Introduction to Network-2-

Network types

Local Area Network (LAN) High speed, low error data networks

that covers small geographic area. There are different types of LAN

networks:1. Ethernet networks

2. Token-Ring Network

3. FDDI

Transmission Types

There are two types:Baseband Transmission: Uses digital signals sent over a cable without modulation Sends binary values (0s and 1s) as pulses of different voltage levels Entire bandwidth of the cable is used to transmit a single data signal Signal flow can be bi-directionalData transmission in computer

Broadband Transmission: An analog transmission technique which may use multiple

communication channels simultaneously Each data channel is represented by modulation on a particular

frequency band, for which sending or receiving equipment must be tuned

Signal flow is one-way only; two channels are necessary for computers to send/receive data

TV and Radio transmission

1-Ethernet Networks

is the most widely used LAN technology first implemented by the DIX (Digital, Intel,

Xerox) group Ethernet Networks are based on CSMA/CD

(Carrier SENSE Multiple ACCESS/ Collision Detect) Process.

Most popular network world wide. Many variation within Ethernet networks

depending upon: Topology Type of cable used

1-Ethernet Networks

All of them use Baseband transmission

1-Ethernet Networks

Gigabit Ethernet Provides a greatly increased speed and

operates over different media. Mostly used for

• high speed LAN backbone • server connectivity

Gigabit Interface Converter (GBIC) Input/output device Plugs into a Gigabit Ethernet port (slot) Links the port with the physical media used

by the network

2-Token Ring Networks

Was developed By IBM. The most highly used network

implementation; token Ring is now only second to Ethernet.

Two standards of Token Ring networks are: IBM Token Ring IEEE

The tow standards are almost identical and are compatible to each other.

2-Token Ring Networks

There are a few specification adjustment as under:

IBM Token Ring

IEEE

Topology Star/Ring No spec/Ring

Media Twisted pair

No spec

3-FDDI Networks

Fiber Distributed Data interface is a 100 Mbps Token Ring Network based on Dual Ring Topology.

Uses a Dual Ring architecture with counter rotation between each ring.

The dual ring consist of a primary and a secondary ring.

The primary ring used for data transmission , and the secondary ring remain idle.

Ethernet Frames

Data when transmitted from one system to another is divided into segments.

Further information is added to the segment and this process is called encapsulation.

Filed added before the data called header and the fields added after the data called trailer.

Heeare+Data+Trailer= Frame. The frames for Ethernet and IEEE 802.3 are

almost identical. But they have some diifrent.

destination sourceaddr length data

FCS

IEEE 802.3:

Ethernet Encapsulation :

data

FCS

46-1500 bytes

7 6 2

4

8 4

46-1500

•Preamble: tells receiving station that a frame is coming

•SOF( start of Frame): indicates the beginning of the frame.

•Destination add: network /node address of destination device

•Source add: network /node address of sending device

•Length: number of bytes of data that follow this filed.

•Type: specifies the upper-layer protocol to receive the data after Ethernet processing is complete.

•Data: packet of information

•FCS (Frame check sequence): is a cyclic redundancy check (CRC)

SOFPreamble

1 6addr

Type

2

Preambledestination source

addr6 6

addr

Connection-Oriented/Connectionless ProtocolsConnection Oriented Protocol Provides flow control and reliable data delivery

services. This protocols is achieved by the following techniques:

Acknowledgment Retransmission Sequencing Flow control

Slow compared to connectionless protocol. In TCP/IP protocol suite, the connection oriented

protocol is TCP. Examples of applications which use TCP are FTP,

HTTP, …….ect

S Rframe sent

Acknowledgment

Connection-Oriented/Connectionless Protocols

Connectionless Protocols Provides minimal service and dose not

guarantee for delivery of packets. So it is unreliable.

In TCP/IP protocol suite, the connectionless protocol is UDP( User Datagram Protocol).

UDP works faster than TCP but is unreliable. If the datagrams arrive at the destination

computer out of sequence, UDP will drop the packets.

Examples of applications which use UDP are TFTP, SNMP, …….ect

Carrier Sense Multiple Access/ Collision Detect (CSMA/CD) Ethernet LANs manage the signals on a network by a

process called CSMA/CD. Before sending data, computer listen to the network:

If it already in use, computer wait. If it not in use, computer sends its data.

A collision might occur when two stations listen for network traffic, hear none, and transmit simultaneously.

In this case, both transmissions are damaged, and the data is lost. And the computers retransmit at some later time.

CSMA/CD stations must be able to detect collision , so that they know when they must retransmit.

Signal is referred to as carrier. NIC senses the carrier and then restrains itself from

broadcasting a signal. CSMA/CD is a contention based tecnique.

LAN/ WAN Devices

RepeatersRegenerate and propagate signals

from one another.They don’t change any information

being transmitted, and they cannot filter any information.

Help to extend the distances of networks

LAN/ WAN Devices Repeaters

LAN/ WAN Devices Hubs

Hubs Serves as the center of a star topology

network. Sometimes referred to as a multiport

repeater. Or in Ethernet, a concentrator.• Provides no forwarding intelligence• Amplifies signals.• Propagates signals through the network.• Dose not filter data packets based on destination.• No path determination or switching.• Used as network concentration point.

LAN/ WAN Devices Hubs

LAN/ WAN Devices Bridges/ Switches

Bridges/ Switches Both do the same job

• Connect LAN segments.

• Reduce traffic.

• Use a table of MAC address to determine the segment on which a frame needs to be transmitted. Switches are also referred as multiport bridges.

Bridge Switch

Max number of ports-16 Max number of ports- No limit

Uses software for switching Uses Hardware –ASIC(Application Specific Interface Circuit)

Slow Faster

Low port density High port density at a lower cost

LAN/ WAN Devices Switches

Switches Enable dedicated access Eliminate collisions and increses capacity. Supports multiple conversation at the same time.

Function of a switch: Address learning Forward/ filter decision. Loop avoidance

Build and maintain MAC address tables called as content addressable Memory (CAM) automatically.

LAN/ WAN Devices Switches

LAN/ WAN Devices Switches

How Switches Operate.

LAN/ WAN Devices

Collision Domain When computers are connected to a hub, if

any tow computers send frames at the same time, they collide and data destroyed.

All computers connected to hub are said to be in the same collision domain.

Switches/Bridges segment collision domain.

LAN/ WAN Devices

Broadcast DomainWhen a broadcast is sent by a

computer to a switch or a hub, it forwarded to all ports.

Switch or Hub do not filter broadcast traffic

Routers segment Broadcast Traffic

LAN/ WAN Devices Routers

Routers used for: Routing: IS the process of determining the best path

to a destination. Switching: Once the best path is determined, the

packets are forwarded from the source to destination port.

Segmenting networks into subnets to reduce broadcast.

Interconnecting WANs links. Interconnecting different types of networks. Interconnecting different types of Media. Filtering traffic using access link.

LAN/ WAN Devices Routers

Multicast/ Unicast/ Broadcast

Unicast: Point to point communication between two

computers within a network. The destination address will be the IP

Address/ MAC Address . Unicast process

• The source addresses the packet with the destination address

• The packet is sent into the network• The network delivers the packet to the destination.

Multicast/ Unicast/ Broadcast Multicast

A single data packet is copied and sent to specific destination on the network

Multicast Process• The source addresses the packet using a

multicast address.• The packet is sent into the network.• The network copies the packet.• A copy is delivered to each destination that is

included in the multicast address.

Multicast/ Unicast/ Broadcast Broadcast

A single data packet is copied and sent from a source to all destinations on the network.

Routers don’t allow Broadcast Traffic (Flooding).

Broadcast Process:• The source addresses the packet with the

broadcast address.• The packet is sent into the network.• The network copies the packet.• The packet copies are delivered to all destinations

on the network