MMC Unit 8 ppt

7/28/2019 MMC Unit 8 ppt

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Enterprise network

8.1:Introduction

8.2:LANs

8.3:Ethernet / IEEE802.3

8.4:Token ring

8.5:Bridges

8.6:FDDI

8.7:High-speed LANs

8.8:LAN protocol

8.9:Multicast LAN interconnect technologies


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8.1:Introduction

PSTN

ISDN

PBX (private branch exchange)


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8.2:LANs

LANs are used to interconnect distributed

communities of end systems

To ensure the transmission bandwidth is

shared fairly between all of the attached

stations, a number of different medium

access control (MAC) methods are used.These include (CSMA/CD) and Token ring


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8.3:Ethernet / IEEE802.3

Ethernet networks and the more recentderivative IEEE802.3 are used extensively intechnical and office environment

CSMA/CD

All the stations are attached directly to the samecable/bus ,it is said to operate in a multiple access mode

The bus operates in the broadcast mode which meansthat every frames transmitted is received by all theother stations that are attached to the bus

Because of the broadcast mode ,this will result in thecontents of the two frames being corrupted and a

collision is said to have occurred


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CSMA/CD Protocol

Carrier Sense before transmission

Carrier Sense while transmission

Collision: Two or more stations transmittingsimultaneously

Backoff: Random delay after collision

Deference: Defers transmission if channel is

sensed busy Collision Window (Slot time): Round-trip

propagation delay time plus some carrier sensetime. In IEEE 802.3, this value is defined to be

51.2 us.


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CSMA/CD Collision Handling

Collision Signal is generated by Physical layer.

Jam signal (collision enforcement): To make sure

that all stations involved in the collision willdetect collision. A pattern of 32 bits.

Collision backoff and retransmission method(Truncated Binary Exponential Backoff Algorithm,

BEBA): n : number of collisions experienced (n


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CSMA/CD worse-case collision

detection


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Hub configuration principles


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IEEE 802.3 Frame Format


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8.4:Token ring

All the stations are connected together by aset of unidirectional links in the form of a

ring and all frame transmissions betweenany of the stations take place over it bycirculating the frame around the ring

Only one frame transfer can be in progressover the ring at a time

Fig 8.5


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Token ring network operation


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Token ring wiring configuration


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Token ring Frame Format


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8.5:Bridges

There are two types of bridges , the one are

used with Ethernet LANs, knows as

transparent bridges , and the others withtoken ring LANs, known as source routing

bridges.


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Bridge vs Repeater


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8.5.1:Transparent bridges

With a transparent bridge, as with a repeater,thepresence of one (or more) bridges in a routebetween two communicating stations istransparent to the two stations . All routingdecisions are made exclusively by the bridge(s)

Fig 8.12

A bridge maintains a forwarding database Bridge learning

Forwarding database to be created in advanced


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Transparent bridges(cont.)


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8.5.2:Source routing bridges

The major difference between a LAN base on

source routing bridges and one base on spanning

tree bridges is that with the latter the bridgescollectively perform the routing operation in a

way that is transparent to the end stations.

Conversely, with source routing , the end stations

perform the routing function. Fig 8.15


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Token ring Frame Format


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Example


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8.6:FDDI

FDDI is an optical fiber-based ring network thatsupports a bit rate of 100 Mbps . It can used forthe interconnection of segments spread over awider geographical area than a single building,

such as a university campus or manufacturingplant.

Fig 8.18

Use two counter-rotating rings to enhance

reliability:primary ring and secondary ring Two type of station: DAS and SAS

Fig 8.19


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Physical interface


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FDDI Frame Format


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8.7:High-speed LANs

8.7.1:Fast Ethernet

8.7.2:Switched Fast Ethernet

8.7.3:Gigabit Ethernet


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8.7.1:Fast Ethernet

Fast Ethernet was to use the same shared, half-

duplex transmission mode as Ethernet but to

obtain a*10 increase in operational bit rate over10BaseT while at the same time retaining the same

wiring systems , MAC method , and frame format.

The major technological hurdle to overcome with

Fast Ethernet was how to achieve a bit rate of100Mbps over 100m of UTP cable.

Fig 8.26


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Collision detection

Fig 8.28

Detect a collision by detecting a signal on

pair 2 while it is transmitting and , the hubdetects a collision by the presence of a

signal on pair 1


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8.7.2:Switched Fast Ethernet

In order to allow multiple access/transfers

to be in progress concurrently, two

developments have been made: Switch hub architecture

Duplex working over the circuits that connect

the stations to the hub. Fig 8.29


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8.8:LAN protocol


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8.8.1:Physical layer


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8.8.2:MAC sublayer


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8.8.3:LLC sublayer


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8.8.4:Network layer

IPX

connectionless

TCP/IP


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8.9:Multicast LAN interconnect

technologies 8.9.1:Intersite gateways

8.9.2:ISDN switched connection

8.9.3:Frame relay

8.9.4:High bit rate leased lines


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8.9.1:Intersite gateways

8 9 2 ISDN it h d ti


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8.9.2:ISDN switched connection


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8.9.3:Frame relay


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8.9.4:High bit rate leased lines

Summary


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Summary

MMC Unit 8 ppt

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