1

IEX8175 RF Electronics

Avo Otstelekommunikatsiooni õppetool,

TTÜ raadio- ja sidetehnika inst.avo.ots@ttu.ee

2

circuit-switchednetworks

(e.g. telephone)

communication networks

switchednetworks

broadcastnetworks

packet-switched networks

datagram networks

(e.g. Internet)

virtual circuit-switched networks(e.g. ATM)

Networks

3

Layering

4

7

6

5

4

3

2

1 Füüsiline (ühendus)

Kanal

Võrk

Transport

Seanss

Esitlus

Rakendus Application

Presentation

Session

Transport

Network

Data link

Physical

SSL, WSP

RFC 791 IP,RFC 792 ICMP

TCP RFC 793, UDP RFC 768

WAE, HTTP, RFC821,822

ISO 8859-15

IEEE 802.11a

Cat5, RS-232D

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Lower three layers are hop-by-hop

Next two layers are end-to-end

Application

Transport

Network

Datalink

Physical

Application

Transport

Network

Datalink

Physical

Network

Datalink

Physical

Physical medium

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applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

networklink

physical

data

data

data

transport

transport

ack

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applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

networklink

physical

data

data

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datagram

applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

source destination

M

M

M

M

Ht

HtHn

HtHnHl

M

M

M

M

Ht

HtHn

HtHnHl

message

segment

frame

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Telnet FTP

packetradio

coaxial cable

fiberoptic

HTTP

HTTPTelnet FTP

packetradio

coaxial cable

fiberoptic

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• The application knows the requirements best, place functionality as high in the layer as possible

• If the application can implement a functionality correctly, implement it at a lower layer only as a performance enhancement

• Think twice before implementing a functionality that you believe that is useful to an application at a lower layer

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Töökindlus

• Solution 1: make each step reliable, and then concatenate them

• Solution 2: end-to-end check and retry

L1

L2

L1

sender receiver

L1

L2

router

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Töökindluse tagamine

• The receiver has to do the check anyway!

• Thus, full functionality can be entirely implemented at the upper layer; no need for reliability from lower layers

• Is there any need to implement reliability at lower layers?

L1

L2

L1

sender receiver

L1

L2

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Time slots

Arr

ival

rat

e

tts

T

C

Temporarilybuffered

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Protokollidhttp://www.private.org.il/tcpip_rl.html

http://www.eix.co.uk/Ethernet/

ftp://ftp.prenhall.com/pub/esm/sample_chapters/cs/stallings/index.html