multicast 2
Download
Skip this Video
Download Presentation
Multicast 2

Loading in 2 Seconds...

play fullscreen
1 / 53

Multicast 2 - PowerPoint PPT Presentation


  • 282 Views
  • Uploaded on

Multicast 2. 2002 년 4 월 2 일 Jeong Ji-Woong. Outline. Introduction Overview of IP Multicast Hop By Hop Multicast End System Multicast Conclusion. What is multicast?. Delivery of Data one-to-many, many-to-many Application 인터넷 방송 ftp Video-conferencing, shared whiteboard benefit

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Multicast 2' - artie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
multicast 2

Multicast 2

2002년 4월 2일

Jeong Ji-Woong

outline
Outline
  • Introduction
    • Overview of IP Multicast
  • Hop By Hop Multicast
  • End System Multicast
  • Conclusion
what is multicast
What is multicast?
  • Delivery of Data
    • one-to-many, many-to-many
  • Application
    • 인터넷 방송
    • ftp
    • Video-conferencing, shared whiteboard
  • benefit
    • Reducing network load
    • Reducing server overhead
      • Single transmission
multicast vs unicast
Multicast vs Unicast

Server

Network

Client

Server

Network

Client

class d address
Class D address
  • Class D : 224.0.0.0 ~ 239.255.255.255
  • Well known address
    • Reserved : 244.0.0.0~224.0.0.255(topology discovery,maintenance)
    • 224.0.0.1 : all multicast systems on subnet
    • 224.0.0.2 : all routers on subnet
  • Map into Ethernet:01.00.5E.00.00.00+lower 23bits
    • 224.10.8.5 → 01005E.0A0805
fundamental algorithms
Fundamental algorithms
  • Multicast Routing algorithm
    • Reverse Path Broadcasting(RPB)
    • Truncated Reverse Path Broadcasting(TRPB)
      • RPB+truncated
      • group member를 가지지 않은 leaf로는 forwarding하지 않음
    • Reverse Path Multicasting(RPM)
      • TRPB+prune
      • TRPB를 이용하여 multicast packet을 forwarding
      • member가 없는 leaf router는 source를 향하여 prune 메시지를 전송
fundamental algorithms1
Fundamental algorithms
  • join algorithm
    • Implicit join: source로부터 multicast packet이 도착 후 tree 형성
    • explicit join: host가 router 또는 source를 향해 join message 를 전송함으로써 트리 형성
ip multicast routing protocol
IP Multicast Routing Protocol
  • DVMRP(Distance Vector Multicast Routing Protocol)
  • MOSPF(Multicast Extensions to OSPF)
  • PIM-DM(Protocol Independent Multicast-Dense Mode)
  • CBT(Core Based Tree)
  • PIM-SM(Protocol Independent Multicast-Sparse Mode)
source based tree sbt
Source Based Tree(SBT)
  • DVMRP
    • Operation
      • RPM + grafting
      • DVMRP router 간의 주기적인 routing table update
  • PIM-DM
    • Similar to DVMRP
  • MOSPF
    • OSPF link state routing protocol에 의해서 topology 파악
    • Explicit join
  • Drawback
    • 주기적인 multicast traffic이 전체 network으로 전송
    • Not scalable(member 수가 증가함에 따라)
center based tree cbt
Center Based Tree(CBT)
  • CBT
    • group내의 모든 member는 같은 tree를 공유(shared tree)
    • Bidirectional tree
    • Explicit Join
  • PIM-SM
    • Similar to CBT
    • Unidirectional tree
      • source에서 RP로 tunneling
  • Drawback
    • Multicast packet을 전송할 때 delay가 커진다.
    • core 또는 Rendezvous Point 근처에서 bottleneck
example1
Example
  • JOIN REQUEST
example2
Example
  • CBT Forwarding
outline1
Outline
  • Introduction
  • Hop By Hop Multicast
    • REUNITE
    • HBH
  • End System Multicast
  • Conclusion
ip multicast component
IP Multicast component
  • Service Model
    • 여러 Receiver들이 하나의 주소를 가지는 Group으로 Aggregate 됨
    • 어떤 호스트도 Receiver들의 Group으로 전송가능
    • Receiver들은 Dynamic하게 Join과 Leave가 가능
  • Routing Protocol
    • Membership Information의 유지
    • Multicast Distribution Tree의 형성
problem of ip multicast
Problem of IP Multicast
  • 기존 Service Model의 문제점
    • 일반적인 ISP의 Billing Model과 맞지 않음
    • Sender를 제한할 수 있는 방법이 없음
    • Globally Unique한 Multicast 주소 할당의 어려움
  • 기존 Routing Protocol의 문제점
    • 모든 Router는 Distribution Tree가 자신을 지나가는 모든 Group에 대한 Forwarding Entry를 가지고 있어야 함
    • Incremental Deployment의 어려움
reunite
기존 Routing Protocol의 문제점

모든 Router는 Distribution Tree가 자신을 지나가는 모든 Group에 대한 Forwarding Entry를 가지고 있어야 함

Assuming

Multicast Group들의 수는 많아도 대다수의 Group들은 대단히 Sparse 할 것

REUNITE
forwarding algorithm
Forwarding Algorithm
  • Multicast Forwarding Table
    • Key : <root_addr, root_port, dst>
    • Value : <rcv1, rcv2, …, rcvn>
    • Branching Router에 존재
  • Forwarding Algorithm
    • MFT에 Entry가 존재하면 Receiver List에 있는 Receiver에게 Packet을 복사해서 전송
    • 단순한 Unicast Packet 처럼 전송
tree maintenance
Tree Maintenance
  • Multicast Control Table
    • Format : <root_addr, root_port><dst>
    • Non-Branching Router에 존재
  • Question
    • 결국 REUNITE도 MFT나 MCT 둘 중의 하나를 모든 Router들이 가지고 있는데 왜 더 Scalabe 한가?
  • Answer
    • Data Packet은 Forwarding 시 MFT 만을 참조
    • MCT는 Tree 유지를 위한 Control 목적으로만 사용
tree maintenance1
Two Control Messages

JOIN (Receiver->Root) : MFT의 Receiver Entry를 만들고 갱신

TREE (Root->Distribution Tree) : MFT와 MCT의 Group Entry를 만들고 갱신

두 가지 Control Message를 쓰는 이유

Asymmetric Unicast Routes

Tree Maintenance

S

1

2

R

R

advantages
Advantages
  • Enhanced Scalability
    • Non-Branching Router에는 Forwarding State를 유지하지 않음
  • Incremental Deployment
    • Unicast Address를 사용하기 때문에 Multicast가 구현되지 않은 Router가 Tree에 참여 가능
  • Load Balancing
    • Overload된 Router는 JOIN Message를 무시할 수 있음
advantages1
Advantages
  • Unique Group Identification
    • Root가 Locally Unique한 Port Number를 만들면 Globally Unique한 Group Address가 됨
  • Support for Access Control
    • Root만이 Multicast Traffic을 Inject할 수 있기 때문에 Access Control이 용이
  • Shortest Path Tree
    • JOIN과 TREE의 두 Message를 사용함으로써 Asymmetric Routes가 존재하는 경우에도 SPT를 구성
reunite s problem
REUNITE’s Problem
  • Addressing
    • Group Identifier로 Class-D Address를 쓰지 않음
  • Member Departure의 효과
    • 첫 번째로 JOIN한 Receiver가 Deparutre할 경우 그 파급 효과가 큼
reunite s problem1
REUNITE’s Problem
  • Asymmetric Routes에 의한 Packet Duplication
    • 한 Link로 같은 Packet을 두 번 전송하는 경우가 발생
    • RPF 기반 Algorithm에 비해 Cost가 클 수 있음
hbh s addressing
HBH’s Addressing
  • REUNITE와 차이점
    • Data Packet의 Destination Address가 첫 번째의 Receiver의 Address가 아닌 다음 Branching Router의 Address
  • Multicast Group Identifier
    • EXPRESS의 Channel Abstraction을 사용
    • <Source IP Address, Class D address>
hbh s tree management
HBH’s Tree Management
  • Three Control Messages
    • JOIN (Receiver->Source) : MFT의 Receiver Entry를 만들고 갱신
    • TREE (Sender->Distribution Tree) : MFT와 MCT의 Group Entry를 만들고 갱신
    • FUSION (Branching Router->Source) : Tree 구조를 정제
  • REUNITE와 차이점
    • 첫 번째 JOIN Message를 Intercept하지 않음
    • 같은 Source에게 다른 TREE Message를 받으면 Source에게 FUSION Message를 보냄
hbh s tree management2
HBH’s Tree Management
  • Member Departure의 효과
    • 첫 번째로 JOIN한 Receiver가 Departure할 경우에도 작은 파급 효과
    • Worst Case에는 REUNITE보다 하나 많은 Change 필요
  • Asymmetric Routes에 의한 Packet Duplication
    • FUSION Message로 해결
outline2
Outline
  • Introduction
  • Hop By Hop Multicast
  • End System Multicast
  • Conclusion
key concerns with ip multicast
Key Concerns with IP Multicast
  • group의 수에 따른 scalability
    • Router는 per-group state를 유지
  • higher level functionality를 지원하기가 어려움
    • IP Multicast : best-effort multi-point delivery service
  • Deployment가 어렵고 느리다
ip multicast

routers

end systems

multicast flow

IP Multicast
  • 아주 효율적
  • Good delay
what is end system multicast

B

C

C

Overlay Tree

D

B

A

D

E

A

F

E

F

What is End System Multicast?
  • multicast와 관련된 functionality (group management, packet replication) 가 End System에서 구현
end system multicast

A

A

A

B

B

B

C

C

C

E

E

D

D

D

E

F

F

F

High latency

High degree (unicast)

“Efficient” overlay

End System Multicast
  • Efficient overlay tree
    • low stress
    • low resource usage
    • the out-degree of each member must reflect the bandwidth of connection to Internet
end system multicast1
End System Multicast
  • Self-organizing의 two component
    • group management component
      • overlay는 dynamic change와 failure 에도 robust
    • overlay optimization component
      • quality of overlay remains good
narada design
NARADA Design
  • First,
    • “Mesh”: Richer overlay that may have cycles and includes all group members
  • Second,
    • Source rooted shortest path spanning trees of mesh를 구성
narada design1
NARADA Design
  • Group Management
    • 각각의 member는 주기적으로 refresh message를 발생
  • Optimizing mesh quality
    • addition of link
      • member는 주기적으로 다른 member(at random)를 probe
      • Utility Gain of adding link > Add Threshold 이면 link 추가
    • dropping of link
      • member는 주기적으로 existing links를 감시
      • Cost of dropping link < Drop Threshold 이면 link drop
  • Data Delivery
    • NARADA run distance vector protocol on top of mesh
    • The per-source tree used for delivery tree are constructed from the reverse shortest path between each S and R
supporting conferencing app
Supporting Conferencing app.
  • conference app. 의 작은 그룹 크기와 지속적인 session 의 특성은 overlay design에 적합
  • framework
    • 각 overlay link 상에 Unicast congestion control
    • packet drop 정책을 사용하여 data rate를 adapt
enhancements of overlay design
Enhancements of Overlay Design
  • Optimizing Overlay for dual metric
    • latency 보다는 bandwidth(widest)에 더 우선순위를 부여
    • 같은 bandwidth를 가진 multiple path 가 있다면, lowest latency(shortest path)를 선택
  • Optimizing for dynamic metric
    • Adapt overlay trees to changes in network condition
      • Monitor bandwidth and latency of overlay links
    • Link measurements can be noisy
      • Aggressive adaptation may cause overlay instability
      • transient: do not react
      • persistent: react
    • Capture the long term performance of a link
      • Exponential smoothing, Metric discretization
experiment methodology
Experiment Methodology
  • adopt following strategy
    • Interleave experiments with various protocol schemes
    • Repeat same experiments at different time of day
    • Average results over 10 experiments
  • For each experiment
    • 모든 member들은 동시에 join
    • Single source, CBR traffic
    • Each experiment lasts for 20 minutes
mean bandwidth averaged over all receivers

Adapt to network congestion

  • Reach a stable overlay
  • Acquire network information
  • Self-organization
Mean Bandwidth averaged over all receivers
  • 처음 몇 분간 overlay는 많은 topology 변화
  • overlay의 quality를 향상시키기 위해 더 많은 정보를 획득
performance metric
Performance metric
  • Application Level Metrics
    • Bandwidth: throughput observed by each receiver
    • Latency: RTT between source and each receiver along overlay
  • Network perspective
    • resource usage
      • consumption of network resource of overlay tree
      • Overlay link RU = propagation delay
      • Tree RU = sum of link RU
    • protocol overhead
      • (total non-data traffic) / (total data traffic)
bw primary set 1 2 mbps
BW, Primary Set, 1.2 Mbps
  • Random’s poor performance: because of the inherent variability in Internet path characteristics
bw extended set 2 4 mbps
BW, Extended Set, 2.4 Mbps
  • Optimizing only for latency has poor bandwidth performance
  • no strong correlation between latency and bandwidth
rtt extended set 2 4mbps
RTT, Extended Set, 2.4Mbps
  • Optimizing only for bandwidth has poor latency performance
  • Bandwidth-Only cannot avoid poor latency links or long path length
protocol overhead
Protocol overhead
  • Results
    • Average overhead : 10~15%
    • Overhead의 약 90% 이상이 bandwidth probe 때문이다
  • Current scheme employs active probing for available bandwidth
    • Simple heuristics to eliminate unnecessary probes
adapting to network dynamic
Adapting to network dynamic
  • Primary Set, CBR traffic at 1.2 Mbps
  • parent 와 victim간에 congestion 발생
adapting to network dynamic1
Adapting to network dynamic
  • Recovery time
    • Detection time
    • Reaction time
    • Repair time
  • Detection time 이 recovery time의 가장 중요한 fraction이다
    • overlay 의 빠른 adapt : unstable을 초래할 수 있음
    • overlay 의 느린 adapt : 일시적인 시간 동안 performance penalty
outline3
Outline
  • Introduction
  • Hop By Hop Multicast
  • End System Multicast
  • Conclusion
    • Summary
    • References
summary
Summary
  • Hop By Hop Multicast
    • REUNITE
      • Recursive Unicast라는 개념을 제안
      • 기존의 Routing Protocol 보다 Scalability 향상
    • Hop By Hop Multicast
      • EXPRESS + 개선된 REUNITE
  • End System Multicast
    • dynamic 하고 heterogeneous한 Internet 환경에서 conferencing app. 이 수행될 수 있음
    • Overlay 를 구성하는데 있어서 bandwidth와 latency는 중요한 metric이다.
    • sparse 하고 작은 size의 group에 적당
references
References
  • Ion Stoica, T. S. Eugene Ng, Hui Zhang “REUNITE: A Recursive Unicast Approach to Multicast”, IEEE INFOCOM, March 2000
  • Luis Henrique M. K. Costa, Serge Fdida, Otto Carlos M. B. Duarte “Hop By Hop Multicast Routing Protocol”, ACM SIGCOMM, August 2001
  • Yang-hua Chu, Sanjay G. Rao, Hui Zhang “A Case for End System Multicast”, SIGMETRICS 2000
  • Yang-hua Chu, Sanjay G. Rao, Srinivasan Seshan, Hui Zhang “Enabling Conferencing Applications on the Internet Using an Overlay Multicast Architecture”, SIGCOMM, August 2001
references1
References
  • Chuck Semeria, Tom Maufer, “Introduction to IP Multicast Routing”, Internet-Draft, July 1997.
  • Stephen E. Deering, “Multicast Routing in Internetworks and Extended LANs”, ACM SIGCOMM 1988
ad