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路由及群播協定與演算法 Routing and Multicast Protocol and Algorithm

路由及群播協定與演算法 Routing and Multicast Protocol and Algorithm. 報告人 : 吳啓鴻. OUTLINE. 何謂路由 靜態路由與動態路由 路由的演算法 網路群組管理協定 IGMP 群播樹 (Multicast Tree) 路徑選擇模式 DVMRP MOSPF PIM-DM PIM-SM CBT. 何謂路由.

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路由及群播協定與演算法 Routing and Multicast Protocol and Algorithm

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  1. 路由及群播協定與演算法Routing and Multicast Protocol and Algorithm 報告人:吳啓鴻

  2. OUTLINE • 何謂路由 • 靜態路由與動態路由 • 路由的演算法 • 網路群組管理協定 IGMP • 群播樹(Multicast Tree) • 路徑選擇模式 • DVMRP • MOSPF • PIM-DM • PIM-SM • CBT

  3. 何謂路由 • Internet是由網路與網路之間，以路由器相互連結所建構成的。為了正確的將封包給送到收信的主機，路由器必須將封包傳送到正確的方向才行，而這個要把封包送到「正確的方向」所作的處理，被稱為是選徑、尋徑或是Routing。 • 路由器會參考路由表格(Routing Table)來進行封包的轉送，將IP位址的Netid，與路由表格裡的Netid比較之後，來決定下一個應送往的路由器。

  4. 靜態路由與動態路由 • 路由表格與管理的控制表，可分為靜態路由與動態路由這二個種類 • 靜態路由指的是在路由器或是主機上設定固定的路由資訊的方法。而動態路由的情況，則是使用路由協定，自動設定路由資訊的方法。

  5. 靜態路由與動態路由

  6. 路由的演算法 • 路徑選擇所使用的演算法有各式各樣，代表性的方法有二個，一個是距離向量型(Distance-Vector) ，另外一個為連結狀態型(Link-State) 。 • 距離向量型(Distance-Vector)

  7. 路由的演算法 • 連結狀態型(Link-State)

  8. IP群播 • IP位址範圍為 224.0.0.0~239.255.255.255。 • 除了最高四個位元為1110之外，剩下的二十八個位元是用來表示Group ID。

  9. 網路群組管理協定 IGMP IGMP(Internet Group Management Protocol) 是讓主機可以加入或離開群組的協定，目前 共有三個版本︰ • IGMPv1(RFC1112) • IGMPv2(RFC2236) • IGMPv3(RFC3376)

  10. IGMPv1 IGMPv1 標頭格式

  11. 群播樹(Multicast Tree) • 群播協定使用兩種樹結構做群播 • 來源基礎樹(Source Based Tree) • DVMRP • MOSPF • PIM-DM • 群組共享樹(Group Shard tree) • CBT • PIM-SM

  12. A B D F Source distribution tree S Source Notation: (S, G) S = Source G = Group C E R R Receiver 1 Receiver 2

  13. A B D F Shared distribution tree S1 Source Notation: (*, G) * = all sources G = Group Shared Root S2 C E R R Receiver 1 Receiver 2

  14. Protocol types • Dense mode protocols • assumes dense group membership • Source distribution tree DVMRP (Distance Vector Multicast Routing Protocol) • MOSPF (Multicast OSPF) • PIM-DM (Protocol Independent Multicast, Dense Mode) • Sparse mode protocol • assumes sparse group membership • Shared distribution tree • CBT (Core Base Tree) • PIM-SM (Protocol Independent Multicast, Sparse Mode)

  15. DVMRP (1) form a source tree by exchanging metric source tree S Source DF R1 Receiver 1

  16. DVMRP (2) broadcast source tree S datagram Source DF R1 Receiver 1

  17. DVMRP (3) prune source tree S datagram Source IGMP DVMRP-Prune DF R1 Receiver 1

  18. DVMRP (4) X and Y pruned source tree S datagram Source DF X Y R1 Receiver 1

  19. DVMRP (4) New member source tree S datagram Source IGMP DVMRP-Graft DF X Y R1 R2 Receiver 1 Receiver 2

  20. DVMRP (4) New branch source tree S datagram Source IGMP DVMRP-Graft DF X Y R1 R2 Receiver 1 Receiver 2

  21. MOSPF • MOSPF (Multicast Extensions to OSPF)為 OSPF協定的延伸 • OSPF為連結狀態的路由協定。在路由器之間，交換網路的連結狀態，作成網路的拓樸資訊。然後，利用這個拓樸資訊為基礎，來作成路由表格

  22. MOSPF • 每一個在群播資料路徑上的MOSPF路由器是以傳送儲存器的內容作為它推送判斷的基礎。 • 推送儲存器項目由兩部分組成： • 區域群組資料庫(Local group database) • 最短路徑樹(shortest path tree)

  23. MOSPF • 連結狀態型的路由協定，在網路變大的情況下，用來表示連結狀態的拓樸資料庫就會變大，而造成路徑選擇資訊的困難。 • OSPF為了能夠減輕這個計算所造成的負荷，而導入了稱為Area的概念。 • 所謂的Area，是指將數個網路與數個主機，整合成群組的動作。在每個AS內，可以存在著多數的Area。

  24. Each subnetwork consists of a designated router (DR), which is responsible for sending IGMP host membership queries and listens to the IGMP host membership reports.

  25. CBT • 核心基礎樹(Core-based tree,CBT) 協定是使用一種群組共享協定，它使用核心做為樹的根。每個區域有一台核心路由器(Core router) • 樹的形成 • 由接收端傳送加入訊息(join message) ，表示要加入一個群組。此訊息經過於送出者與會合點間的所有路由器。 • 每台在其間的路由器從訊息取出所需的資訊，比如：送出者單點傳送位址、封包到達路由器的介面，然後把訊息前送給下一台路由器。 • 會合點路由器收到一群組所有成員的加入訊息後，樹就建立起來。 • 如果一路由器想要離開某一群組，它送出離開訊息，給其上游路由器。然後，上游的路由器移去到這台路由器的路徑

  26. CBT

  27. CBT • 等樹形成後，任一來源就能夠送出群播封包給群組的所有成員。

  28. PIM的介紹 • PIM 是一個架構在底層unicast路由協定上的群播路由協定。PIM-SM和其它協定最大的不同在於其採用明確加入模式(explicit join model)。群組成員首先加入一棵share tree而且可以依照需求將此樹切換成以特定發送端為root的最短路徑樹(shortest path tree, SPT)，如此可達到更有效率的群播傳輸。

  29. Dense-mode vs Sparse-mode • Dense-mode(密集模式) • 適合經常有request 需求 • 設定簡單 • 適合 LAN • Sparse-mode(稀疏模式 • 適合少量需求 • 設定較複雜 • 適合 WAN

  30. PIM-DM(1)Initial flood of data S Source A B G F C D H I E R1 R2 Receiver 1 Receiver 2

  31. PIM-DM(2)C and D Assert to DetermineForwarder for the LAN, C Wins S IGMP PIM-Assertwith its own IP address Source A B G F C D H I E R1 R2 Receiver 1 Receiver 2

  32. PIM-DM(3)I, E, G send PruneH send Join to override G’s Prune S IGMP PIM-Prune Source IGMP PIM-Join A B G F C D H I E R1 R2 Receiver 1 Receiver 2

  33. PIM-DM(4)I Gets PrunedE’s Prune is Ignored (since R1 is a receiver) S Source A B G F C D H I E R1 R2 Receiver 1 Receiver 2

  34. PIM-DM(5)New Receiver, I send Graft S IGMP PIM-Graft Source A B G F C D H I E R1 R2 Receiver 1 R3 Receiver 2 Receiver 3

  35. PIM-DM(6)new branch S IGMP PIM-Graft Source A B G F C D H I E R1 R2 Receiver 1 R3 Receiver 2 Receiver 3

  36. PIM-SM Receiver R1 Source RP A B C D

  37. PIM-SM Receiver R1 Source Register RP A B C D Source begins sending A encapsulates data in register messang and unicasts it to the RP. R1 begins receiving data

  38. PIM-SM Receiver R1 Source Register Stop RP A B Join C D RP sends joins toward the source when it starts receiving data on the source tree, a register stop is sent to A.

  39. PIM-SM Receiver R1 Source RP A B Join C Join D Receiver R2 joins group D sends join towards RP C sends join towards RP R2 receives data on RP tree Receiver R2

  40. PIM-SM Receiver R1 Source RP A B C (S,G)RP prune D (S,G) Join D sends (S,G) join towards source A begins forwarding. SPT tree exists D sends (S,G) RP Bit prune towards RP Receiver R2

  41. PIM-SM Receiver R1 Source RP A B C D R2 is receiving data on source tree, R1 is receiving data on shared (RP) tree Receiver R2

  42. PIM-SM Source RP A B C D R1 sends IGMP leave RP stops forwarding on R1 LAN RP sends (S,G) prune towards source Receiver R2

  43. Multicast In Wireless Mobile Environments

  44. Introduction • Wireless Network Categories • Introduce the issues involved in providing multicast in a mobile environment • Discuss details of proposed multicast routing protocols

  45. Wireless Network Categories • Infrastructure Wireless: base station network is connected to the wired Internet. • Ad hoc Wireless: wireless nodes communicate directly with one another.

  46. Wireless LANs (b)Ad hoc Wireless (a)Infrastructure Wireless

  47. Issues In Mobile Environments • Multicast Forwarding Algorithm • A source-based protocol like DVMRP ,DVMRP forwards multicast packets only if it receives them on the correct interface • when mobile host (MH) moves to a new domain , its interface to the multicast router changes , resulting in the packets being dropped

  48. Issues In Mobile Environments • Dense or Sparse Model Protocol • The dense mode protocols are useful if there are a lot of users and bandwidth availabilitiy is not a problem, whereas sparse mode protocols are meant for widely distributed users with limited bandwidth.

  49. Issues In Mobile Environments • Qos Provisioning • Quality of service (QoS)-based wireless multicasting is an open issue • In this section we first describe Mobile-IP based multicasting protocols

  50. Proposals for Multicast over MIP • Remote Subscription • It is the simplest way of providing multicast through Mobile IP. • In remote subscription an MH re-subscribe to the multicast group each time it moves to a new foreign network.

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