CN

What are two reasons for using a layered structure?

1. it prevents technology from different layers to affect each other. 2-reduces complexity

Discuss two possible disadvantages of a layerd structure.

-doesent define any particular protocol, -exchange between two layers can require archtecture changes, -monolitic design can be more efficient

Explain the difference between PDU and SDU.

PDU (protocol data units) is used to exchange informaton between layers, SDU(Service data unit) is the payload section in PDU

Describe the purpose of SAPs.

application interface between the layers N+1 and N to exchange service primitives

advantages and disadvantages of OSI

generic model, supports connectionless and conection oriented services, changes at one layer do not affect the others/// dis: very complex, duplication of services in different layers, purely a theorethical model

adv and disadvn of TCP/IP

industry standard model, interoperable, scalable client=oriented architecture///// dis: not generic in nature but rather protocol dependend, not optimized for small networks, does not distinghuish phisical layers and data link layers

hamming code: how many bits can be detected and how manye can be corrected

detected: double bit errors/// corrected: al single bit errors with log(m) extra bits

Finit State Machine (FSM)

it is a mathematical model of computation, an abstract machine that can eb at exactly one out of finite state at any given time///

FSM key points

key points: fixed set of states, one state at a time, a sequence of inputs is sent to the machine, every state has a set of transitions and every transition is associated with an input and pointing to a state