复旦大学：《计算机网络 Computer Networking》课程电子教案（PPT课件讲稿）12 Inter-Domain Routing BGP（Border Gateway Protocol）

15-441 Computer Networking Inter-Domain routing BGP Border Gateway Protocol)

15-441 Computer Networking Inter-Domain Routing BGP (Border Gateway Protocol)

Review Overlay Multicast 10/5/06 ecture #12: Inter-Domain Routing 2

10/5/06 Lecture #12: Inter-Domain Routing 2 Review • Overlay Multicast

Failure of ip multicast Not widely deployed even after 15 years Use carefully -e.g, on LAn or campus, rarely over WAN Various failings Scalability of routing protocols Hard to manage Hard to implement TCP equivalent Hard to get applications to use IP Multicast without existing wide deployment Hard to get router vendors to support functionality and hard to get ISPs to configure routers to enable 10/5/06 ecture #12: Inter-Domain Routing 3

10/5/06 Lecture #12: Inter-Domain Routing 3 Failure of IP Multicast • Not widely deployed even after 15 years! • Use carefully – e.g., on LAN or campus, rarely over WAN • Various failings • Scalability of routing protocols • Hard to manage • Hard to implement TCP equivalent • Hard to get applications to use IP Multicast without existing wide deployment • Hard to get router vendors to support functionality and hard to get ISPs to configure routers to enable

Supporting Multicast on the Internet Application At which layer should multicast be implemented? P ? Network nternet architecture 10/5/06 ecture #12: Inter-Domain Routing

10/5/06 Lecture #12: Inter-Domain Routing 4 Supporting Multicast on the Internet IP Application Internet architecture Network ? ? At which layer should multicast be implemented?

IP Multicast MIT Berkeley UCSD 匚 routers CMU end systems multicast flow Highly efficient Good delay 10/5/06 ecture #12: Inter-Domain Routing

10/5/06 Lecture #12: Inter-Domain Routing 5 IP Multicast CMU Berkeley MIT UCSD routers end systems multicast flow • Highly efficient • Good delay

IP Multicast architecture Service model Hosts Host-to-router protocol (IGMP Routers Multicast routing protocols ( MOSPF, DVMRE…) 10/5/06 ecture #12: Inter-Domain Routing 6

10/5/06 Lecture #12: Inter-Domain Routing 6 IP Multicast Architecture Hosts Routers Service model Host-to-router protocol (IGMP) Multicast routing protocols (MOSPF, DVMRP,…)

Naive overlay multicast MIT1 MIT Berkeley MIT2 UCSD CMU1 CMU CMU2 10/5/06 ecture #12: Inter-Domain Routing 7

10/5/06 Lecture #12: Inter-Domain Routing 7 Naïve Overlay Multicast MIT1 MIT2 CMU1 CMU2 CMU Berkeley MIT UCSD

Smart Overlay Multicast MIT1 MIT Berkeley MIT2 UCSD CMU1 CMU CMU2 10/5/06 ecture #12: Inter-Domain Routing 8

10/5/06 Lecture #12: Inter-Domain Routing 8 Smart Overlay Multicast MIT1 MIT2 CMU1 CMU2 CMU Berkeley MIT UCSD

Benefits over P multicast Quick deployment All multicast state in end systems Computation at forwarding points simplifies support for higher level functionality MIT1 MIT Berkeley MIT2 UCSD CMU1 CMU 10/5/06 ecture #12: Inter-Domain Routing CMU2 9

10/5/06 Lecture #12: Inter-Domain Routing 9 • Quick deployment • All multicast state in end systems • Computation at forwarding points simplifies support for higher level functionality Benefits Over IP Multicast MIT1 MIT2 CMU1 CMU2 CMU Berkeley MIT UCSD

Concerns with Overlay Multicast Self-organize recipients into multicast delivery overlay tree Must be closely matched to real network topology to be efficient Performance concerns compared to P Multicast Increase in delay Bandwidth waste(packet duplication) Berkeley MIT Berkeley MIT1 UCSD MIT2 UCSD MIT2 CMU1 CMU IP Multicast CMU2 Overlay Multicast CMU2 10/5/06 ecture #12: Inter-Domain Routing 10

10/5/06 Lecture #12: Inter-Domain Routing 10 Concerns with Overlay Multicast • Self-organize recipients into multicast delivery overlay tree • Must be closely matched to real network topology to be efficient • Performance concerns compared to IP Multicast • Increase in delay • Bandwidth waste (packet duplication) MIT2 Berkeley MIT1 UCSD CMU2 CMU1 IP Multicast MIT2 Berkeley MIT1 CMU1 CMU2 UCSD Overlay Multicast