Crimping Cables

Crimping Procedure
The correct type of cable must be selected and this must be Stranded UTP for a patch cable.
A suitable length of cable is cut.
At least 2 cm of the cable sheath has to be stripped to expose the inner pairs.
Then the pair of cables has to be untwisted.
The colored wires should be placed in the correct order using the wiring diagram according to the standard colour coding or EIA/TIA standards.
The inner wires should be cut such that they are exactly the same length and just long enough to reach the RJ45 connector with the bridge positioned over the cable sheath.
The connector has to be positioned with the spring lever at the bottom.
The wires are pushed into the connector such that the copper core should be visible from the end of the connector.
The wires have to be checked to see if they are in the correct order.
The RJ45 connector is pushed into the crimping tool and the handles are squeezed.
The cables are checked to see if they are pierced and the bridge is over the cable sheath.
The same procedure is repeated for the other end of the cable.
The cable is tested using a cable tester. This is useful in identifying any crossed wires or those which do not make contact.
Crimping Cables
Wiring for a UTP patch cable
The pairs of wires in UTP cable are colored so that you can identify the same wire at each end.
Furthermore they are usually color coded by pair so that the pairs can also be identified from end to end.
Typical CAT5 UTP cables contain 4 pairs made up of a solid colour and the same solid colour striped onto a white background.
The most common colour scheme is the one that corresponds to the Electronic Industry Association/Telecommunications Industry Association's Standard 568B.

White / Orange >> White / Orange
Orange >> Orange
White / Green >> White / Green
Blue >> Blue
White / Blue >> White / Blue
Green >> Green
White / Brown >> White / Brown
Brown >> Brown
Wiring for a cross-over cable
In order to make what is commonly referred to as a 'Crossover' cable one must change the pinout connections on ONE end of the cable.
If you do it on both ends of the cable you have crossed-over the crossover and now have a straight-through cable albeit a very non-standard one.
In this case two negatives do make a positive.

White / Orange >> White / Green
Orange >> Green
White / Green >> White / Orange
Blue >> Blue
White / Blue >> White / Blue
Green >> Orange
White / Brown >> White / Brown
Brown >> Brown

Structured Wiring Systems
Structured Wiring Systems
The computer network UTP is installed in the same manner as a telephone installation.
The main components are as follows:
A network card with a socket for an RJ45 (four pair) or RJ11 (two pair) connector.
A patch cable with the appropriate connector is used to link the network card into a wall jack.
This must be a stranded cable so that it is flexible.
Since the attenuation of stranded cable is higher than solid cable the length of this cable should not exceed 32 feet.
The cabling then passes into the wiring ducts at the back of the wall outlets and is routed to the main computer room.
Solid core cables are used as it is cheaper has lower attenuation and repeated flexibility is not required.
The cable is wired into the back of a patch panel in the computer room.
Lastly a patch cable connects the port on the front of the patch panel to free port on the hub.
Here again stranded cable should be used with a maximum length of 32 feet.

Wiring Techniques
The wall outlet and the patch panel have a punch down block for each port.
The following steps have to be completed to connect the wiring to a punch down block:
As little sheath as possible (about 3cm) is removed and the pairs are untwisted only for a maximum distance of half an inch.
Note: Excessive untwisting will allow excessive crosstalk between strands and may result in problems.
The pairs are laid over the appropriate location on the punch down block and a punch tool is used to simultaneously make connection and to cut the strand to length.
There are two formats in the punch down blocks - Krone and 110.
Appropriate punch tools are required for different formats.
The Electrical Industries Association introduced the EIA 568 specification in 1991.
This standard is called the 'Commercial Building Telecommunications Wiring Standard'.
This was the first non-proprietary networking scheme for network designers and has later been revised and updated culminating in the latest version of the TIA/EIA 568A.
Note:
The usage of special types of cables for specific situations may be required in case of local fires and safety regulations.
For example the use of plenum cable above the false ceilings in an office.
This cable is designed to be fire resistant and uses Teflon coatings so it produces a minimal amount of smoke.
PVC insulation should be avoided as this produces poisonous gas when burnt.

Introduction to Topologies

To make networks you can use either of the two connections:
Point-to-point connection
It is a one to one connection where only two devices share a connection.
As there can only be two devices which can share the connection so a level of bandwidth is assured to the user.

Multipoint connection
It is connection where three or more than three computers share the connection and is also called as multi-drop connection.
The bandwidth available for each user depends upon the number of computers on the network accessing the resources and changes drastically depending on the load.
Physical and Logical Topologies
The structure or the layout of the network is called as the topology of the network.
Network Topology is divided into two types:
Physical Topology
It explains the actual physical layout of the network.
Logical Topology
It explains the logical flow of the data through the network.

Star Topology
This is a network in which each PC is connected to a central device like hubs or switches via a point-to-point link.
When a PC sends any data on the network then the central device receives the signals and sends the signals to all the PC's on network which is connected to the central device.
For example star topology is very similar to an EPABX telephone system which is used by most of the corporate companies.
Star Topology

Advantages
It is a commonly used technology and has been previously used in telephone systems.
It is very easy to configure and reconfigure the network settings.
As all the data is sent to a central device it is very easy to manage and maintain the system while at the same time making it easy to locate any problem in the network.
Any problems in the media NIC or workstation are automatically detected and isolated.


Disadvantages
As the network is depended on a central device if the device fails the whole network fails.
You need to keep a spare hub because of this single point of failure (SPOF) of the central device.
It takes up a lot of time to install because you need to install and check each connection point.
Compared to other network topologies it requires more cables.
Star Topology

Backbones
You need backbones when you want to interlink more than one hub together using a single cable.
The backbone cable needs to be capable of higher data transfer speeds than the rest of the network so that the performance of the system is maintained and does not slow down.
For example for a network made up of UTP cables you can use fiber optic cable to maintain the bandwidth as fiber optic cable supports much better transfer speeds than UTP.
It is commonly used to interlink hub situated in different floors of a building or in completely different buildings.

Cascading hubs
It is one of the commonly used methods for using multiple hubs.
The multiple hubs can be linked together by:
Twisted-pair crossover cables - Crossover cables are typically used to connect hubs together but they can also be used for directly connecting two computers together without using a hub.
Some standalone switches have a button on the hub to effect the crossover at a particular point. This allows you to connect to another switch or a hub without using a crossover cable.

Bus Topology
It is a topology in which all nodes are attached directly to the main or backbone cable in a linear method.
The bus needs to be terminated at both ends of the cable so that the signal is reflected back when it has gone through all the devices connected on the network in one direction.
In this network the signal travels in both the direction of the cable.

Advantages
It follows the common standards and is easy to install.
Compared to other network topologies it requires the least amount of network cable.
It is the cheapest of all network topologies.
It is not dependent on any one device for its functioning and works well even if only two computers are running

Disadvantages
Compared to other topologies it is relatively hard to reconfigure.
The signal quality deteriorates with increasing number of PCs thus limiting the no of PCs which can be connected to the network using this topology.
There is also a minimum length limitation of the cable used to connect the PC's otherwise it might create a bottleneck on the network.
It is difficult to troubleshoot cable problem because it can be there anywhere on the segment of the cable.
Unlike star network topology all the other networks share the same problem of media fault as start network which provides terminated network between each device and the hub.

Ring Topology
In this topology the PCs are connected in a circle in a series of point-to-point links between each device.
You can attach the computer directly to the ring or through an intermediary device like Multi-Station Access Unit (MSAU).
In this network a signal generated by one computer is passed from one device to another in a single direction and the signal is regenerated each time at each device.
This topology has been commonly implemented as IBM's token ring and Fiber Distributed Data Interface (FDDI) or Copper Distributed Data Interface (CDDI).
Ring Topology

Advantages
It uses the least amount of cable for networking after Bus Topology.
It is relatively simple to install.
You can make a fault tolerance network by using two ring systems via dual counter rotating rings.
The dual counter rotating rings allow the PCs to avoid a break in the ring.

Disadvantages
Adding or removing a device can affect the network making it difficult to reconfigure the network.
All devices will be affected by media or device failure on the network.
It is difficult to troubleshoot any problems in this topology.
Other Topology

Hybrid-star bus and star ring
You can take the advantage of two different topologies by making a hybrid topology of two different topologies.
You can see the below images to understand how two different topologies can be combined together.
Star Bus
Star Ring

Other Topology

Hierarchical or tree - stars nested with other stars
It is common to use hierarchical topology when the star network grows beyond a certain limitation.
You can see the layout of the topology after it has been put in a hierarchical format.

Mesh
It is the most commonly used topology in Wide Area Networks (WANs) and is often seen in public networks like Internet.
According to mesh network theory every device needs to have a point-to-point connection with every other device on the network.
But in practice this network is used in a hybrid approach with only the most important devices interconnected in the mesh.
This is so because it is impractical to do so in normal condition.
These networks can be used for critical applications like important servers as other computers can take over through other routes using intermediary devices if one of the servers fail.

The SMTP Protocol

Email is one of the most popular uses of the Internet and is the main reason for manyto have adopted it.
Email allows you to send a message to anyone on your own network or anywhere else in the world using the Internet.
Email software also provides options whereby a reader could read print reply to and store email.
The Format of a Email Message
An email message consists of two parts:
The first part is known as the header which includes information:
From whom the mail has been sent
From: somebody@india.com
The person/people to whom it has been sent
To: anybody@america.com
A copy of the mail can be send to as many other people as you like at the same time as you send it to the main recipient.
Just enter the full email addresses in the cc box separated by commas or semicolons.
Cc: everybody@europe.com everybody@australia.com
If copies of the email need to be sent to multiple recipients but their email addresses must not be displayed then use Blind Carbon Copy (Bcc)
Bcc: hidden@someplace.com
The subject of the message
Subject: Project confirmation
Note: Some header information is mandatory (like the ones mentioned) whereas others are optional.
The second part is known as the body and contains plain ASCII text.
The body of the message follows the header and is usually separated by a blank line.
Email messages can only transmit plain text.
There are however encoding processes that extend the functionality of email by allowing the transfer of other data like images in the form of an attachment.
After typing your message click on Send.
Electronic Mail Addresses
An email address is always in the form of 'mailbox@Domain-name' where mailbox refers to a user or other recipients (such as distribution lists) and the domain name represents the domain of which the email server is a member.
Examples of an email address could be sudhir@jetking.com where 'sudhir' is the mailbox name and 'jetking.com' is the domain name.

SMTP Protocol
The SMTP protocol specifies how mail should be delivered from one system to another.
This protocol makes the connection from the sender's server to that of the recipient and then transfers the message.
SMTP is used:
To deliver messages from the email client to the SMTP server.
To transfer messages from one SMTP server to another.
The sending SMTP server discovers the IP address of the recipient SMTP server using the domain name part of the email address.
The SMTP server is registered on the DNS using a 'mail exchanger' (MX) record.
SMTP is not used for transferring messages from the recipient's SMTP server to its email client because it requires both source and destination to be online to make a connection.
An SMTP server retries regularly before it returns a Non-Delivery Report (NDR) to the sender.
Working of SMTP
This is based on the model of communication which is a result of a user mail request.
Because of this the sender-SMTP establishes a two-way transmission channel to a receiver-SMTP.
The receiver-SMTP may be either the ultimate destination or an intermediate.
The SMTP commands are generated by the sender-SMTP and sent to the receiver-SMTP.
SMTP replies are sent from the receiver-SMTP to the sender-SMTP in response to the commands.
After the transmission channel is established the SMTP-sender sends a MAIL command indicating the sender of the mail.
When the SMTP-receiver accepts the mail for that recipient it responds with an OK reply.
In case it does not accept the mail it responds with a reply rejecting that recipient.
Post Office Protocol (POP)
SMTP delivers mail only to hosts that are currently available.
POP is therefore designed to allow the recipients to download their mail to their email client at their own convenience.
One of the most widely used methods for retrieving electronic mail from a mailbox on computing devices is called the Post Office Protocol (POP).
POP has been adopted as a standard for email exchange by virtually all Internet service providers worldwide.
A POP client like Eudora or Outlook connects via TCP to your POP server.
The POP service is different from the SMTP service but runs on the same server.
The user is authenticated by way of a username and password and your mail is downloaded accordingly onto his PC.
Sending Email
The process of sending email can be described as follows:
The email client software on the sending computer sends the message to the email server
The email server notes the recipient's address e.g. carl@prestige.com.
It then contacts a DNS server to find the IP address of the domain name which is mentioned in the address i.e. prestige.com
It then uses SMTP to deliver the message to this email server.
The delivery requires several hops.
The World Wide Web: HTTP
The World Wide Web (WWW) is made up of a huge number of servers that can be accessed by entering the correct URL address.
Hypertext and HTTP (HyperText Transfer Protocol) form the basis of this Web.
This information can be accessed in any order and from anywhere using the hyperlinks provided.
These links are contained in the document and contain the URL of another location.
A link can also refer to another document or a location within a document.

Links are not necessarily confined to information on the same site.
For example:
http://www.jetkinginfotrain.com/
This site address takes you to Jetking Institute home page.
Links to other documents are present on this page.
The link Jetking "Kal Aaj aur Kal" requests the document found at http://www.jetkinginfotrain.com/kal_aaj_kal.htm.

They can also link to sites on other servers companies and even continents.

For example
In a search engine such as Google the documents that match your search criteria are displayed as links and may be on any server anywhere in the world.
The Structure of a URL
The Uniform Resource Locator or URL as it is commonly known is used as the addressing scheme of the Internet and other browser-based application.
The URL contains all the information that is required to locate any resource.
Each URL is unique and no two different Web pages or location can share the same URL.
The URL has a fixed structure and can comprise of up to six components.
Capitalisation is important in URLs especially since many Web servers regard upper and lower case alphabets as different.
This particularly holds true in the case of UNIX servers.

TCP/IP Services

Most TCP/IP services are client-server applications that use the TCP/IP protocol as their communication mechanism.
Client-server applications are those that are based on a central server that stores information and serves requests made by clients.
The TCP/IP services are based on the application layer protocols that provide information for delivery by TCP/IP.
Some of the TCP/IP services are:
SMTP - Simple Mail Transfer Protocol
HTTP - Hyper Text Transfer Protocol
FTP - File Transfer Protocol
NNTP - Network News Transfer Protocol
SNMP - Simple Network Management Protocol