Internetworking - 1

Internetworking Techniques

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without prior written permission of Professor Nen-Fu Huang (E-mail: nfhuang@cs.nthu.edu.tw).

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

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Interconnect Directly

Interconnect two or more LANs directly via an internetworking unit.

區域網路 1

區域網路 2

5 6 7

1 2 3 4

Internetworking - 4

Interconnect with WAN

Connect LANs to the WAN and be part of the WAN.

區域網路 1

56

7

廣域網路

1 2 3 4

Internetworking - 5

Interconnected via WAN

LANs are interconnected via the WAN.

區域網路 1

區域網路 2

1 2 3

5 6 7

4

廣域網路

Internetworking - 6

Hierarchical Structure

區域網路

1

廣域網路

2 3

大都會網路 大都會網路

4 89

區域網路

區域網路

10 11 12 13

14 15 16 17

5

6 7

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 相同 相同

不同

不同

不同 相同 相同

不同 不同 相同

不同 不同 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

1 1

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 1

1 2

網路區段 2

3 4

訊號增益器

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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 1

1 2

區域網路 2

3 4

橋接器

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Bridges -- Examples

FE G

HC

A

B D

1橋接器 2

10BASET 網路

10BASE5 網路

1 23

4橋接器

5

LLCToken-Ring 區域網路

LLC CSMA/CD 區域網路

10BaseTx -- 10Base5

CSMA/CD -- Token Ring

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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 4

5

1 2

3

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Routers Structure工作站 A

B C

工作站 D

高層通訊協定

網路層 網路層 網路層

高層通訊協定

區域網路 1 區域網路 2

路徑器

t2

t3t4

t5 t6

t7 t8

t1

t9

t10

高層資料

N-H

D-H

t1, t10

t2, t5, t6, t9

t3, t4, t7, t8 N-H D-T

高層資料

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

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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

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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

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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

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Differences Between Bridges and Routers

Bridges RoutersOperation at Layer 2 Operation at Layer 3Protocol Independent Protocol DependentAutomatic Address Learning/Filtering Administration Required for Addre

ss,Interface and Routes

Pass MAC Multicast/Broadcast MAC M/B can be FilteredLower Cost Higher CostNo Flow/Congestion Control Flow/Congestion ControlLimited Security Complex SecurityTransparent to End Systems Non-TransparencyWell Suited for Simple/Small Networks For WAN, Larger NetworksNo Frames Segmentation/Reassembly Frames Segmentation/Reassembl

ySpanning Tree Based Routing Optimal Routing and Load Sharing Plug and Play Requires Central Administrator

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When to use Bridges ?

Locally to exploit high performance Many different network layer protocols which co-exist on t

he same LAN Have unroutable protocols Less skilled Network Management Administrator Lower cost requirements Have a single small, centralized network Want easy installation and maintenance

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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

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Router-Based Network Example

4

區域網路 1

路徑器 1

區域網路 2

區域網路 3

5

1 2

3

路徑器 2路徑器 3

D2 D3PH2 PH3

網路層

D1

PH1

應用層表達層會議層傳輸層網路層

D1 D2PH1 PH3

網路層

R1S2 25

25

R3R1 25

25

R3 25S5

25

25

D2

PH2

應用層表達層會議層傳輸層網路層

D3

PH3

應用層表達層會議層傳輸層網路層

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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)

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Fixed Routing Example

Fixed Routing Table

1 1 1

1 1 1

2 2 2

2 2 2

2

6

6

6 6 6 6 6

5 5 5 5 5 5

7

7 7 7 7

3 3 3 3 3

3

3 4 4

4 5

A B C D E F GABCDEFG

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

5 6 7

1

2 3

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

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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

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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.

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Gateway

Gateways are correspondingly more complex and more expensive to develop.

區域網路 1

網路閘門

1 2

3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)

...

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路徑器

路徑器

路徑器

廣域網路

橋接器

區域網路

區域網路

橋接器

橋接器區域網路

區域網路

區域網路