundancy and/or live-live) RSVP/UPnP-CAC . for admission control
. Workarounds in network
Static building of multicast trees, SSM transition, DSCP marking, router based CAC, …
Network infrastructure

Only implicitly impacting services (resilience, security,..)
. Preferred choice of transport:
IP (native multicast/PIM) or MPLS (mLDP and RSVP-TE P2MP)
. Path selection
(dual path) . MoFRR or exposed to service
Tree cost optimization
Load-splitting:

ECMP: PIM and mLDP
Arbitrary: RSVP-TE (CSPF)

. Preferred choice of virtualization
L2VPN, L3VPN context . or why not… . …not complete list

Protocols and Services
…and IP multicast

. multicast / multipoint protocols
Between routers, switches, ..
“Only of interest to network operator”
PIM-SM, MSDP, (M)BGP, AutoRP, BSR, mLDP, RSVP-TE, …), IGPs (OSPF, ISIS), …
. multicast services
How end-devices can use IP multicast
“Of interest to network and service operator”
ASM, SSM (and protocols “IGMP/MLD”)
Service operator just need to add SLA requirements!

IP multicast services
. ASM: “Any Source Multicast” (1990, rfc1112) The “traditional IP multicast service” (collaborative) Sources send packets to multicast groups Receivers join to (G) groups, receive from any source
. SSM “source specific multicast” (~2000, rfc4607/4604) The multicast variant for IPTV (or other “content distribution”) Unchanged: Sources send packets to multicast groups Receivers subscribe (S,G) channels,receive only traffic from S sent to G Primarily introduced (by IETF) for IPTV type services Because of limitations of standard (protocol) model for ASM
Standard protocol model for ASM

. What is the standard protocol model ? . A1: MBone and DVMRP
Please go back to your time machine and dial 1994
. A2: Native Multicast with: PIM-SM AutoRP, BSR or MSDP/Anycast-RP redundancy MSDP for Interdomain support Multiprotocol BGP for interdomain RPF selection
Best available general purpose ASM protocol suite …but with issues
IP multicast services Issues with ASM . resolved with SSM
. ASM DoS attacks by unwanted sources Address allocation
. Standard protocol suite
Complexity of protocol operations required PIM-SM (RPT+SPT+Switchover), RP redundancy, announce, location MSDP (RPF), BGP congruency, Interactions with MPLS cores, bandwidth reservation, protection
Scalability, Speed of protocol operations (convergence)
RPT + SPT operations needed

End-to-end protocol viewHistoric development
Aggregation Access Home NetNational
Receiver
content Disk in every
Agg. region

Home STBDSLAMPE-AGG
Regional/ local Gateway content
. Old designs: Use non-IP satellite distribution, inject regional / locally
“National IP network can not transport video (cost, function)”
. Current designs: use regional/local injection only for regional/local content
The national core IP network can transport video perfectly
May also want to feed local/region back across core (national redist)

End-to-end protocol view
example: L3 aggregation

Same choices for all access technologies Different by access technology

Content injection:

IGMPv3 (S,G) membership

PIM-SSM (S,G) joins

STB

L3 Transport Options in clouds:
Opt.Native: PIM-SSM or  MVPN/SSMIGMP:
Source MPLS: LSM / mLDP RSVP-TE {Limits}IGMPv3 IGMPv3 IGMPv3
{Static-fwd}snooping proxy routing SSM
Redundancy
PIM-SSM PIM-SSM PIM-SSM

Transport architectureOverview
. Common deployments: Native PIM-SSM or MVPN

. Concentrate on futures / components
Support for MPLS multicast (LSM) Build P2MP / MP2MP label switched delivery trees mLDP (P2MP, MP2MP), RSVP-TE P2MP Put traffic into a VPN context As a method of service isolation / multiplexing Using L2 vs. L3 on PE nodes To “integrate” better into an L2 service model Redefine PE-PE signaling for MVPN
Overview Elements of transport architecture for tree building
. C(ustomer)-tree building protocols
IPTV: IGMPv3 / PIM-SSM
. P(rovider)-tree (PMSI) building protocols
Native: PIM-SSM/SSM/Bidir, MPLS: mLDP, RSVP-TE
. PE mapping: C-tree(s) to P-tree
1:1/N:1 (aggregation) ; ‘native’/VPN (L2, L3) ; static/dynamic
. PE-PE (“overlay”) tree signaling protocols
Optional PIM or BGP (extensions)
Not needed: native IPv4/IPv6, ‘direct-MDT’ mLDP, static mapping


Combinations with L3 on PE Current widely deployed
. “Native IP multicast” (IPv4/IPv6)
IPv4/IPv6 PIM-SSM in core
User side = core tree: No PE-PE signaling required.
“RPF-Vector” for “BGP free core”

. “MVPN”(PIM)
Carries traffic across RFC2547 compatible L3 VPN. With aggregation IPv4 PIM-SSM/SM/Bidir in core (IPv4) RFC2547 BGP ; GRE encap/encap on PE PE-PE signaling required
I-PMSI = Default-MDT ; SI-PIMSI = Data-MDT
BGP extensions for InterAS and SSM support

Deploying MPLS-Based L3 VPNs and…


Multicast VPN: Challenges
. Multicast not originally supported with MPLS (RFC 2547) . Workaround was point-to-point GRE tunnels from CE to CE . Not scalable with many CE routers
Traffic overhead
Administration overhead

CE CE CECE



MPLS Core
CECE
CE CE

Multicast VPN: Overview


Two Types of MDT Groups
. Default MDT Groups Configured for every MVRF if MPLS or IP core network present Used for PIM control traffic, low bandwidth sources, and
flooding of dense-mode traffic
MI-PMSI (2547bis-mcast)

. Data MDT Groups Optionally configured Used for high bandwidth sources to reduce replication to
uninterested PEs
S-PMSI (2547bis-mcast)

Default MDT: A Closer Look

PIM Control Traffic Flow

Default MDT: A Closer Look

Multicast Data Traffic Flow

Default MDT: A Closer Look

Advantages and Disadvantages

. Advantage: Reduces multicast state in the P routers in the core . Disadvantage: Can result in wasted bandwidth . Solution: Use separate Data-MDTs for high rate sources
Data MDTs: Concepts


. Traffic exceeds Data-MDT threshold configured on PE router

Data MDTs: Concepts


. PE router signals switch to Data-MDT using new group, 239.2.2.1

Data MDTs: Concepts
High-Rate Source

Data MDTs: Concepts


. High-rate data begins flowing via Data-MDT . Data only goes to PE routers that have receivers
Data MDTs: Concepts


MVPN: Supporting Multiple Tree Types
. Key Concept: Separation of a service (PMSI) from its instantiation (tunnels) . Each PMSI is instantiated using a set of one or more tunnels . Tunnels may be built by: PIM (any flavor) mLDP p2mp or mp2mp RSVP-TE p2mp Combining unicast tunnels with ingress PE replication
. Can map multiple PMSIs onto one tunnel (aggregation) . Encaps a function of tunnel, not service . Single provider can mix and match tunnel types
MPLS traffic forwarding
. Same forwarding (HW requirements) with mLDP / RSVP-TE . Initial: “Single label tree” for both non-aggregated & aggregated . No PHP: receive PE can identify tree

MLDP: Transiting SSM (IPv4 Non-VPN)

PIM-V
4 Join:
Source = 10.10.10.1
Group = 232.
0.0.1 4 Source = 0.0.1  M-LDP Lab
el A
dvertisemen
t: FEC = FEC200 RPFv
= PE-1 Label = (100) el dvert t: FEC = FEC200 = PE-1 Label = (100)  M-LDP Lab
el Ad
vertisemen
t: FEC =
FEC200 RPFv
= PE-1 Lab
el = (20) el vert t: FEC200 = PE-1 el = (20)  IPv4 PIM-V
4 JOIN:
Source = 10.10.10.1 Group = 232.
0.0.1 4 Source = 10.10.10.1 0.0.1  CE-2  Content Receiver  
CE-1  IPv4  PE-2  
PE-1  PE-4  
MPLS Core  
Content Source  P2MP LSP “Root”  M-LDP Lab
el A
dvertisemen
t: FEC = FEC200 RPFv
= PE-1 Lab
el = (30) el dvert t: FEC = FEC200 = PE-1 el = (30)  PE-3 PIM-V
4 JOIN:
Source = 10.10.10.1
Group = 232.
0.0.1 4 Source = 0.0.1  IPv4  CE-3  
Content Receiver  

mLDP: Transiting SSM (IPv4 Non-VPN)


Multicast LDP-Based Multicast VPN
(Default-MDT)
MP2MP Tree Setup Summary
4
. All PEs configured for same VRF derive FEC from configured PIM-V
4 VRF Config:

ip vrf RED

default-mdt group

mdt default 239.1.1.1 mp2mp 4.4.4.4

. Downstream path is setuplike a normal P2MP LSP
. Upstream path is set up like a P2P LSP to the upstream router
el el Advertisement: CE-2 Content M-LDP Lab
el IPv4
Advertisement:M-LDP Lab
el FEC-MDT
FEC =
FEC-MDTvert t:
Ad
vertisemen
t:
Receiver
= P-4
FEC= FEC-MDT
RPFv
= P-4 RPFv
= P-4
el = (20)= P-4
Lab
el = (20)
el = (20) (21) Upstrm
Lab
el = (20)

IPv4
PE-2
CE-1
PE-1 PE-4

(21) Upstrm


MPLS Core
el
M-LDP Lab
el
Content dvert t:
A
dvertisemen
t:
Source FEC =
FEC-MDT

FEC-MDT

MP2MP LSP
= P-4
RPFv
= P-4 PE-3

“Root”
el = (30) e IPv4 CE-3 Lab
el = (30)
Lab
el = (31) Upstrm

44
PIM-V
4 VRF Config: PIM-V
4 VRF Config:


ip vrf REDip vrf RED

Content

mdt default 239.1.1.1 mp2mp 4.4.4.4 mdt default 239.1.1.1 mp2mp 4.4.4.4

Receiver
Multicast LDP-Based Multicast VPN

(Default-MDT)

Multicast LDP-Based Multicast VPN

(Default-MDT)

mLDP signaling
Summary . Best of PIM + MPLS
Receiver side originated explicit joins . scalable trees PIM-SSM = mLDP P2MP, Bidir-PIM ~= mLDP MP2MP RPF-vector implicit (mLDP root)
. Best of LDP
Neighbor discovery, graceful restart, share unicast TCP session No interaction for unicast label assignment (ships in the night)
. Variable length FEC
Allows overlay signaling free 1:1 tree building for ANY (vpn, v6,..) tree
. All PIM complexity avoided
No direct source/receiver support (DR) (just PE to PE) No PIM-SM (need to emulate), No Bidir-PIM DF process No hop-by-hop RP config (AutoRP, BSR, static) needed) No asserts, other data-triggered events
Combinations with L3 on PE with RSVP-TE P2MP
. RSVP-TE P2MP static / native
Core trees statically provisioned on Headend-PE: Set of tailend-PE All IP multicast traffic that need to be passed into the tree.
. RSVP-TE P2MP static in L3VPN context TBD: Possible, some more per-VRF/VPN config
. RSVP-TE P2MP dynamic TBD: MVPN or new PE-PE signaling (work in IETF, vendors) Required / beneficial ?
Reason for RSVP-TE often explicit path definition Not as easy predictable dynamic as static
RSVP-TE P2MP signalingwith static native IPv4 to customer

P2MP RSVP-TE Summary
. RSVP-TE P2P LSP
Path explicitly (hop-by-hop) built by headend LSR towards tailend LSR RSVP PATH messages answered by RESV message
. P2MP RSVP-TE LSP
A P2MP LSP is built by building a P2P LSP for every tailend of P2MP LSP Midpoint LSR performs “label merge” during RESVP: Use same upstream label for all branches
. Almost all details shared with RSVP-TE P2P
All RSVP parameters (for bandwidth reservation)
ERO or CSPF, affinities
link protection
Node protection more difficult

PIM/mLDP benefits over RSVP-TE P2MP
Examples

. Cost of trees (in node/network)
Src
N = # tailend LSR (#PE)
PIM/mLDP P2MP: ~1,  RSVP-TE P2MP: ~N
Full mesh of RSVP-TE P2MP LSP: ~(N * N)
Bidir-PIM/mLDP MP2MP: ~1
Summary: No scaling impact of N for PIM/mLDP

. Locality: Affects convergence/reoptimization speed: PIM/mLDP: Failure in network affects only router
in region (eg: in pink region).
RSVP: impact headend and all affected midpoint
and tailends for RSVP-TE reoptimization.
Join/leave of members affect only routers up to

first router on the tree in mLDP/PIM. Will affect Rcv headend and all midpoints in RSVP-TE P2MP. Rcv


RSVP-TE P2MP benefits over PIM/mLDP
Examples
. Sub 50 msec protection Src
. Load-split traffic across alternative paths (ECMP or not) PIM/mLDP tree follows shortest path, “dense” receiver population == dense use of links RSVP-TE P2MP ERO trees (RED/PINK) under control of headend LSR. CSPF load split based on available bandwidth. “Steiner tree” CSPF modifications possible
. Block (stop) trees on redundancy loss Assume high-prio and low-prio trees. With full redundancy, enough bandwidth to carry
all trees (with load-splitting)
On link-loss, reconverge high-prio, block low-prio Rcv


Combining RSVP-TE P2MP and mLDP
. Rule of thumb:
Src
Think of mLDP and RSVP-TE P2MP as multicast  
versions of unicast counterparts (LDP, RSVP-TE)
Use whenever unicast equivalent is used.

. Can run RSVP-TE P2MP and mLDP in parallel Each one running PE-PE . ships in the night !
. Can not combine RSVP-TE P2MP / mLDP along path !!!
Standard unicast design: full mesh RSVP-TE
between P nodes, LDP on PE-P links.
Limit size of full-mesh (RSVP-TE scalability)
Multicast: to map mLDP tree onto RSVP-TE P2MP tree, P
nodes would need to logically be ‘PE’ . running all PE-PE
signaling (eg: P node running BGP-join extensions).
NOT DESIGNED / SUPPORTED
Static designs with PIM PE-P possible though(and RSVP-TE between P nodes) Rcv

L2VPN Considerations
. L2 preferred by non-IP ‘communities’ IP address transparency (unicast only issue) PE “invisible” = customer free to choose protocols independent
of provider
Not true if PE uses PIM/IGMP snooping!

. No (dynamic) P/PE L2 solution with P2MP trees VPLS: full-mesh/hub&spoke P2P pseudowire only Non P/PE models available: single-hop protected pseudowires Recommended directions:
TBD: define how to use mLDP for L2VPN (VPLS) Most simple: one mLDP MP2MP LSP per L2VPN (broadcast) Recommend not to use IGMP/PIM snooping on L2VPN-PE! Unless customer is provider (e.g., broadband-edge design)
Transit technologies for IPTV
Summary / recommendations

. Native PIM-SSM + RPF-Vector Most simple, most widely deployed, resilient solution.
. PIM based MVPN Also many years deployed (IOS, JUNOS, TIMOS). Recommended for IPTV when VRF-isolation necessary
. mLDP Recommended Evolution for MPLS networks for all IP multicast transit:
‘Native’ (m4PE/m6PE)
‘Direct-MDT/MVPN-mLDP’ (IPv4/IPv6)

. RSVP-TE P2MP Strength in TE elements (ERO/CSPF + protection) Recommended for limited scale, explicit engineered designs,
eg: IPTV contribution networks.

End-to-end protocol viewDSL, L3 aggregation


{Static-fwd}
Redundancy
PIM-SSM PIM-SSM PIM-SSM
End-to-end protocol viewDSL, L2 aggregation
Same choices for all access technologies Different by access technology



PIM-SSM

(S,G) joins


IGMP: IGMPv3 IGMPv3 IGMPv3 IGMPv3 IGMPv3{Limits}snooping snooping snooping proxy routing SSM{Static-fwd}
PIM-SSM
IGMP snooping vs. proxy routing


. IGMP snooping: IGMP
Performed by L2 switch. Intended to the Proxy routing transparent. Many vendor variations.
IETF RFC 4541 . INFORMATIONAL ONLY
Transparent: no snooping messages suppressed

Report-suppression: guess which IGMP reports
are redundant at router (can break explicit
tracking, fast leaves).

IGMP
Proxy-reporting: fully emulate host. Proxying
Router

IGMPv3: Use source-IP address “0.0.0.0”

. IGMP proxy-routing:
Performed by router:
IETF RFC4605 . STANDARDS TRACK
IGMP proxy router need to act exactly like a
single host on it’s upstream interface.

Router can not transparently pass trough IGMP
membership packets from downstream hosts: would
have incorrect source-IP addresses.


End-to-end protocol viewdigital cable (non DOCSIS)


{Static-fwd}
Redundancy
PIM-SSM PIM-SSM PIM-SSM
End-to-end protocol view

DOCSIS 3.0 cable



PIM-SSM

Auto Multicast Tunneling (AMT)
. Tunnel through non-multicast enabled network segment Draft in IETF ; Primarily for SSM GRE or UDP encap Relay uses well known ‘anycast’ address . Difference to IPsec, L2TPv3, MobileIP, … Simple and targeted to problem Consideration for NAT (UDP) Ease implemented in applications (PC/STB) (UDP) . Variety of target deployment cases Relay in HAG . provide native multicast in home Gateway in core-SP . non-multicast Access-SP Access-SP to Home -non-multicast DSL In-Home only . eg: multicast WLAN issues


Failure Impact Upon Viewer Experience

. Very hard to measure and quantify . If I frames or frame-information is lost, impact will be for a whole GOP GOP can be 250 msec (MPEG2) .. 10 sec (WM9)
. Encoding and intelligence of decoder to “hide” loss impact quality as well
. IP/TV STB typically larger playout buffer than traditional non-IP STBs: Loss can cause catch-up: no black picture, but just a jump in the motion
. What loss is acceptable? Measured in number of phone calls from complaining customers?!
Impact of Packet Loss on MPEG Stream


. Compressed Digitized Video is sent as I, B, P Frames
. I-frames: Contain full picture information

Transmit I frames approximately every 15 frames (GOP interval)
. P-frames: Predicted from past I or P frames
. B-frames: Use past and future I or P frames

I-Frame Loss “Corrupts” P/B Frames for the Entire GOP

IP/TV Deployments Today
. Two schools of thought in deployments today: I think I need 50ms convergence IPMulticast is fast enough
. IPMulticast is UDP The only acceptable loss is 0ms How much is “reasonable”?
. 50ms “requirement” is not a video requirement Legacy telco voice requirement Efforts for 50ms only cover a limited portion network events
. Where to put the effort? Make IPMulticast better? Improve the transport? Add layers of network complexity to improve core convergence?
Application Side Resiliency
. FEC: Forward Error Correction Compensate for statistical packet loss Use existing FEC, e.g. for MPEG transport to overcome N msec
(>= 50 msec) failures?
Cover loss of N[t] introduces delay > N[t]!

. Retransmissions
Done e.g. with vendor IP/TV solutions.unicast retransmissions Candidate large bursts of retransmissions! Limit #retransmissions necessary
Multicast retransmissions (e.g. PGM ?)
No broadcast IP/TV solutions use this

Service Availability Overview
IP Host Components Redundancy . Single transmission from Logical IP address Anycast.Use closest instance Prioritycast.Use best instance Benefit over anycast: no synchronization of sources needed, operationally easier to predict which source is used Signaling host to network for fast failover RIPv2 as a simple signaling protocol Normal Cisco IOS/IGP configuration used to inject these source server routes into the main IGP being used (OSPF/ISIS)
. Dual Transmission with Path separation
Video Source Redundancy:Two Approaches

. Receiver’s functionality simpler: Aware of only one src, failover logic handled between sources  . Receiver is smarter: Is aware/configured with two feeds (s1,g1), (s2,g2) / (*,g1), (*,g2) Joins both and receives both feeds  
. This approach requires the network to have fast IGP and PIM convergence  . This approach does not require fast IGP and PIM convergence  

Source Redundancy:Anycast/Prioritycast Signaling
. Redundant sources or NMS announce Source Address via RIPv2 . Per stream source announcement . Routers redistribute (with policy) into IGP Easily done from IP/TV middleware (UDP) No protocol machinery required.only periodic announce packets

Small periodicity for fast failure detection Router All routers support RIPv2 (not deployed as IGP):
Allows secure constrained configuration on routers
Anycast-Based Load Balancing


Encoder Failover Using Anycast


Source Redundancy
Anycast/Prioritycast Policies
. Policies
Anycast: Clients connect to the closest instance of redundant IP address
Prioritycast: Clients connect to the highest-priority instance of the redundant IP address
. Also used in other places
e.g. PIM-SM and Bidir-PIM RP redundancy
. Policy simply determined by routing announcement and routing config Anycast well understood Prioritycast: Engineer metrics of announcements or use different prefix length
ⓒ 2008 Cisco Systems, Inc. All rights reserved.
Src A Src B Primary Secondary 10.2.3.4/32 10.2.3.4/31




Rcvr 1 Rcvr 2
Example: Prioritycast with Prefixlength Announcement
Source Redundancy
Anycast/Prioritycast Benefits
. Sub-second failover possible . Represent program channel as single (S,G) SSM: single tree, no signaling; ASM: no RPT/SPT . Move instances “freely” around the network Most simply within IGP area
Regional to national encoder failover (BGP…)? . No vendor proprietary source sync proto required . Per program, not only per-source-device failover
Use different source address per program
FRR for Native IP Multicast/mLDP

. Do not require RSVP-TE for general purpose multicast deployments . Sub 50 msec FRR possible to implement for PIM or mLDP Make-before-break during convergence Use of link-protection tunnels Initial: one-hop RSVP-TE P2P tunnels Future: NotVia IPFRR tunnels (no TE needed then)
MoFRR
. It is make-before-break solution . Multicast routing doesn’t have to wait for unicast routing to converge . An alternative to source redundancy, but: Don’t have to provision sources Don’t have to sync data streams No duplicate data to multicast receivers
. No repair tunnels . No new setup protocols . No forwarding/hardware changes
Concept Example

Not Wasted Bandwidth

7.         If upstream of D there are receivers, bandwidth is only wasted from that point to D


Interface in oif-list


Link Down or RPF-Failed Packet Drop



Multicast Fast Convergence
. IP multicast
All failures/topology changes are corrected by re-converging the trees Re-convergence time is sum of:
Failure detection time (only for failure cases)
Unicast routing re-convergence time
~ #Multicast-trees PIM re-convergence time
Possible
~ minimum of 200 msec initial
~ 500 ... 4000 trees convergence/sec (perf)
. Same behavior with mLDP
Multicast Node Protection
with p2p Backup Tunnels

. If router with fan-out of N fails, N-times as much backup bandwidth as otherwise is needed
Provisioning issue depending on topology! . Some ideas to use multipoint backup to resolve this, but… . Recommendation? Rely on Node HA instead!!

Multicast HA for SSM:
Triggered PIM Join(s)


Periodic PIM Joins GENID PIM Hello Triggered PIM Joins
How Triggered PIM Join(s) Work When Active Route Processor Fails:
.         Active Route Processor receives periodic PIM Joins in steady-state
.         Active Route Processor fails
.         Standby Route Processor takes over
.         PIM Hello with GENID  is sent out
.         Triggers adjacent PIM neighbors to resend PIM Joins refreshing state of distribution tree(s) preventing them from timing out
Multi-Topology (MT)-Technologyand IP Multicast
. … When not all traffic should flow on the same paths . Interdomain: Incongruent routing BGP SAFI2 (MBGP)
. Intradomain: Incongruent routing workarounds Static mroutes Multiple IGP processes (tricky)
. Intradomain: Multi-Topology-Routing Multicast and Unicast solution; multiple topologies for unicast and multicast
. Intradomain: MT-technology for multicast
Subset of MTR: Only the routing component, sufficient for incongruent routing for IP multicast
MBGP Overview
MBGP: Multiprotocol BGP
. Defined in RFC-2283 (extensions to BGP) . Can carry different types of routes
IPv4/v6 Unicast/Multicast
. May be carried in same BGP session
. Does not propagate multicast state information
Still need PIM to build Distribution Trees
. Same path selection and validation rules AS-Path, LocalPref, MED, …
MBGP Update Message
. Address Family Information (AFI)
Identifies Address Type (see RFC-1700)
AFI = 1 (IPv4)
AFI = 2 (IPv6)

. Sub-Address Family Information (Sub-AFI) Sub-category for AFI Field Address Family Information (AFI) = 1 (IPv4)
Sub-AFI = 1 (NLRI is used for unicast)
Sub-AFI = 2 (NLRI is used for multicast RPF check)

MBGP: NLRI Information

Unicast BGP Table
Network Next-Hop      Path*>i160.10.1.0/24   192.20.2.2    i*>i160.10.3.0/24   192.20.2.2    i*>i192.192.2.0/24  192.168.200.2 300 200 i
BGP Update from Peer
MP_REACH_NLRI: 192.192.2/24
AFI: 1, Sub-AFI: 1 (unicast)

AFI: 1, Sub-AFI: 1 (u

Multicast BGP Table
AS_PATH: 300 200
MED:

Network Next-Hop      PathNext-Hop: 192.168.200.2
*>i160.10.1.0/24   192.20.2.2    i*>i160.10.3.0/24   192.20.2.2    i
Storage of arriving NLRI information depends on
AFI/SAFI fields in the Update message



. Unicast BGP Table only (AFI=1/SAFI=1 or old style NLRI)
MBGP: NLRI Information

BGP Update from Peer
MP_REACH_NLRI: 192.192.2/24
AFI: 1, Sub-AFI: 2 (multicast)

AFI: 1, Sub-AFI: 2 (multicast)
AS_PATH: 300 200
MED:
Next-Hop: 192.168.200.2

Unicast BGP Table
Network Next-Hop      Path*>i160.10.1.0/24   192.20.2.2    i*>i160.10.3.0/24   192.20.2.2    i

Multicast BGP Table
Network Next-Hop      Path*>i160.10.1.0/24   192.20.2.2    i*>i160.10.3.0/24   192.20.2.2    i*>i192.192.2.0/24  192.168.200.2 300 200 i
Storage of arriving NLRI information depends on
AFI/SAFI fields in the Update message
. Unicast BGP Table only (AFI=1/SAFI=1 or old style NLRI)
. Multicast BGP Table only (AFI=1/SAFI=2)

Multi-Topology Routing (MTR)
Full Solution with Both MT-Technology Routingand Forwarding
Base Topology Voice Topology Start with a Base TopologyMulticast Topology Includes All Routers and All Links

. Define traffic-class specific topologies across a contiguous subsection of the network . Individual links can belong to multiple topologies
Applications for Multiple Topologiesfor IP Multicast
. Original MTR Reasons Different QoS through choice of different paths:
Well applicable to multicast: Low-latency and low-loss: hoot&holler/IPICs multicast Low-latency: finance market-data (stream redundancy against loss) High-bandwidth: ACNS content provisioning network Low-loss: video
Not too critical: Most networks today only run one type of business critical multicast apps (about to change?!)
. Live-Live with Path Diversity Also called stream redundancy with path separation Examples shown in various stages of deployment with other approaches or
workarounds to multi-topology multicast But multicast with multiple topology considered most easy/flexible approach
to problem

Live-Live
. Live-Live.Spatial Separation
Two separate paths through network; can engineer manually
(or with RSVP-TE P2MP )
Use of two topologies (MTR)
“Naturally” diverse/split networks work well (SP cores,

likely access networks too), especially with ECMP
Target to provide “zero loss” by merging copies based
on sequence number

. Live-Live.Temporal Separation
In application device.delay one copy.need to know maximum network outage
What Is Live-Live (with Path Diversity)?

. Transport same traffic twice across the network… Receivers can merge traffic by sequence-number
. … On diverse paths to achieve the Live-Live promise:

Every single failure in the network will only affect one copy of the traffic

Receiver

What Is Live-live (with Path Diversity)?

. Why bother?
Only resiliency solution in the network that that can be driven to provide zero packet loss under any single failure in the network. without introducing more than path propagation delay (latency)!
. Much more interesting for multicast than unicast Individual unicast packet flow typically for just one receiver Individual multicast flow (superbowl) for N(large) receivers!
. Path diversity in the network Lots of alternatives: VRF-lite, routing tricks, RSVP-TE, L2 VLAN Multi-topology routing considered most simple/flexible approach!
. Standard solution in finance market data networks Legacy: Path diversity through use of two networks!
Cable Industry Example
STBs

STBs
. Path separation does not necessarily mean separate parts of network!
Carrying copies counterclockwise in rings allows single ring redundancy
to provide live-live guarantee; less expensive network

. Target in cable industry (previously used non-IP SONET rings!)
IP live-live not necessarily end-to-end (STB), but towards Edge-QAM (RH*). merging traffic for non-IP delivery over digital cable
With path separation in IP network and per-packet merge in those devices
solution can target zero packet loss instead of just sub 50msec

Protected pseudowires



Classic pseudowire
.         R1/R2 provide pseudowire
for R3/R4
accepting/delivering packets
from/to physical interface.

Protected pseudowire
.         Provide sub 50msec link
protection for packets of
pseudowire (or any other
MPLS packets) by
configuring RSVP-TE LSP
with FRR backup tunnel

Terminated pseudowire
.         R1/R2 terminate
pseudowire on internal port
instead of physical
interface. Can bridge
(VLAN) or route from/to
port.

ⓒ 2008 Cisco Systems, Inc. All rights reserved.

R4

R4

over LDP MPLS
cFRR PIM/mLDP Break before Make
Cost: 10
A




S(ource) Cost: 12

B



RPF change on C from A to C: 1.Receive RPF change from IGP 2.Send prunes to A 3.Change RPF to B 4.Send joins to B Same methodology, different
terminology in mLDP RPF == ingres label binding Some more details (not discussed)
cFRR PIM/mLDP Make before Break
Cost: 10
A



S(ource) Cost: 12

B



1.
Receive RPF change from unicast

2.
Send joins to A


3. Wait for right time to go to 4. Until upstream is forwarding traffic
4.
Change RPF to A

5.
Send prunes to B Should only do Make-before-Break when old path


(B) is known to still forward traffic after 1.
Path via B failed but protected
Path to A better, recovered
Not: path via B fails, unprotected

Make before Break could cause more interruption than Break before Make !

MT-IGP
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
ⓒ 2008 Cisco Systems, Inc. All rights reserved.
.         Regions use ring(s) for redundant connectivity
MT-IGP
Cost optimization

Rcvr
Rcvr
Rcvr
Src2

MT-IGP
Cost optimization
Rcvr
Rcvr
Src2

MT-IGP
Cost optimization
Rcvr
Rcvr

Rcvr
Src2
. 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 (loss of A connectivity)
IP multicast (and mLDP) ECMPnon-polarizing means non-predictable . Polarization:
All routers along network path choose same relative interface for amulticast tree.
. Predictability: With algorithm known, group addresses G of (S,G) can be assigned by operator such that traffic is well split across multiple hops (link bundles)
Workaround, not recommended . for highly utilized links (> 85% ?)

IP multicast (and mLDP) ECMP stability, consistency
. Multicast ECMP different from unicast:
Unicast ECMP non-polarizing, but also non-
stable, non-consistent.
Not a problem for unicast, but multicast:

. Stability If path fails only trees on that path will need toreconverge. If path recovers, only trees that willuse the new path will reconverge
Polarizing multicast algoritm is NOT stable! . Consistency Multiple downstream router on same LAN (R4,
R5) will select same upstream router. Avoids “assert” problem in PIM-SSM Polarizing multicast ECMP also consistent.

. mLDP targeting same algorithms
No Assert problems though…

Path selection review RSVP-TE/P2MP
. CSPF/ERO “Traffic Engineering”(bandwidth, priority and affinity based path selection) . Very powerful “can do everything we can think of” . “Offline” management (ERO) most common Network provider incooperates “off-network” information about necessary multipoint trees . “Online” / CSPF based path selection
Ideal for single headends.
How much better than SPF without coordinated CSPF for
multiple headends ?

Network wide coordinated CSPF calculation TBD
Path selection review PIM (native multicast) / mLDP
. Can not load split across non-equal-cost paths
. Path engineering with topologies and ECMP: . ECMP best when multipoint traffic << link bandwidth (30%?) Higher utilization deployments . special considerations(due to statistical chance of congestion)
. Topologies Single incongruent topology . cost opt / route around obstacles. Two topologies for path separation (live-live) Could use more topologies for more functionality . eg: non-equal­
cost load-splitting . but maintaining many topologies likely not less complex than RSVP-TE
Note: MT-technology for multicastonly happens in control plane. No forwarding plane impact

Static vs. dynamic trees
1. “Broadcast Video”
Dynamic IGMP forward up to DSLAM
DSL link can only carry required program!
static forwarding into DSLAM
Fear of join latency

History (ATM-DSLAM)
2. “Switched Digital Video”
Allow oversubscription of PE­AGG/DSLAM link

3. “Real Multicast”
dynamic tree building full path

Switched Digital Video


Why oversubscription of access links makes sense
. Switched Digital Video
Consider 500…1000 users on DSLAM Consider 300 available TV programs Monitor customer behavior . what is being watched ?
Example (derived from actual MSO measurements)

Some 50 TV programs almost always watched (big
channels)
Out of remaining 220 TV programs never than ¼ watched
Never need more bandwidth than ~ 125 channels!

. Dynamic joining towards core ?
Todays offered content << #users aggregated -> worst case traffic will always flow.
More a provisioning issue . and when content expands well beyond current cable-TV models
Admission control
. Congestion must be avoided
Inelastic: TV traffic can not throttle upon congestion
One flow too many disturbs all flows
Need to do per TV-flow admission control

. Router-links
Router local CLI solution
Strategic solution: RSVP
Already used for unicast VoD
Can only share bandwidth between unicast and multicast with
RSVP
. Broadband access (DSL link, Cable)
Issues with L2 equipment (eg: DSLAM)
Multicast Call Admission Control

Example CAC use: 1. Three CPs  Content Providers  Service Provider  250-500 users per DLAM PayingCustomers  
2.  Different BW:  Content  

Provider 1
-MPEG2 SDTV: 4 Mbps
DSLAM
MPEG2 SDTV
MPEG2 HDTV
MPEG4 SDTV

-MPEG2 HDTV: 18 Mbps
MPEG4 SDTV
-MPEG4 SDTV: 1.6 Mbps -MPEG4 HDTV: 6 Mbps Content
1GE

10GE

Provider 2
MPEG2 SDTV
MPEG2 HDTV
3. Fair sharing of bandwidth
MPEG4 SDTV
PE

MPEG4 SDTV DSLAM
Content
4. 250 Mbps for each CP
Provider 3
MPEG2 SDTV

250 Mbps Internet/etc
MPEG2 HDTV MPEG4 SDTV
MPEG4 SDTV
DSLAM
5. Simply add global costs
Broadband link access, admission control



. No IGMP snooping (replication) on DSLAM
BRAS
PE-AGG access/admission control on PE-AGG link
affects only single subscriber == equivalent to do
access/admission control on DSL link.

Or BRAS (if traffic not native but via PPPoE tunnel
. IGMP snooping on DSLAM
PE-AGG
PE-AGG stopping multicast traffic on PE-AGG link will
affect all subscriber. Only DSLAM can control DSL link

PE-AGG
multicast traffic
link
. IP Multicast extensions to ANCP
DSLAM
(Access Node Control Protocol) ANCP

DSL
Work in IETF
link
In IGMP snooping on DSLAM, before forwarding,
request authorization from ANCP server.

Allow ANCP server to download access control list to
DSLAM.

. Similar model as defined in DOCSIS 3.0

CMTS controls CM



Join Latency
. Static forwarding (to PE-AGG, or DSLAM) To avoid join latency Sometimes other reasons too (policy, …)
. Bogus ?
Hop-by-hop Join latency (PIM/IGMP) very low,
eg: individual < 100 msec …
Joins stop at first router/switch in tree that already forwards tree
Probability for joins to go beyond PE-AGG very low !

If you zap to a channel and it takes ¼ sec more: You are the first guy watching this channel in a vicinity of eg: 50,000 people. Are you sure you want to watch this lame program ?
. Important
Total channel zapping performance of system . Primetime TV full hour or (often synchronized) commercial breaks.
Join latency during bursts might be worse than on average. (DSLAM performance)
IGMPv2 leave latencyObsolete problem
. Congesting issues due to IGMPv2 leave latency when only admission control mechanism is: DSL link fits only N TV programs … and subscriber can only have N STB.
. Example:
4Mbps DSL link, 3.5 Mbps MPEG2
Can only receive one TV channel at a time
Leave latency on channel change complex (triggers IGMP
queries from router/DSLAM) and long (spec default: 2 seconds)
. Resolved with IGMPv3/MLDv2
Ability for explicit tracking (vendor specific)
Can immediately stop forwarding upon leaves
Channel ChangingGOP size and channel changing
. GOP size of N seconds causes channel change latency USER EXPERIENCE >= N seconds
Can not start decoding before next I-frame
. Need/should-have channel change acceleration for GOP sizes > 0.5 sec ?
. Many codec dependencies:
How much bandwidth is saved in different codecs by raising GOP size but keep the quality.
Video Quality Experience


. Three functions (currently): Video Quality monitoring, FEC/ARQ support for DSL links, Fast Channel change
. Uses standards RTP/RTCP, FEC extensions.
. Fast channel channel by RTCP “retransmission” triggered resend of missing GOP packets from VQE (cached on VQE).

Multicast and IPTV Summary
. Design IP multicast WITH SSM as generic infrastructure service .for IPTV and beyond . Select transport design Native IP multicast or mLDP (MPLS core) for most networks RSVP-TE P2MP for eg: contribution network . Understand your L2 broadband edge specifics IGMPv3 snooping and SSM + lots of options . Determine appropriate resilience support . Path selection ECMP and multicast or multiple topologies . Admission control Router local and broadband specific . Channel changing GOP size, total performance
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