2. Protocols and Architecture

warmersafternoonNetworking and Communications

Oct 23, 2013 (3 years and 5 months ago)

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Visual Comm. Lab.

1

2. Protocols and Architecture

Prof. Sang
-
Jo Yoo

2

Contents


Protocols


OSI


TCP/IP

Protocol

Suite




Prof. Sang
-
Jo Yoo

3

1. Protocols


Terminology


system
:

computers,

terminals
..



entity

:

user

application

programs,

s/w

package

.


protocol

:

set

of

conventions

between

the

entities

involved

to

communicate

each

other
.



-

syntax

:

data

format,

coding,

and

signal

levels


-

semantics
:
control

information

for

coordination

and

error

handling


Prof. Sang
-
Jo Yoo

4

Network Software Design


Concept

of

layering


Why?


Layer

n


Gets

services

from

n
-
1


Provides

services

to

n+
1


Black

box

to

other

layers


Communicates

with

peer

layer

at

other

end


Virtual

communication

is

horizontal


Actual

is

vertical

Tanenbaum (CN)

Prof. Sang
-
Jo Yoo

5

Interfaces and Services


Terminology


Peer

entities


Service

provider/user


Service

access

point

(SAP)


Interface

Data

Unit

(IDU)


Interface

Control

Information

(ICI)


Service

Data

Unit

(SDU)


Protocol

Data

Unit

(PDU)


Service


Set

of

operations

that

is

provided

to

the

upper

layer


Protocol


Rules

for

negotiation


Tanenbaum (CN)

Prof. Sang
-
Jo Yoo

6

Service Primitives

Primitive

Meaning

Request

An

entity

requests

a

service

for

some

work

Indication

An

entity

is

to

be

informed

about

an

event

Response

An

entity

wants

to

respond

to

an

event

Conform

The

response

to

an

earlier

request

has

come

back

Host A

Host B

Connect.Request

Connect.Indication

Connect.Response

Connect.Confirm

Data.Request

Data.Indication

Disconnect.Request

Disconnect.Indication

Prof. Sang
-
Jo Yoo

7


Important

Characteristics

of

Protocols


Direct/indirect


-

point
-
to
-
point,

multipoint
-
broadcast




-

switched

network





Monolithic/structured

Network layer

Data Link Layer

Physical Layer

Addressing

Error Recovery

Prof. Sang
-
Jo Yoo

8


Symmetric/asymmetric


-

symmetric

:

uses

the

same

protocol

between

the

entities


-

asymmetric

:

server

and

client,

switch

and

end
-
terminals
...



Standard/nonstandard


-

Standard

:

X
.
25
,

HDLC,

OSI

7

Layers,




defacto

standards

(TCP/IP,

IBM

SNA

network

)


-

nonstandard

:




needs

many

kinds

of

different

protocols

and

implementations



to

communicate




Prof. Sang
-
Jo Yoo

9


Functions

of

Protocols


Segmentation/Reassembly


-

segmentation

:

breaks

the

data

from

the

upper

layer

up

into



blocks

of

some

small

size
.










IDU

PDU

SDU

segmentation

reassembly

Prof. Sang
-
Jo Yoo

10



Why we need segmentation ?




Network may only accept blocks of data up to a certain size.



Error control is more efficient with a smaller PDU.



More equitable access to shared transmission.



Receiver may need smaller buffers.


Disadvantages of segmentation.




The smaller the block, the greater the percentage overhead



Smaller blocks results in more interrupts.

Prof. Sang
-
Jo Yoo

11


Encapsulation


Addition

of

control

information(address,

error

&

protocol

control)

to

data
.


Connection

Control


-

connection
-
oriented

:

establish

a

connection

before

data

transmission,



uses

the

connection,

and

then

release

the

connection
.


-

connectionless

:

each

data

carries

the

full

destination

address,

and

routed



through

the

network

independent

of

all

the

others
.



Prof. Sang
-
Jo Yoo

12


Ordered

Delivery


-

keeps

the

data

transmission

order

which

they

were

sent
.


-

in

connection
-
oriented

transfer,

it

is

generally

required
.



-

uses

sequence

number(max

sequence

number

should

be

greater



than

max

outstanding

PDUs

at

any

time)
.



Flow

Control


-

performed

by

a

receiving

entity

to

limit

the

amount

or

rate

of

data




that

is

sent

by

a

transmitting

entity
.


-

e
.
g,

stop
-
and
-
wait

procedure
.


Error

Control


-

guards

against

loss

or

damage

of

data

and

control

information
.


-

error

detection

based

on

a

frame

check

sequence,

and

then





error

correction

or

PDU

retransmission
.


Prof. Sang
-
Jo Yoo

13


Addressing

Addressing

Level


-

network

level

address
:

TCP/IP

(IP

address),OSI(network

service

access

point)


-

application

level

address

:

TCP/IP

(port),

OSI

(service

access

point)


-

physical

level

address

:

IEEE

802
(MAC),

X
.
25
(DTE

address)

Prof. Sang
-
Jo Yoo

14

Addressing

Scope


-

Global

nonambiguity


-

Global

applicability


Connection

Identifier


-

Connection

identifier

is

used

to

identify

the

logical

connection

number




between

the

entities

in

the

connection
-
oriented

communications
.


-

During

the

data

transfer

phase,

uses

a

connection

identifier

instead

of


a

full

network

address

for

routing

and

multiplexing
.



-

e
.
g
.
,

in

case

of

ATM,

VPI/VCI

values



Transmission

Services


-

Priority

:

Priority

could

be

assigned

on

a

per
-
message

basis

or


per

connection

basis,

e
.
g
.
,

transmit

scheduling

based

on

the

priority
.


-

Grade

of

Service

:

Certain

user

services

may

need

better

quality



of

service
.


-

Security

Prof. Sang
-
Jo Yoo

15

2. OSI


History


needs

to

promote

the

interoperability

among

the

multivendor

equipments
.


started

in

1977

in

ISO

and

finished

in

1984
.


OSI

reference

model

:

ISO

7498
,

ITU
-
T

X
.
200



Model


defines

a

set

of

layers

and

delineate

the

services

performed

by

each

layer
.


partitions

functions

logically

and

manageably

small
.


not

have

so

many

layers

(reduce

overhead

procedure)
.

Prof. Sang
-
Jo Yoo

16

Prof. Sang
-
Jo Yoo

17


Standardization

Within

the

OSI

Framework


OSI

reference

model

provide

a

framework

for

standardization
.


The

model

defines,

in

general

terms,

the

functions

to

be

performed

at

each

layer

and

guides

the

standards

making

process
.


In

the

OSI

framework,

each

standard

can

be

made

independently

and

simultaneously

for

each

layer
.



Prof. Sang
-
Jo Yoo

18



Peer
-
to
-
peer protocol & service

Prof. Sang
-
Jo Yoo

19


Service

Primitives

and

Parameters


primitives

:

specify

the

function

to

be

performed
.


Parameters

:

are

used

to

pass

data

and

control

information
.


Prof. Sang
-
Jo Yoo

20


The

OSI

7

Layers

Physical

Layer


-

covers

the

physical

interface

between

devices

and

bit

passing

rules


-

includes

mechanical,electrical,

functional,

and

procedural

characteristics
.


Data

Link

Layer


-

makes

the

physical

link

reliable
.


-

performs

error

detection

and

control
.


-

e
.
g
.
,

HDLC,

LAPD

(ISDN)


Network

Layer


-

provides

for

the

transfer

of

information

between

end

systems

across




the

communication

network
.




Prof. Sang
-
Jo Yoo

21


-

in

case

of

point
-
to
-
point

connection,

there

may

be

no

need

for




a

network

layer
.


-

network

layer

of

the

node

performs

routing

and

switching
.


Prof. Sang
-
Jo Yoo

22

Transport

Layer


-

provides

a

mechanism

for

the

exchange

of

data

between

end

systems
.


-

in

case

of

connection
-
oriented

protocol,

ensures

error
-
free,




in

sequence

delivery
.


-

complexity

of

transport

layer

depends

on

the

underlying

network




reliability
.


-

ISO

:

TP
0
-
TP
4
(full

error

control

and

flow

control)



-

TCP/IP
:
TCP
(transmission

control

protocol)

or

UDP
(user

datagram

protocol)

Session

Layer


-

provides

a

mechanism

for

controlling

the

dialogue

between

applications




in

end

systems
.



-

Dialogue

discipline

:

full

duplex,

half

duplex


-

Grouping

:

define

groups

of

data

for

different

processing
.


-

Synchronization

:

uses

synchronization

point
.

Prof. Sang
-
Jo Yoo

23

Presentation

Layer


-

defines

the

format

of

the

data

to

be

exchanged

between

applications
.


-

performs

data

transformation

services(i
.
g
.
,

language

interpreter)
.


-

examples

of

services

:

data

compression,

encryption
.



Application

Layer


-

provides

a

means

for

application

programs

to

access

the

OSI



environments
.


-

contains

management

functions

and

general

purpose

applications



(file

transfer,

e
-
mail,


)


Prof. Sang
-
Jo Yoo

24

2. TCP/IP Protocol Suite


In

1980
s,

everyone

believed

that

OSI

would

come

to

dominate

commercially

over

TCP/IP
.


But,

it

was

never

happened
.


Why?


TCP/IP

enjoyed

extensive

use

prior

to

OSI
.


OSI

package

was

not

delivered

on

time
.


Internet

is

based

on

TCP/IP
.


Prof. Sang
-
Jo Yoo

25


Terminologies


Subnet
:

consists

of

all

systems

that

can

directly

communicate

with

each

other

using

homogenous

technologies


Inter
-
network

(Internet)
:

several

sub
-
networks

join

together
.


Site
:

a

collection

of

networks,

controlled

by

a

single

administrator
.


Host
:

systems

that

send

or

receive

messages
.


Router
:

systems

that

relay

those

messages

across

networks
.

Prof. Sang
-
Jo Yoo

26


The

TCP/IP

Protocol

Architecture


Network

access

protocol(e
.
g
.
,

token

ring,

Ethernet
.
)

is

used

to

connect

a

computer

to

a

subnetwork
.



IP

is

implemented

in

all

of

the

end

systems

and

routers
.


TCP

is

implemented

only

in

the

end

systems
.


Port2 at Host B

Host B

Router X

Prof. Sang
-
Jo Yoo

27


TCP/IP

Applications