KPTMAS : COMPUTER NETWORK

Networking DeviceHUB; BRIDGE; SWITCH; ROUTER

Ya’kob Abaidullah25/8/2010

TABLE OF CONTENT

Number Item Page

1 Introduction 3

1 Hub 4-5

2 Bridge 5-6

3 Switch 7-9

4 Router 10-11

5 Reference 12

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INTRODUCTION

HUB

A hub is the simplest of these devices. Any data packet coming from one port is sent to all other ports. It is then up to the receiving computer to decide if the packet is for it. Imagine packets going through a hub as messages going into a mailing list. The mail is sent out to everyone and it is up to the receiving party to decide if it is of interest. The biggest problem with hubs is their simplicity. Since every packet is sent out to every computer on the network, there is a lot of wasted transmission. This means that the network can easily become stuck @ jam. Hubs are typically used on small networks where the amount of data going across the network is never very high.

BRIDGE

A bridge goes one step up on a hub in that it looks at the destination of the packet before sending. If the destination address is not on the other side of the bridge it will not transmit the data. Somehow, the data packet is still sent all port at the same segment. A bridge only has one incoming and one outgoing port. To build on the email analogy above, the bridge is allowed to decide if the message should continue on. It reads the address bob@smith.com and decides if there is a bob@smith.com on the other side. If there isn’t, the message will not be transmitted. Bridges are typically used to separate parts of a network that do not need to communicate regularly, but still need to be connected.

SWITCH

A switch steps up on a bridge in that it has multiple ports. When a packet comes through a switch it is read to determine which computer to send the data to. This leads to increased efficiency in that packets are not going to computers that do not require them. Now the email analogy has multiple people able to send email to multiple users. The switch can decide where to send the mail based on the address. Most large networks use switches rather than hubs to connect computers within the same subnet.

ROUTER

A router is similar in a switch in that it forwards packets based on address. But, instead of the MAC address that a switch uses, a router can use the IP address. This allows the network to go across different protocols. The most common home use for routers is to share a broadband internet connection. The router has a public IP address and that address is shared with the network. When data comes through the router it is forwarded to the correct computer. This would be similar to the router being able to receive a packet as email and sending it to the user as a fax.

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HUB

FUNCTION & RESPONSIBILITY

An Ethernet hub is also known & act as active hub, network hub, repeater hub, hub or concentrator. It is a device for connecting multiple twisted pair or fiber optic Ethernet devices together and making them act as a single network segment. Hubs work at the physical layer (layer 1) of the OSI model. The device is a form of multiport repeater. Repeater hubs also participate in collision detection, forwarding a ‘jam signal’ to all ports if it detects a collision. Hubs also often come with a BNC and/or AUI connector to allow connection to legacy 10BASE2 or 10BASE5 network segments. The availability of low-priced network switches has decreases the usage of hub but they are still seen in older installations and more specialized applications.

HOW DOES HUB WORKS

Figure 1 : Hub repeats all messages to all nodes on a single LAN segment & then only the intended receiving computer will process the message.

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ADVANTAGE & DISADVANTAGE OF HUB

ADVANTAGES DISADVANTAGES

Hub is less expensive product. It will broadcast to all the ports & may jam the traffic

Can insert a protocol analyzer into a network connection.

It runs half duplex

If 10 Ports in a hub it will share bandwidth of 100 MbPs.

So each port share 10 Mbps

New technologies : Dual speed hubs

BRIDGE

FUNCTION & RESPONSIBILITY

Bridges are typically used to separate parts of a network segment that do not need to communicate regularly, but still need to be connected. Bridging is a forwarding technique used in packet-switched computer networks. Unlike routing, bridging makes no assumptions about where in a network a particular address is located. Instead, it depends on flooding and examination of source addresses in received packet headers to locate unknown devices. Once a device has been located, its location is recorded in a table where the MAC address is stored so as to preclude the need for further broadcasting. The utility of bridging is limited by its dependence on flooding, and is thus only used in local area networks. Bridging generally refers to Transparent bridging or Learning bridge operation which predominates in Ethernet. Another form of bridging, Source route bridging, was developed for token ring networks.

A network bridge connects multiple network segments at the data link layer (Layer 2) of the OSI model. In Ethernet networks, the term bridge formally means a device that behaves according to the IEEE 802.1D standard. A bridge and switch are very much alike; a switch being a bridge with numerous ports. Switch or Layer 2 switch is often used interchangeably with bridge.

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Bridges are similar to repeaters or network hubs, devices that connect network segments at the physical layer (Layer 1) of the OSI model; however, with bridging, traffic from one network is managed rather than simply rebroadcast to adjacent network segments. Bridges are more complex than hubs or repeaters. Bridges can analyze incoming data packets to determine if the bridge is able to send the given packet to another segment of the network.

HOW DOES BRIDGE WORKS

Bridges are typically used to separate parts of a network that do not need to communicate regularly, but still need to be connected

Figure 2 : Bridge able to allow or not a packet passing through another LAN segment. The packet will be block from entering another segment if the receiver is located on the same

segment. This is called Filtering.

ADVANTAGE & DISADVANTAGE OF BRIDGE

ADVANTAGES DISADVANTAGES

Self-configuring Does not limit the scope of broadcasts [broadcast domain cannot be controlled]

Simple bridges are inexpensive Does not scale to extremely large networks

Isolate collision domain Buffering and processing introduces delays

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SWITCH

Figure 3 : An actual switch

FUNCTION & RESPONSIBILITY

A network switch or switching hub is a computer networking device that connects network segments. Switches process data at the network layer (layer 3 and above) are often referred to as Layer 3 switches or multilayer switches.

The network switch, packet switch (or just switch) plays an integral part in most Ethernet local area networks or LANs. Mid-to-large sized LANs contain a number of linked managed switches. Small office/home office (SOHO) applications typically use a single switch or an all-purpose converged device such as a gateway access to small office/home broadband services such as DSL router or cable Wi-Fi router. In most of these cases, the end-user device contains a router and components that interface to the particular physical broadband technology, as in Linksys 8-port and 48-port devices. User devices may also include a telephone interface for VoIP.

A standard 10/100 Ethernet switch operates at the data-link layer of the OSI model to create a different collision domain for each switch port. If you have 4 computers (e.g., A, B, C, and D) on 4 switch ports, then A and B can transfer data back and forth, while C and D also do so simultaneously, and the two "conversations" will not interfere with one another. In the case of a "hub," they would all share the bandwidth and run in Half-duplex, resulting in collisions, which would then necessitate retransmissions. Using a switch is called microsegmentation. This allows you to have dedicated bandwidth on point-to-point connections with every computer and to therefore run in Full duplex with no collisions.

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HOW DOES SWITCH WORKS

Figure 4 : Figure shows how switch transmit data.

Data is forwarded only to the destination node.

Each port has its own collision domain.

This allows all port on the switch to operates at Full Duplex.

ADVANTAGE & DISADVANTAGE OF SWITCH

ADVANTAGES DISADVANTAGES

Collision domain is smaller because each port contains its own collision domain

Device is costly expensive

Operates at full duplex. All devices can send & receive data at the same time.

SWITCH : SOFTWARE, PROTOCOLS & TECHNOLOGIES

Traffic monitoring on a switched networkTwo popular methods that are specifically designed to allow a network analyst to monitor traffic are:

Port mirroring — the switch sends a copy of network packets to a monitoring network connection.

SMON — "Switch Monitoring" is described by RFC 2613 and is a protocol for controlling facilities such as port mirroring.

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Typical switch management features

Turn some particular port range on or off Link bandwidth and duplex settings

Priority settings for ports

MAC filtering and other types of "port security" features which prevent MAC flooding

Use of Spanning Tree Protocol

SNMP monitoring of device and link health

Port mirroring (also known as: port monitoring, spanning port, SPAN port, roving analysis port or link mode port)

Link aggregation (also known as bonding, trunking or teaming)

VLAN settings

802.1X network access control

IGMP snooping

Link aggregation allows the use of multiple ports for the same connection achieving higher data transfer rates. Creating VLANs can serve security and performance goals by reducing the size of the broadcast domain.

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ROUTER

FUNCTION & RESPONSIBILITY

A router is an electronic device that interconnects two or more computer networks across different protocols and selectively interchanges packets of data between them. Each data packet contains address information that a router can use to determine if the source and destination are on the same network, or if the data packet must be transferred from one network to another. Where multiple routers are used in a large collection of interconnected networks, the routers exchange information about target system addresses, so that each router can build up a table showing the preferred paths between any two systems on the interconnected networks.

A router is a networking device whose software and hardware are customized to the tasks of routing and forwarding information. A router has two or more network interfaces, which may be to different physical types of network (such as copper cables, fiber, or wireless) or different network standards. Each network interface is a specialized device that converts electric signals from one form to another.

The term "layer 3 switching" is used often interchangeably with the term "routing". The term switching is generally used to refer to data forwarding between two network devices that share a common network address. This is also called layer 2 switching or LAN switching.

Conceptually, a router operates in two operational planes (or sub-systems):

Control plane: where a router builds a table (called routing table) as how a packet should be forwarded through which interface, by using either statically configured statements (called static routes) or by exchanging information with other routers in the network through a dynamical routing protocol;

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Forwarding plane: where the router actually forwards traffic (called packets in IP) from ingress (incoming) interfaces to an egress (outgoing) interface that is appropriate for the destination address that the packet carries with it, by following rules derived from the routing table that has been built in the control plane.

HOW DOES ROUTER WORKS

ADVANTAGE & DISADVANTAGE OF ROUTER

ADVANTAGES DISADVANTAGES

Router limits the collision domain. Router is more expensive than Hub, Bridge & Switch.

Router can function on LAN & WAN Router only work with routable protocol.

Router can connects different media & architectures.

Routing updates consume bandwidth.

ROUTER : SOFTWARE, PROTOCOLS & TECHNOLOGIES

Routers are also used for port forwarding for private servers.

Routers that handle both IPv4 and IPv6 arguably are multiprotocol, but in a far less variable sense than a router that processed AppleTalk, DECnet, IP, and Xerox protocol

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REFERENCE

http://www.allinterview.com/showanswers/60080.html

http://en.wikipedia.org/wiki/Network_hub

http://ipt2009.wdfiles.com/local--files/func-hwrcomp-comm/Hub.JPG

http://en.labs.wikimedia.org/wiki/Network_plus_exam_cram

http://en.wikipedia.org/wiki/Network_bridge

http://en.wikipedia.org/wiki/Router

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