Internetworking - 1 Internetworking Techniques  All rights reserved. No part of this publication and file may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written permission of Professor Nen-Fu Huang (

Internetworking - 2 Interconnection Techniques  Interconnect Directly  Interconnect with WAN (Wide Area Networks)  Interconnected via WAN (Wide Area Networks)  Hierarchical Structure  Internetworking Units Repeaters Bridges Routers Gateways

Internetworking - 3 Interconnect Directly  Interconnect two or more LANs directly via an internetworking unit. 區域網路 1 區域網路

Internetworking - 4 Interconnect with WAN  Connect LANs to the WAN and be part of the WAN. 區域網路 廣域網路

Internetworking - 5 Interconnected via WAN  LANs are interconnected via the WAN. 區域網路 1 區域網路 廣域網路

Internetworking - 6 Hierarchical Structure 區域網路 1 廣域網路 2 3 大都會網路 區域網路

Internetworking - 7 Internetworking Devices 網路閘門 路徑器 橋接器 訊號增益器 連結設備 通訊協定 實體層 鏈結層 網路層 以上 MAC LLC 相同 不同 相同 不同 相同 不同 相同 不同 網路閘門 路徑器 橋接器 訊號增益器 連結設備 實際網路個數 邏輯網路個數 11 1N N N N N

Internetworking - 8 Repeaters  Physical Layer devices.  Protocol Independent.  Interconnect two or more network segments (with the same type) to be a larger network segment.  Regenerates the received digital signals. Does not process the received frames. 網路區段 網路區段 訊號增益器

Internetworking - 9 Bridges  MAC Layer devices.  Protocol Independent.  Interconnect two or more LANs with different physical layers to be a logical LAN.  Each LAN can still operate independently and parallel.  Process received frames based on the MAC addresses.  Addressed Learning Function  Frames Filtering Function  Frames Forwarding Function 區域網路 區域網路 橋接器

Internetworking - 10 Bridges -- Examples F E G HC A B D 1 橋接器 2 10BASET 網路 10BASE5 網路 橋接器 5 LLC Token-Ring 區域網路 LLC CSMA/CD 區域網路 10BaseTx -- 10Base5 CSMA/CD -- Token Ring

Internetworking - 11 Bridges  LANs interconnected via multiple bridges might include several loops.  For simple network, a tree based structure is suggested. 4 區域網路 1 橋接器 1 橋接器 3 橋接器 2 區域網路 2 區域網路 3 區域網路

Internetworking - 12 Routers Structure 工作站 A B C 工作站 D 高層通訊協定 網路層 高層通訊協定 區域網路 1 區域網路 2 路徑器 t2t2 t3t3 t4t4 t5t5 t6t6 t7t7 t8t8 t1t1 t9t9 t 10 高層資料 N-H D-H t 1, t 10 t 2, t 5, t 6, t 9 t 3, t 4, t 7, t 8 N-H D-T 高層資料 鏈結層 2 實體層 2 鏈結層 1 實體層 1 鏈結層 1 實體層 1 鏈結層 2 實體層 2

Internetworking - 13 Router Characteristics  Network Layer Routing Network layer protocol dependent Filter MAC broadcast and multicast packets Easy to support mixed media Packet fragmentation and reassembly Filtering on network addresses and information Accounting  Direct Communication Between Endpoints and Routers Highly configurable and hard to get right Handle speed mismatch Congestion control and avoidance

Internetworking - 14 Router Characteristics (Continued)  Routing Protocols Interconnect layer 3 networks and exploit arbitrary topologies Determine which route to take Static routing Dynamic routing protocol support Provides reliability with alternate routes  Router Management Troubleshooting capabilities Name-Address mapping services

Internetworking - 15 Router Protocol Needs  IP ARP, RARP, ICMP, RIP, EGP, IGRP OSPF, IS-IS  DECNET  XNS and Variations NOVELL IPX BANYAN  ISO CLNS (Connectionless Network Service)  APPLETALK  OTHERS APOLLO DOMAIN PUP CHAOSNET

Internetworking - 16 Differences Between Bridges and Routers Bridges Routers Operation at Layer 2 Operation at Layer 3 Protocol IndependentProtocol Dependent Automatic Address Learning/FilteringAdministration Required for Address, Interface and Routes Pass MAC Multicast/BroadcastMAC M/B can be Filtered Lower CostHigher Cost No Flow/Congestion ControlFlow/Congestion Control Limited SecurityComplex Security Transparent to End SystemsNon-Transparency Well Suited for Simple/Small NetworksFor WAN, Larger Networks No Frames Segmentation/ReassemblyFrames Segmentation/Reassembly Spanning Tree Based RoutingOptimal Routing and Load Sharing Plug and PlayRequires Central Administrator

Internetworking - 17 When to use Bridges ?  Locally to exploit high performance  Many different network layer protocols which co-exist on the same LAN  Have unroutable protocols  Less skilled Network Management Administrator  Lower cost requirements  Have a single small, centralized network  Want easy installation and maintenance

Internetworking - 18 When to use Routers ?  Interconnect LANs over WAN (private lines, X.25)  Heterogeneous MAC layer interconnection  Heavy broadcast/multicast traffic  A few well defined, well behaved network level protocols  Skilled Network Management Administration  Need network segmentation  Better management on faults, speed mismatch

Internetworking - 19 Router-Based Network Example

Internetworking - 20 Routing  Fixed Routing Table  Dynamic Routing Table  Routing Protocols -- The protocols used between routers to exchange the routing information, such as routing tables and network status.  Internet Routing Protocols Examples RIP (Routing Information Protocol) OSPF (Open Shortest Path First)

Internetworking - 21 Fixed Routing Example  Fixed Routing Table A B C D E F G ABCDEABCDE F G 目的地區域網路 原始 區域 網路 4 區域網路 A 路徑器 1 區域網路 B 區域網路 C 區域網路 D 區域網路 E 區域網路 F 區域網路 G 路徑器 3 路徑器 4 路徑器 5 路徑器 2 路徑器 6 路徑器 7

Internetworking - 22 Fixed Routing Example 由網路 B 來 欲往 轉至 由網路 D 來 欲往 轉至 B B A A C - C A D B D - E - E - F - F A G - G A A - A B C - B B D D C B E - E B F - F B G - G B 路徑器 1 路徑選擇表 由網路 A 來 欲往 轉至 由網路 B 來 欲往 轉至 由網路 A 來 欲往 轉至 由網路 C 來 欲往 轉至 B - A A C C B A D - D A E - E A F C F - G C G - 由網路 B 來 欲往 轉至 由網路 E 來 欲往 轉至 A - A - C - B B D - C - E E D B F - F - G - G - 由網路 A 來 欲往 轉至 由網路 E 來 欲往 轉至 由網路 C 來 欲往 轉至 由網路 F 來 欲往 轉至 由網路 C 來 欲往 轉至 由網路 G 來 欲往 轉至 A - A C B - B C D - C C E - D C F F E C G - G C A - A C B - B C D - C C E - D C F - E C G G F C B - A A C - B - D - C A E E D - F - F A G - G A 路徑器 2 路徑選擇表路徑器 3 路徑選擇表 路徑器 4 路徑選擇表路徑器 5 路徑選擇表路徑器 6 路徑選擇表 路徑器 7 路徑選擇表

Internetworking - 23 Gateways  Interconnect two or more LANs with different types.  Different protocols may be used at any or all of the network layers.  The gateway handles any conversions that necessary to go from one set of protocols to the other.  Message Format Conversion Different message format Maximum message sizes Character codes  Address Translation Different addressing structure  Protocol Conversion Replace control information Message segmentation and reassembly Data flow control Error detection and recovery  Gateway offers the greatly flexibility in network interconnection.

Internetworking - 24 Gateway  Gateways are correspondingly more complex and more expensive to develop. 區域網路 1 網路閘門 區域網路 2 或廣域網路 應用層 1 表達層 1 會議層 1 傳輸層 1 網路層 1 鏈結層 1 實體層 1 應用層 2 表達層 2 會議層 2 傳輸層 2 網路層 2 鏈結層 2 實體層 2 應用層 1 表達層 1 會議層 1 傳輸層 1 網路層 1 鏈結層 1 實體層 1 應用層 2 表達層 2 會議層 2 傳輸層 2 網路層 2 鏈結層 2 實體層 2

Internetworking - 25 Inter-LAN Networks  Inter-LAN Networks can be built by directly interconnecting various LANs with bridges, routers, or gateways, depending on how similar the networks are at the various layers.  Another approach that can be used with inter-LAN networks is to use a backbone network.  A backbone network is a central network to which other networks connect. Users are not attached directly to the backbone network: They are connected to the Access networks which in turn connect to the backbone.  A backbone network requires a high bandwidth and the ability to transmit across long distances. Optical Fiber Links Microwave-Based Links  Backbone network offers several advantages: Greater processing efficiency (parallel operation) More reliable Better traffic control (Filter traffic) Optimized different networks (Different requirements)

Internetworking - 26 Backbone Network Example... 校園網路 (FDDI)... 路徑器 廣域網路 橋接器 區域網路 橋接器 區域網路