Conceptual layers of the TCT/IP services

existencetubNetworking and Communications

Oct 26, 2013 (3 years and 7 months ago)

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1

Conceptual layers of the TCT/IP services

Applications

Application services

Reliable transport service

Connectionless packet
delivery service

Network interface

Unreliable
service:

packets may be lost,
duplicated, delayed,
or delivered out of
o
rder.

The service does
not detect such
conditions and does
not inform the
sender or receiver.


Connectionless
service:

Each packet is treated independently
from all others.

Underlying protocol: (IP)

It defines:

1.

An exact format of a packet (datagram).

2.

Rou
ting the packet
s
.

3.

Rules for hosts and routers to process packets,
sending error messages, . . .

The most
fundamental
service.


2

Datagram format:


Ethernet frame containing IP datagram:



3

Basics of the TCP/IP Network Architecture

The
purpose of TCP/IP:

to provide a universal
interconnection among machines independent of the
particular networks to which they attach
.


TCP/IP Protocol family

OSI


TCP/IP


7


SMTP FTP TELNET SNMP

Web

DNS

TFTP

Appl.
protocols

6


5


4




TCP

UDP


3


IP ICMP


2


Network
-
specific protocols (Ethernet,
Token Ring, Token Bus, X.25, etc.)


1




ICMP


Internet Control Message Protocol




4



OSI and TCP/IP reference models








Application

7

Presentation

6

Session

5

Transport

4

Network

3

Data link

2

Physical

1

FTP, Telnet, DNS, …

TCP, UDP

IP, ARP, ICMP


Data link + physical

(not part of TCP/IP)

Appl. program

Appl. program

Appl.
layer

Transport

layer

Internet

layer

TCP/IP

Any type of
network


5

A client
-
server system in

TCP/IP network architecture






(Here the client and the server are


on the same LAN)


Web
client

TCP

IP

Ethernet

driver

Web
client

TCP

IP

Ethernet

driver

Application
layer

Transport

layer

Network

laye
r

Datalink

+

Physical

layers

Appl
.
protocol(http)

TCP protocol

IP protocol

Datalink+

phys. protocols

Actual flow

LAN


6




7


8

TCP protocol


Some fields of header:

1.

Destination port number.

2.

Source port number
.

3.

Checksum.



9

UDP protocol



Fields:

1.

Destination port.

2.

Source port.

3.

Length.

4.

Checksum.


10

How TCP works


1.

Connection establishment from node (host)
127.1.2.3

to node
127.1.2.8




11

How TCP works

2.

Data transmi
ssion on the established connection
(for simple character echo as in a remote login).




Three segments per each character are sent.



Ethernet frame will have at least 64 bytes,
including 20 bytes of TCP header, 20 bytes of
IP heade
r, plus one byte for character. . .


12

How TCP works

3.

Closing the connection



13

IP protocol


Some fields of the header

1.

Destination IP address.

2.

Source IP address.

3.

Destination protocol (TCP, IP, ICMP, . . .).

4.

Time to live (TTL), up to 255 hops.