ethernet lectures

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KAYVIN L. MALAWIG JULY 9, 2011

BSIT IV

1) Different type of ethernet

- A data packet on the wire is called a frame. A frame begins with Preamble and Start Frame

Delimiter, following which each Ethernet frame features an Ethernet header featuring source and

destination MAC addresses. The middle section of the frame consists of payload data including any

headers for other protocols (e.g., Internet Protocol) carried in the frame. The frame ends with a 32-bitcyclic redundancy check, which is used to detect any corruption of data in transit.

2) Bridge, Switch, Hub And Repeater

Bridge

- is, in short, a device that is used to connect two networks together at the data link layer (layer

2 of the OSI model).

- OSI means open system interconnection

Switch- uses "intelligent" multiplexing to route packets from an entry node to a destination node.

Hub

- broadcasts the packet to the network until a destination node "takes" ownership of the packet.

//Switch & Hub are same.

Repeater

- is a device that amplifies and resends a packet of data. All energy signals suffer from attenuation,

and so a repeater is used to overcome the attenuation due to long cable/fiber runs.

3) Router VS Switch

- Router is cheaper than the switch.- Router is used to connect the (LAN)/connected computers to internet- Switch is to create network between computers.- Switches are used in Business Networks today, to connect computers, printers and servers

within a building or campus.

4) Network Protocols

HTTP (Hyper Text Transfer Protocol) is a method of transmitting the information on the web. HTTP

basically publishes and retrieves the HTTP pages on the World Wide Web. HTTP is a language that is used

to communicate between the browser and web server. The information that is transferred using HTTP

can be plain text, audio, video, images, and hypertext. HTTP is a request/response protocol between theclient and server.

POP3 (Post Office Protocol) In computing, e-mail clients such as (MS outlook, outlook express

and thunderbird) use Post office Protocol to retreive emails from the remote server over the TCP/IP

connection. Nearly all the users of the Internet service providers use POP 3 in the email clients to

retrieve the emails from the email servers. Most email applications use POP protocol.

Simple Mail Transfer Protocol is a protocol that is used to send the email messages between the

servers.


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(called "Hayes compatible") use a popular language developed by a company "Hayes

Microcomputer Products, Inc." The command ATDSX4, for example, indicates that pay

attention (AT), dial stored telephone number (DS), and then display the progress of the

call (X4).

o Intelligent Modems: Intelligent modems are also calledadvancedmodems. Thesemodems can accept new instructions and then respond to the commands while

transmitting data and information. These can be done by microprocessor chips and

internal read only memory (ROM) contained in the modem. Of course, these modems

are more expensive.

Short-Haul and Wireless Modems

o Short-Haul Modems: Short- haul modems are devices that transmit signals down thecable through any COM1 port. They sometimes are called modem eliminators, because

they do not require an external power source. They are also called line drivers that can

send data for a distance of more than one mile. This type of modem can be used within

or across several buildings in a company or a university campus.

o Wireless Modems:Wireless modems transmit the data signals through the air instead ofby using a cable. They sometimes are called a radiofrequency modem. This type of

modem is designed to work with cellular technology, and wireless local area networks.

Wireless modems are not yet perfected, but the technology is rapidly improving.

6) Different Types Of Cabling

Unshielded twisted pair cables, 22-24 gauge (UTP)

Advantages Inexpensive, may be in place in some places; familiar and simple to install.

Disadvantages Subject to interference, both internal and external; limited bandwidth, which

translates into slower transmissions. Somewhat vulnerable to security breaches; may become obsolete

quickly because of new technologies.

Shielded twisted pair cables, 22-24 (STP)

Advantages Easy installation; reasonable cost; resistance to interference; better electrical

characteristics than unshielded cables; better data security; easily terminated with modular connector.

Disadvantages May become obsolete due to technical advances; can be tapped, breaching

security.

Coaxial cables


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Advantages Familiar and fairly easy to install; better electrical characteristics (lower attenuation

and great bandwidth than shielded or unshielded cables; highly resistant to interference; generally good

data security; easy to connect.

Disadvantages May become obsolete due to technological advances; can be tapped, breaching

security.

Optical fiber cables

Advantages Top performance; excellent bandwidth ( high in the gigabit range, and theoretically

higher); very long life span; excellent security; allows for very high rates of data transmission; causes no

interference and is not subject to electromagnetic interference; smaller and lighter than other cable

types.

Disadvantages Slightly higher installed cost than twisted -pair cables.

7) Most efficient at moving packets between similar network topologies

Router is more efficient than the Bridge in terms of topologies.

8.) Type of cabling is easiest to install

UTP - Some STP cables use a thick braided shield. These cables are heavier, thicker, and harder

to install than their UTP counterparts

9) Device is transfer packets across multiple networks & use tables to store network address

to determine the best destination

Bridges is used for determining the best destination.

10) Network - is a collection of computer and devices connected together to share resources.


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ASSIGNMENT IN IT ELECTIVE 1

KAYVIN L. MALAWIG

BSIT IV

Devices Use In Networking

Network Repeater

A repeater connects two segments of your network cable. It retimes and regenerates the signals to

proper amplitudes and sends them to the other segments. When talking about, ethernet topology, you

are probably talking about using a hub as a repeater. Repeaters require a small amount of time to

regenerate the signal. This can cause a propagation delay which can affect network communication

when there are several repeaters in a row. Many network architectures limit the number of repeaters

that can be used in a row. Repeaters work only at the physical layer of the OSI network model.

Bridge

A bridge reads the outermost section of data on the data packet, to tell where the message is going. It

reduces the traffic on other network segments, since it does not send all packets. Bridges can be

programmed to reject packets from particular networks. Bridging occurs at the data link layer of the OSI

model, which means the bridge cannot read IP addresses, but only the outermost hardware address of

the packet. In our case the bridge can read the ethernet data which gives the hardware address of the

destination address, not the IP address. Bridges forward all broadcast messages. Only a special bridge

called a translation bridge will allow two networks of different architectures to be connected. Bridges

do not normally allow connection of networks with different architectures. The hardware address is

also called the MAC (media access control) address. To determine the network segment a MAC address

belongs to, bridges use one of:

y Transparent Bridging - They build a table of addresses (bridging table) as they receive packets. Ifthe address is not in the bridging table, the packet is forwarded to all segments other than the

one it came from. This type of bridge is used on ethernet networks.

y Source route bridging - The source computer provides path information inside the packet. This


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