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Protocol Specifications, DataProtocol Specifications, Data

Link Layer in Internet and ATMLink Layer in Internet and ATM

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Major Techniques to Model SystemsMajor Techniques to Model Systems

y Finite State Machine (FSM) and Extended

Finite State Machine (EFSM)

y Queuing model

y Petri net

y Algebraic model

y Temporal logic

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Model descriptionModel description

y PEFSM

defined as

Q - the set of the states in the protocol or communicatingsystem

I - the set of all possible input messages

O - the set of all possible output messages

C - the set of all channels used by the incoming and outgoingmessages

:Q x I

x O*Q

qo: idle state

is the set of state transitions. Each transition specifies an inputand zero, one or more outputs accompanied with a state change.

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Model description (Contd.)Model description (Contd.)

y Queuing Network (QN) consists of 6 components:

x queue(s) for incoming messages: There may be more than onequeue for each channel

x to accept incoming messages.

x service center(s) for transition execution: For each module,conceptually there is one service center to execute the firedtransitions.

x queue(s) for outgoing messages: Each channel has one queueto store the outgoing messages for transmission. More thanone channel may share a queue.

x service center(s) for transmission( i.e., channel(s)): Eachoutgoing message is transmitted through its specific channelwith respect to a transition.

x input-to-output amplifier: An incoming message may generatezero, one or more outgoing messages.

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Queuing NetworkQueuing Network

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Model description (Contd.)Model description (Contd.)

y Work-load model

defined as the set of all inputs (:i.e., programs,

data, and commands the system receives from

its environment

is a set of external variables which influence

system performance

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DATA LINK LAYER INDATA LINK LAYER IN INTERNETINTERNET

y Point-to-Point link scenarios

y Router-router leased line (PPP)

y

dial-up host-router connection (old SLIP,now PPP)

y SLIP: Not an approved Internet Standard

(incompatibilities)

y PPP: Official Internet Standard.

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PPPPPP

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PPPPPP

y Frame format similar to HDLC

y Multi-protocol encapsulation, CRC, dynamicaddress allocation possible

y key fields: flags, protocol, CRC

y Asynchronous and synchronouscommunications Possible

y Link and Network Control Protocols (LCP,NCP) for flexible control & peer-peernegotiation

y Can be mapped onto low speed (9.6Kbps)and high speed channels (SONET)

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DATA LINK LAYER INDATA LINK LAYER IN ATMATM

y Asynchronous Transfer Mode

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THANK YOU.THANK YOU.