Network Components

Session No.6

Network Components

Network Components

Network Components

• NIC (Network Interface Card)

• Repeater

• Hub

• Bridge

• Switch

• Router

• Gateway

• Different Network Domains

Network Components

Network Interface Card

Network Components

r NIC works in two modes:• General mode • Promiscuous mode

r In general mode, the Ethernet card of the computer will allow following types of packets:

• Packets send to the computer.• Broadcast Packet• Multicast packet and if computer is part of that

multicast group.r In promiscuous mode, the Ethernet card of the computer will

allow all the packets that it receives.

Network Interface Card

Network Components

1001 0011-1011 1011-0000 1101

Example: 00-00-E2-93-BB-0D

0000 0000-0000 0000-1110 0010

P/GG/U IEEE assigned

Vendor assigned

48 bits or 6 bytes

Manufacturer of the card

Ethernet Address Format

Network Components

Repeater

• A repeater receives a signal, regenerates it, and passes it on.

• It can regenerate and retime network signals at the bit level to allow them to travel a longer distance on the media.

Network Components

Hub

• Hubs are actually multiport repeaters.

• A typical repeater has just two ports, a hub generally has from four to twenty-four ports.

Network Components

Bridge

• There are times when it is necessary to break up a large LAN into smaller, more easily managed segments.

• The function of the bridge is to make intelligent decisions about whether or not to pass signals on to the next segment of a network.

• When a bridge receives a frame on the network, the destination MAC address is looked up in the bridge table to determine whether to filter, flood, or copy the frame onto another segment.

• If placed strategically, a bridge can greatly improve network performance.     

Network Components

Switch• A switch is sometimes described as a multiport bridge.

• Switches build the forwarding table to determine the destination of data being sent by one computer to another computer on the network.

• Switching is a technology that alleviates congestion in Ethernet LANs by reducing the traffic and increasing the bandwidth.

• Benefits of using Switch:

• Ethernet switch allows many users to communicate in parallel through the use of virtual circuits and dedicated network segments in a virtually collision-free environment. This maximizes the bandwidth available on the shared medium.

• Another benefit is that moving to a switched LAN environment is very cost effective because existing hardware and cabling can be reused.

Network Components

Switch Contd.,

Network Components

• Address learning

• Forward/filter decision

• Loop avoidance

Three Switch Functions

Network Components

• Initial MAC address table is empty

MAC address table

0260.8c01.1111

0260.8c01.2222

0260.8c01.3333

0260.8c01.4444

E0 E1

E2 E3

A B

C D

How Switches Learn Host Locations?

Network Components

• Station A sends a frame to Station C• Switch caches station A MAC address to port E0 by learning the source address

of data frames • The frame from station A to station C is flooded out to all ports except port E0

(unknown unicasts are flooded)

MAC address table

0260.8c01.1111

0260.8c01.2222

0260.8c01.3333

0260.8c01.4444

E0: 0260.8c01.1111

E0 E1

E2 E3DC

BA

How Switches Learn Host Locations

Network Components

• Station D sends a frame to station C• Switch caches station D MAC address to port E3 by learning the source Address of

data frames• The frame from station D to station C is flooded out to all ports except port E3

(unknown unicasts are flooded)

MAC address table

0260.8c01.1111

0260.8c01.2222

0260.8c01.3333

0260.8c01.4444

E0: 0260.8c01.1111E3: 0260.8c01.4444

E0 E1

E2 E3 DC

A B

How Switches Learn Host Locations

Network Components

r Station A sends a frame to station Cr Destination is known, frame is not

flooded

E0: 0260.8c01.1111E2: 0260.8c01.2222E1: 0260.8c01.3333E3: 0260.8c01.44440260.8c01.1111

0260.8c01.2222

0260.8c01.3333

0260.8c01.4444

E0 E1

E2 E3

XX DC

A B

MAC address table

How Switches Filter Frames

Network Components

• Station D sends a broadcast or multicast frame

• Broadcast and multicast frames are flooded to all ports other than the originating port

0260.8c01.1111

0260.8c01.2222

0260.8c01.3333

0260.8c01.4444

E0 E1

E2 E3 DC

A B

E0: 0260.8c01.1111E2: 0260.8c01.2222E1: 0260.8c01.3333E3: 0260.8c01.4444

MAC address table

Broadcast and Multicast Frames

Network Components

Router• While a router can be used to segment LANs, its major use is as a WAN

device.

• They operate at Layer 3 of the OSI model, making decisions based on network addresses.

• The two main functions of a router are the selection of best path for and the switching of frames to the proper interface.

• Routers accomplish this by building routing tables and exchanging network information with other routers.

Network Components

Router Contd.,

Network Components

Gateway

• A node on a network that serves as an entrance to another network.

• A network gateway is an internetworking system, a system that joins two networks together.

• In enterprises, the gateway is the computer that routes the traffic from a workstation to the outside network that is serving the Web pages. In homes, the gateway is the ISP that connects the user to the internet.

Network Components

Network Device Domains

Hub Bridge Switch Router

Collision Domains:

1 2 4 4

Broadcast Domains:

1 1 1 4

Network Components

Exercise for Participants

r Design a network by using different network components, servers and media. Design should start from ISP (Internet service provider).