Network Devices Surasak Sanguanpong nguan@ku.ac.th - - PDF document

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1/16 Network Devices Surasak Sanguanpong nguan@ku.ac.th http://www.cpe.ku.ac.th/~nguan Last updated: 27 June 2002 Applied Network Research Group Department of Computer Engineering, Kasetsart University 2/16

SLIDE 1

Applied Network Research Group Department of Computer Engineering, Kasetsart University 1/16

Network Devices

Surasak Sanguanpong nguan@ku.ac.th http://www.cpe.ku.ac.th/~nguan

Last updated: 27 June 2002 Applied Network Research Group Department of Computer Engineering, Kasetsart University 2/16

Functions v.s. OSI Model

Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Router Bridge Repeater

SLIDE 2

Applied Network Research Group Department of Computer Engineering, Kasetsart University 3/16

Hub/Repeater

Attempt to forward all Frames
Error Frames will be forwarded
A hub regenerates signals; it does not an amplifier

A B C D

D D D D

A sends a frame to D

hub

The frame is repeated out all the other ports

Applied Network Research Group Department of Computer Engineering, Kasetsart University 4/16

Hub characteristics

All devices connected to hub :

share the same collision domain share the same broadcast domain

A B C D

hub

collision domain, broadcast domain

Hubs create a single collision domain and a broadcast domain

E F G H

hub

SLIDE 3

Applied Network Research Group Department of Computer Engineering, Kasetsart University 5/16

Hub Model

Deal with signaling : operate at the Physical Layer Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Repeater

Applied Network Research Group Department of Computer Engineering, Kasetsart University 6/16

Bridge operations

A B C D E F G H segment 1 segment 2 segment 3 segment 4

A to B A to C A to F

Selectively forwards frames
Error Frames will not be forwarded

Station port A 1 B 1 C 2 D 2 E 3 G 4 Forwarding Table (F and H is currently unknown)

1 2 3 4

The frame A-to-B is blocked The frame A-to-B is forwarded to port 2 The frame A-to-B is flooded to all ports Filtering Forwarding Flooding

2 1 3 4 2 1 3 4 2 1 3 4

SLIDE 4

Applied Network Research Group Department of Computer Engineering, Kasetsart University 7/16

Bridge characteristics

All devices connected to bridges share the same broadcast

domain

Networks are segmented; each segment is its own collision

domain

bridge

collision domain collision domain broadcast domain

A B C D

Applied Network Research Group Department of Computer Engineering, Kasetsart University 8/16

Bridge Model

Deal with Data Link Frame : operate at the Data Link Layer

Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Repeater Bridge

SLIDE 5

Applied Network Research Group Department of Computer Engineering, Kasetsart University 9/16

Bridge operations

Initially, the bridge’s table is empty bridge

A B C D

1 2

station port

bridge 1 2

station port

C A

A-to-C

A 1 A B C D

bridge 1 2

station port

A D

D-to-A

A 1 D 2 A B C D

bridge 1 2

station port A 1 D 2 B 1 A B C D

A B

B-to-A Station A transmits to Station C. The bridge starts building its bridging table and forward the packet. Station D transmits to Station A. The bridge forward the packet and continues building its table. Station B transmits to Station A, the bridge does not forward the frame, since A also resides on port 1

Applied Network Research Group Department of Computer Engineering, Kasetsart University 10/16

Loop in Bridge

The learning bridge concept works for any tree

(loop free) topology

Packet is infinite looping!

SLIDE 6

Applied Network Research Group Department of Computer Engineering, Kasetsart University 11/16

Loop Avoidance with algorithm

Spanning-tree algorithms disable some interfaces to break the loop

Applied Network Research Group Department of Computer Engineering, Kasetsart University 12/16

Type of bridge

Transparent Bridges

Same Topologies

Translational Bridges

Converts frame types from one topology to another For example, Ethernet to FDDI

Source Route Bridges

Token Ring Only IBM Legacy

SLIDE 7

Applied Network Research Group Department of Computer Engineering, Kasetsart University 13/16

Bridge

A B C D

The frame to B is blocked

A B C D

The frame to C is forwarded

B C C C

Applied Network Research Group Department of Computer Engineering, Kasetsart University 14/16

Router

Network is partitioned in to a small subnetwork
Each node has its own

Data Link Layer address (e.g. Ethernet MAC address) Network Layer address (e.g. IP Address)

1.2 1.3 2.2 2.3 1.1 2.1 3.1

network node 1 1,2,3 2 1,2,3 3 1 network 1 network 2

No node inside

SLIDE 8

Applied Network Research Group Department of Computer Engineering, Kasetsart University 15/16

Router characteristics

Collision domains are isolated
Broadcast domains are isolated (do not forward layer 2

broadcast)

Error Frames will not be forwarded

broadcast domain collision domain broadcast domain collision domain broadcast domain collision domain

Applied Network Research Group Department of Computer Engineering, Kasetsart University 16/16

Router

Router Model

Deal with Network Frame : operate at the Network Layer

Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Repeater Bridge