Data Comm. & Networks

Instructor: Ibrahim Tariq

Lecture 3

2

TCP/IP Protocol

3

TCP/IP Vs OSI Model

4

Four Level of Addresses

5

Relationship of Layers & Addresses in TCP/IP

6

The physical addresses will change from hop to hop,but the logical addresses usually remain the same.

Note

2.7

In Figure below a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link (bus topology LAN). As the figure shows, the computer with physical address 10 is the sender, and the computer with physical address 87 is the receiver.

2.8

Physical addresses

2.9

Most local-area networks use a 48-bit (6-byte) physical address written as 12 hexadecimal digits; every byte (2 hexadecimal digits) is separated by a colon, as shown below:

07:01:02:01:2C:4B

A 6-byte (12 hexadecimal digits) physical address.

2.10

Figure below shows a part of an internet with two routers connecting three LANs. Each device (computer or router) has a pair of addresses (logical and physical) for each connection. In this case, each computer is connected to only one link and therefore has only one pair of addresses. Each router, however, is connected to three networks (only two are shown in the figure). So each router has three pairs of addresses, one for each connection.

2.11

IP addresses

2.12

Figure below shows two computers communicating via the Internet. The sending computer is running three processes at this time with port addresses a, b, and c. The receiving computer is running two processes at this time with port addresses j and k. Process a in the sending computer needs to communicate with process j in the receiving computer. Note that although physical addresses change from hop to hop, logical and port addresses remain the same from the source to destination.

2.13

Figure 2.21 Port addresses

2.14

The physical addresses will change from hop to hop,but the logical addresses usually remain the same.

Note

2.15

A port address is a 16-bit address represented by one decimal number as shown.

753

A 16-bit port address represented as one single number.

2.16

The physical addresses change from hop to hop,but the logical and port addresses usually remain the same.

Note

17

Communication NetworkCommunication networks

Broadcast networksEnd nodes share a common channel (TV,

radio…)

Switched networks End nodes send to one (or more) end nodes

Packet switchingData sent in discrete portions

(the Internet)

Circuit switchingDedicated circuit per call

(telephone, ISDN)(physical)

18

Communication NetworkCommunication networks

Broadcast networksEnd nodes share a common channel (TV,

radio…)

Switched networks End nodes send to one (or more) end nodes

Packet switchingData sent in discrete portions

(the Internet)

Circuit switchingDedicated circuit per call

(telephone, ISDN)(physical)

19

Circuit switching

• A dedicated communication path (sequence of links-circuit) is established between the two end nodes through the nodes of the network

• Bandwidth: A circuit occupies a fixed capacity of each link for the entire lifetime of the connection. Capacity unused by the circuit cannot be used by other circuits.

• Latency: Data is not delayed at switches

20

Circuit switching (cnt’d)

Three phases involved in the communication process:

1. Establish the circuit

2. Transmit data

3. Terminate the circuit

If circuit not available: busy signal (congestion)

21

Time diagram of circuit switching

circuit establishment

data transmission

host 1 node 1 node 2 host 2

Delay host 1- node 1

time

Processing delay node 1

DATA

Delay host 2- host 1

switch

22

Circuit Switching

• Network resources (e.g., bandwidth) divided into “pieces”

• pieces allocated to calls• resource piece idle if not used by owning call

(no sharing)• dividing link bandwidth into “pieces”

– frequency division– time division

23

Circuit Switching: FDM and TDM

FDM

frequency

time

TDM

frequency

time

4 users

Example:

24

Assume that a voice channel occupies a bandwidth of 4 kHz. We need to combine three voice channels into a link with a bandwidth of 12 kHz, from 20 to 32 kHz. Show the configuration, using the frequency domain. Assume there are no guard bands.

SolutionWe shift (modulate) each of the three voice channels to a different bandwidth, as shown in Figure on next Slide. We use the 20- to 24-kHz bandwidth for the first channel, the 24- to 28-kHz bandwidth for the second channel, and the 28- to 32-kHz bandwidth for the third one. Then we combine them.

Example

25

Example (contd.)

26

Five channels, each with a 100-kHz bandwidth, are to be multiplexed together. What is the minimum bandwidth of the link if there is a need for a guard band of 10 kHz between the channels to prevent interference?

SolutionFor five channels, we need at least four guard bands. This means that the required bandwidth is at least

5 × 100 + 4 × 10 = 540 kHz

Example

27

Applications

• AM Radio– Band 530-1700KHz– Each AM Station needs 10KHz

• FM Radio– Band 88-108MHz– Each FM Station needs 200KHz

• TV– Each Channel needs 6MHz

• AMPS