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

OSI Model Configuration

Component Or Description Layer
Gateway Services All
Bit transmission and encoding 1
Cable 1
Connector and pinot details 1
Mechanical and electrical specifications for using the media. 1
Network interface hardware 1
Network medium 1
Physical network topologies 1
Transmitting and receiving signals from the network medium 1
Bridges 2
Converts incoming 1s and 0s from the physical layer to frames 2
Converts outgoing packets from the network layer to frames 2
Identifies network cards 2
Intelligent hubs (switches) 2
Logical topology 2
Brouters 2 and 3
Fragmenting packets 3
Layer 3 switches 3
Moving data from one network to another 3
Route selection and discovery 3
Routers 3
Uses the logical network address to identify the destination network 3
Acknowledgement messages and sequences numbers 4
Breaks messages from the session layer into packet format. 4
Ensuring reliable data delivery 4
Connecting security 5
Mode for the dialog 5

Client/Server Protocols

For communicating with the network servers each workstation requires network client software.
Microsoft calls this the 'redirector' while Novell calls it the 'requester.'
styThe software intercepts instructions that are designed for the network.
It then passes them onto the card driver and to the network cable itself.
This is done through transport protocol.
Lets take a look at some examples:
A person wants to send a print job somewhere on a network.
What the client software will do is it will intercept the printing order and identifies that the print job is not for the local printer.
It will then pass on the print job to the network printer and not the local printer.
It will pass on the message to the protocol and the card driver.
This will change it into a format that the network will understand.
Redirectors/Requesters also keep a track of drive designators.
Anything that involves C: is generally recognized as Local.
Whereas anything that involves G: is passed onto the network resource.
Using an NT network as an example the redirector will know that G: is really \\servername\sharename and will pass the instruction to the destination machine.

Server message Block (SMBs)
Microsoft Windows and the OS/2 are the two operating systems that use this protocol.
This protocol is used to request files from the servers and divert them to clients.
Lets take an example of a file request using the standard NT protocol:
The workstation application requests the use of a network file resource with an SMB message.
The request is then passed over to the redirector which then passes it down through the other layers of the OSI model onto the network.
When the request reaches the server the process is reversed.
SMBs allow a machine to share its files and printers to make them available for other machines to use.

NetWare Core Protocols (NCPs)
NCPs provide a similar function to SMBs in the NetWare environment.
They function at 4 layers of the OSI model application down to Transport.
NCPs provide a group of functions that manage the interchange between client and
server.
They are responsible for performing all file and print services between clients and servers.

Service Advertising Protocol (SAP)
The NetWare environment also uses the SAP protocol.
The most important function of this protocol is service advertisement
This is performed at the Application layer of the OSI model.
Service providers like file servers and print servers broadcast a SAP packet every 60 seconds to advertise their presence on the network.
When this packet is sent it informs the client that the service is still available.
Clients may also send a service query packet to request information.

Network Client software
All network operating systems may use different protocols to manage communications between the client and the server.
In order for this to work successfully the client software also has to be different.
Taking Windows 95 as example:
The operating system has both client software for Microsoft and Novell networks as well.
In order to communicate both the client for NetWare and client for Microsoft networks have to be installed.

Adding and Removing Protocols

Different operating system will provide a specific method for installing and configuring protocols.
More often than not this takes place as a part of the setup process for the operating system.
However one can also add more protocols once the system has been fully installed.
For example in Windows OS one can always add a network device from the Control Panel.

Loading Multiple Protocols
Most modern networking systems support the installation of multiple protocols to improve networking flexibility.
The clients are using the NetBEUI protocol to communicate with the NT server.
They are using the IPX/SPX protocol to communicate with the NetWare server.
The disadvantage to this approach is the additional overhead of multiple protocols that slow the machine down.
Bindings
Sometimes some machines can have multiple protocols.
They have to try each protocol in order until a connection is established.
The order in which different protocols are tried is known as binding order.
Selecting the order is operating system specific.
However it is better that the more frequently used protocols are placed first in the binding order.
This will give us better performance.
Binding is the process of linking software components together.
This is done to provide communication.
It is also possible to bind a component to one or more components above or below it.
The course of binding takes place at the interface between each protocol in a protocol stack.
It can be summarized as the connection of a protocol to the driver for the NIC.
Microsoft NDIS (Network Driver Interface Specification) and the Novell ODI (Open Driver Interface) are used by the NIC drivers to support multiple bindings.
For example 3 different protocols can be bound to the same NIC driver.
Now if the computer has 3 NICs then each can be bound to the same protocol.

Choosing a Protocol

You can choose a particular protocol depending on following reasons:
Size of a network.
Interoperability with other systems and the Internet.
The need to route.
The client and server operating systems in use.

Scenarios
From the following real scenarios choose the appropriate protocol:
You want to install a NT network for a company that has its offices in Mumbai Pune and Nasik. It wants to host a web server and allow Internet access to all staff.
You are adding some NT server to a largely NetWare environment.
You have to install a small LAN with 8 workstations running on Windows 95 and a single NT server.
Your current network is mainly Novell but:
You plan to install some NT servers to run Exchange and SQL server.
Your WAN links are not as fast as you would like them to be.
Amongst your priorities getting the most out of performance is the top most.
Your staff also needs to access the Internet.

Other Protocols

AppleTalk
AppleTalk was developed by Apple.
AppleTalk is Apple Computers' proprietary protocol stack designed to enable Apple Macintosh computers to share files and printers in a networked environment.
It is a routable protocol and is an integral part of the Mac operating system.
Appleshare is a suite of protocols or applications that provide AppleTalk's Application layer services.
The following protocols make up Appleshare:
Appleshare File Server
Macintosh's network operating system uses Appleshare File Server to provide access to remote files.
Appleshare File Server registers users and allows those users to log in and access resources.
Appleshare Print Server
The Appleshare Print Server provides printer sharing on the network.
AppleShare PC
The AppleShare PC allows DOS workstations to access Appleshare file services.
AppleShare also provides active service advertisement and collaborative service use.
8.3 Other Protocols
Data Link Control(DLC)
DLC is a protocol designed to support access to networked printers or print servers.
It is also designed to connect to IBM mainframe computers via emulation software.
DLC however does not provide any support for any higher-level protocols and does not support routing.
This is a service provided by the Data Link layer of function defined in the Open Systems Interconnection (OSI) model for network communication.
The Data Link layer of the OSI model provides reliable data transfer across one physical link (or telecommunications path) within the network.

Overview of Transport Protocols

How DHCP works
When you start TCP/IP operations you are actually broadcasting a request for address information.
The DHCP server receives the request assigns a new address for a specific time period (called a lease period) and sends it to you together with the other required configuration information
This information is acknowledged by you and used to set up its configuration.
During the lease period the DHCP server will not reallocate the address and attempts to return the same address every time you request an address.
You extend the lease by giving subsequent requests and may send a message to the server before the lease expires telling it that it no longer needs the address so it can be released and assigned to another client on the network.
Other settings such as default gateway DNS (Domain Name System) and WINS (Windows Internet Naming Service) servers may be passed to the workstation at the same time.
IPX/SPX (NWLink)
The creators of NetWare network operating system i.e. Novell developed this Protocol.
This protocol has been derived from the Xerox Network System (XNS) which was developed by Xerox in the late 1970's.
Microsoft also has a version of this protocol called NWLink.
The Microsoft version of this protocol is fully compatible with Novel IPX/SPX.
The NetWare Protocol Suite takes its name from the two main protocols at the Network and Transport layers of the OSI model:
IPX (Internetworking Packet eXchange)
SPX (Sequential Packet eXchange)
The NetWare Protocol suite provides file print message and application services.
This architecture is server-centric because workstations make requests for file services or other services from the server.
To the user at a workstation all resources appear to be local to that workstation.
For example saving a file to a file server on the network is simply a matter of saving it to a drive F (or another mapped drive).
IPX deals with addressing route selection and an end-to-end connectivity of computers.
IPX is not suitable for certain types of network communication (where reliability of data reaching the remote machine is important) because it does not maintain a connection state (i.e. it is connectionless).
In a connectionless packet delivery system packets are simply sent to the destination and there is no confirmation of the packet reaching the destination.
In a connection oriented packet delivery system the status of the packet is known and the packet delivery is confirmed.
Most of the communication on a network including workstation connections and printing use SPX.
SPX is a transport layer protocol which provides connection-oriented packet delivery and is used when IPX datagram packet delivery is not reliable enough such as for a print server.
This protocol is concerned with addressing of machines segment development (including division and combination) and connection services (packet sequencing error control and end-to-end flow control).
NetBEUI
Pronounced net-booey NetBEUI is short for NetBIOS Enhanced User Interface.
It is an enhanced version of the NetBIOS protocol used by network operating systems such as LAN Manager LAN Server Windows for Workgroups Windows 95 and Windows NT.
NetBEUI was originally designed by IBM for their LAN Manager server and later extended by Microsoft and Novell.
NetBEUI Developed in the year 1985 by IBM for its PC networks.
NetBEUI for many years was Microsoft's preferred protocol.
It used this protocol for its LAN Manager and its early NT products.
However later versions of NT Microsoft switched to its own implementations of TCP/IP.
At first NetBIOS and NetBEUI were considered to be one.
Later however NetBIOS was separated for use with other protocols e.g. TCP/IP and IPX/SPX.
NetBIOS API however became popular later on.
This was because of its ability to provide software programmers with an easy means of accessing and utilizing network resources.

Overview of Transport Protocols

Protocol is an agreed-upon format for transmitting data between two devices i.e. it is a course of action or regulations used by networked computers to communicate with each other.
The protocol determines the following:
The type of error checking to be used
Data compression method if any
How the sending device will indicate that it has finished sending a message
How the receiving device will indicate that it has received a message
A Protocol Stack collection of protocols and the order in which they work together.
In order for flawless communication to take place both the protocols must be common.
Different protocols have different ways to operate however all of them require that certain chain of actions take place when computers communicate.
In today's world there are numerous protocols used and each of these have their own advantages and disadvantages.
More often than not certain organizations or vendors create their own protocols so particular tasks can be accomplished.
Collection of protocols are called 'a protocol suite'.
It is fairly common that several protocols are designed to work together.
The most widely used protocol suites used are.
TCP/IP
Transmission Control Protocol/Internet Protocol.
IPX/SPX
Internetwork Packet Exchange/Sequenced Packet Exchange.
NetBEUI
NetBIOS (Network Basic Input Output System) Extended User Interface.
TCP/IP
TCP/IP is the actual communication standard used by the Internet.
It was developed by the U.S department of Defense in the 70's.
This network was developed by the military so it could serve as a contingent network incase a nuclear war broke out.
The network was however given to government agencies and universities for free.
Researchers and students at the respected universities incorporated the suite into the UNIX network operating systems on their computers.
They then developed higher-level protocols for FTP (File transfer protocol) SMTP (Simple Mail Transfer Protocol) and even browsing of documents in HTTP (Hyper Text Transfer Protocol).
These applications use the 'sockets' application-programming interface (API)
TCP/IP protocol suite is being used on LANs and WANs primarily because of its vigorous nature and the increasing need to use Internet technologies.
All network software vendors now include TCP/IP within their products.
Like Linux no one owns TCP/IP and anyone can contribute towards its development.
The two part of TCP/IP are:
IP
IP's responsibility is in moving data packet from node to node.
Each of the packets is forwarded on a four-byte destination address (the IP number).
TCP
TCP's responsibility is in verifying the correct delivery of data from client to server.
It is possible that data can be lost in the intermediate network.
So TCP adds support to detect errors or lost data.
In case the data is lost it triggers retransmission until the data is correctly and completely received

Configuring TCP/IP
All TCP/IP devices must be provided with the following information.
IP Address
IP addresses are used to identify each device from one and another
The format of an IP address is 4 decimal numbers separated by periods
Example of an IP address is 202.44.122.311
An IP address identifies both the network to which the device is attached and also its identity on the network
IP addresses are mandatory for all devices
Subnet Mask
The Subnet mask is used in accordance with the IP address
It is used to determine if another device is located on a local or remote network
A subnet mask is also mandatory for all devices
Default Gateway
The default gateway is the IP address of the router to which data packets designed for remote networks should be sent
The default gateway although not necessary would limit the device to communicate only within the local network
DNS (Domain Name System) Server
One or more IP addresses may be entered to identify DNS servers
These servers provide resolution of TCP/IP host names to their IP address
They are absolutely crucial for locating resources on the Internet
WINS (Windows Internet Naming Service) Server
Microsoft NT network requires WINS server addresses to be entered
This enables it to resolve server names to their IP addresses

DHCP (Dynamic Host Configuration protocol) server may be used to automatically allocate IP addresses and other settings.
This protocol allows network administrators to manage centrally and automate the assignment of IP (Internet Protocol) configurations on a computer network.
If you are using TCP/IP protocols each computer system should have a unique IP address in order to communicate with each other.
If there's no DHCP the IP address has to be entered manually.
DHCP allows a network administrator to supervise and distribute IP addresses from a central point.

Network Card Drivers

In order for a device that is connected to a computer to work a driver is needed for it to operate.
Software (driver) that's used to manage a network card is called MAC driver.
A driver is software used by a particular hardware to communicate with the operating system.
It can be bifurcated into Vendor and Operating system.
The Vendor
Hardware components that perform the same task may have completely different methods of functioning.
Therefore they have different driver software.
The Operating system
The operating system and driver must be able to communicate.
You can locate the drivers of hardware from various sources:
A large variety of operating systems bundle drivers along with it whilst others must be installed when the hardware is added.
Most Network Card manufactures ship a disk along with their card which contains the model- specific drivers for different operating systems.
Many a times these disks have applications which install the card driver itself.
Network operating systems supply drivers for most of the commonly used cards.
Now a days incase of an upgrade the drivers are available on the manufacturers website as well.
One should always make sure that they are using the latest version of the card.
This is because the newest versions have the least bugs and always optimizes performance and reduces problems.
Operating system writers provide a generic device driver interface that the NIC manufacturers can use when writing the specific NIC driver.
All Hardware devices need to use certain computer resources in order to function:
Memory Address
DMA channel
Input/Output port (I/O port)
Interrupt ReQuest channel (IRQ)
A part of the configuration of the NIC driver involves specifying which resources are configured on the hardware.
Each network operating system specifies their own methods for installing and configuring network card drivers.
More often than not this takes place as a part of the setup process for the operating system.
However it is also possible to add drivers even after the hardware has been installed.
This is done from the 'Add New Hardware' function in the Control Panel.
Updating Network card drivers
Almost all vendors will develop new drivers for their cards.
The reason vendor's do this is because there are some performance issues with the old card.
Another reason new drivers are developed is because some conflict between the old driver and the card.
One should regularly check the vendors website constantly for updated drivers.
Another way is to browse through CompurServe and MicroHouse Technical library to be aware when new drivers are available.
You can then download these drivers.
There is absolutely no difference in upgrading a driver and installing one.
NDIS and ODI
Monolithic drivers are those that could be bound to only one protocol stack.
To achieve greater flexibility driver interfaces were designed to allow multiple protocols to be bound to multiple NICs.
The two interface drivers developed were:
Open Driver Interface (ODI)
ODI was developed by a group of networking companies Novell being a more prominent one of them.
The card drivers used with ODI are frequently called MLID drivers.
Network Driver Interface Specifications (NDIS)
NDIS was developed my Microsoft Corporation.
Both of these specifications were incompatible with each other.
However with the development and acceptance of Windows 95 as a network client the problems have greatly been reduced.

Carrier sense multiple access with collision avoidance

In computer networking, Carrier Sense Multiple Access With Collision Avoidance (CSMA/CA) is a medium access control (MAC) protocol in which:
•a carrier sensing scheme is used,
•a data station that intends to transmit sends a jam signal
•after waiting a sufficient time for all stations to receive the jam signal, the data station transmits a frame
•while transmitting, if the data station detects a jam signal from another station, it stops transmitting for a random time and then tries again.
CSMA/CA is a modification of pure Carrier Sense Multiple Access (CSMA). Collision avoidance is used to improve the performance of CSMA by attempting to reserve the network for a single transmitter. This is the function of the "jamming signal" in CSMA/CA.
Token Passing is a technique in which only the system which has the token can communicate. The token is a sort of control mechanism which gives authority to the system to communicate or use the resources of that network. Once the communication is over, the token is passed to the next candidate in a sequential manner.

Ethernet is popular because it strikes a good balance between speed, cost and ease of installation. These benefits, combined with wide acceptance in the computer marketplace and the ability to support virtually all popular network protocols, make Ethernet an ideal networking technology for most computer users today.

Carrier sense multiple access with collision detection

In computer networking, Carrier Sense Multiple Access With Collision Detection (CSMA/CD) is a network control protocol in which
a carrier sensing scheme is used and
a transmitting data station that detects another signal while transmitting a frame, stops transmitting that frame, and then waits for a random time interval (known as "backoff delay" and determined using the truncated binary exponential backoff algorithm) before trying to send that frame again.
Collision detection is used to improve CSMA performance by terminating transmission as soon as a collision is detected, and reducing the probability of a second collision on retry.

Overview of Transport Protocols

TCP/IP
TCP/IP is the actual communication standard used by the Internet.
It was developed by the U.S department of Defense in the 70's.
This network was developed by the military so it could serve as a contingent network incase a nuclear war broke out.
The network was however given to government agencies and universities for free.
Researchers and students at the respected universities incorporated the suite into the UNIX network operating systems on their computers.
They then developed higher-level protocols for FTP (File transfer protocol) SMTP (Simple Mail Transfer Protocol) and even browsing of documents in HTTP (Hyper Text Transfer Protocol).
These applications use the 'sockets' application-programming interface (API)
TCP/IP protocol suite is being used on LANs and WANs primarily because of its vigorous nature and the increasing need to use Internet technologies.
All network software vendors now include TCP/IP within their products.
Like Linux no one owns TCP/IP and anyone can contribute towards its development.

Advantages of Layer 3 Switches

It has a very simplified management configuration and installation procedure.
They are less expensive than routers.
More favoured than Routers
Unlike routers Layer 3 switches have optimized hardware to pass data as fast as Layer 2 switches.
Even then they make decisions on how to transmit traffic at Layer 3 just like a router.
A Layer 3 switch is usually faster than a router in a LAN environment because it is build on switching hardware.

Disadvantages of Layer 3 Switches

Manufacturers are marketing non-compatible proprietary devices.

Layer 3 Switches

The software-controlled routers are getting rejected while hardware implementations like routing switches are getting accepted.
The routing functionality is integrated into routing switches.
This provides routing capabilities at near switching speeds and should eliminate old technology router bottlenecks.
Layer 3 is the Network layer in the OSI model.
This layer controls the routing of messages across different networks as well as network flow and traffic management.
A standard switch normally operates from the Data Link Layer of the OSI model.
But the Layer 3 switch operates in the Network layer to perform high-speed routing functions.

Reasons why RIP is inefficient than OSPF

The routing table is broadcast instead of just the changes which can result in large and often multiple packets.
There is a maximum of 25 entries per RIP packet.
The routing tables are slow to stabilize when a change in the internetwork occurs.
Link state systems reach 'convergence' more quickly.
The routing table is broadcast at regular intervals.
It is broadcast at every 30 seconds.
This results in considerable network traffic.

Static and Dynamic Routers

Dynamic Routers
Dynamic routers are those routers which automatically find their own routes by communicating with each other.
These routers require minimal configuration.
This is because their routing tables are built and modified through these communications.
This approach is very flexible as it can quickly react to changes in the internetwork e.g. router failure or broken links.
Open Shortest Path First (OSPF)

Open Shortest Path First (OSPF) uses a 'link state' algorithm to calculate routes based on number of hops line speed traffic and cost.
TCP/IP supports OSPF.
Routers use an algorithm to send routing information to all nodes in an internetwork.
This algorithm is done by the shortest path to each node based on a topography of the Internet constructed by each node.
The routing table is also attached along with the routing information.
The advantage of this algorithm is that the updates are smaller and more frequent.
These algorithms end quickly thus preventing problems like routing loops and Count-to-Infinity thus making a stable network.
Count-to-Infinity is when routers continuously increment the jumps (hops) from one router to the next in a particular network.
The only disadvantage of this algorithm being that they require a lot of CPU time and power.
Netware Link State Protocol (NLSP)

Netware Link State Protocol (NLSP) is the equivalent of OSPF for the NetWare environment.
Routing Information Protocol (RIP)

Routing Information Protocol (RIP) uses distance vector algorithms to determine routes.
This protocol is defined by RFC 1058.
This protocol specifies how routers exchange routing table information.
Sometimes the entire table is also exchanged.
Since this is inefficient it is replaced by OSPF.

Choosing Paths

The Routing Table

The routing table contains the following information:
Addresses of all known networks.
Next router in the path to the network.
Interface of the router used to forward packets to the network.
Cost of using this path.
Incase of the existence of multiple paths to the same network the path with the lowest cost is used.
Static and Dynamic Routers

Administrators have to manually configure routes between each network when the routers do not communicate amongst themselves.
Such routers are called Static routers.
This type of configuration is however possible with only small types of routers.
It also does not provide flexibility of dynamic routing.
Its advantage is that complete control remains with the network administrator.

Network Addresses

Protocols that are routable differ from protocols that are non routable.
Routable protocols contain information in each packet relating to the network address of the source and destination nodes.
This kind of information allows a router to forward the packet to a particular network rather than a particular node.
Different protocols address networks using a variety of naming schemes.
However they rely on each network having a unique address.
Choosing Paths
A routing algorithm is used to build a routing table for forwarding packets.

They are of two types:
Non-adaptive

The choice of route has to be manually configured into router.

This is also known as 'static' routing.
Adaptive

Routing information is obtained from other routers.

Routing decisions are based on traffic levels connection speeds and number of hops or administrator-preset costs.

This is known as dynamic routing.

Features of Router

Multiple Active paths
Routers are able to keep track of multiple active paths.
They keep track of multiple active paths between any given source and destination network.
This makes it more rigid towards faults than a bridge.
This is because in a bridge multiple concurrent paths are not allowed.
Identify address
Routers work at the network layer and can access more information than a bridge.
Routers can identify source and destination network addresses within packets.
Traffic Management
Routers provide excellent traffic management using intelligent path selection.
Routers select the best route which is based on traffic loads line speeds number of hops or administrator pre set costs.
The various parameters used to determine routes for packets are known as metrics.
Sharing information
Routers can share status and routing information with other routers.
By doing this they can listen to the network and identify which connections are busy and which are not.
The routers then route network traffic avoiding slow or malfunctioning connections.
Filtering bad data
Routers do not forward any information that does not have a correct network address.
This is the reason they don't forward bad data.
Routers also filter broadcast traffic by not routing broadcast packets.
What this means is that network broadcasts do not propagate throughout the internetwork.
The broadcast storms are confined to a single subnet.
Performance
Routers perform complex tasks.
This means they are slower than bridges because they keep processing data intensively.
A router can be a dedicated box with a port to all networks.
On the other hand it can also be a NOS server with multiple interface cards.
Routers support multiple protocols however all protocols are not routable.
For example NetBEUI cannot be routed.

Routers

A router is similar to a bridge but can handle more complex types of communication between dissimilar networks.
Routers are usually employed by wide area networks which often connect networks using different communication protocols and dissimilar addressing schemes.
The routers work in the Network layer thus giving them the ability to understand the protocols being used to carry the data over the network.
Since routers can understand protocols they can use the rules to decide what to do with a specific data.
TCP/IP uses the term gateway to refer to routers.
When organizations use networks for different purposes routers are used in linking them.
A router can apply rules or filter data before accepting thus rejecting other data.
A router can be used to internetwork which can be alike or dislike.
An internetwork is composed of subnets or subnetworks which are identified by a unique network addresses.
It can route data serving one purpose over a certain set of network connections while routing other data over other connections.
The more detailed piece of data for forwards the longer that piece of data is delayed before being sent on to its destination.
The cost for acquiring highly configured routers needs faster and expensive hardware.

Features of Bridges

A network may have a number of bridges.

Generally speaking bridges cannot provide multiple paths to the same segment
This is because such an arrangement will result in data looping.
The main features of bridges are as follows.
Bridges work at the data link layer since they need to understand the MAC addresses within the frames and function in a similar manner to a switch.
Most bridges are often used to link different cable types.
Some bridges can only link segments of the same type e.g. Ethernet to Ethernet.
Fewer bridges can link network segments using different technologies.
For example linking of Ethernet and token ring.
Such bridges are known as Translation bridges or Heterogeneous bridges.

Bridge Operation

Building a Routing table
A bridge will build a routing table in memory.

When the bridge is initialized the routing table is empty.

However information is constantly being added as the bridge listens to connected segments.

The bridge can enter a particular hardware address against a port number in the routing table by examining the source hardware address on frames and noting the port that received the frame.

Entries are removed from the table after some time to ensure the information remains current.

Bridges

Bridges are devices that operate at Layer 2 of the OSI reference model.
That is why they are widely referred to as Data Link Layer devices.
They serve a simple purpose:
They analyze incoming frames make forwarding decisions based on information contained in the frames and forward the frames toward the destination.
Local and remote bridges connect LAN segments in specific areas.
A bridge consists of a computer unit two or more network interface cards connecting two types of networks.
For example one interface card might connect to an Ethernet system while the second connects to a token ring system.
These two systems speak entirely different data languages and require the bridge to translate the node address supplied by one network into an address that is recognized by the others.
The bridge uses special software that accepts data from the sending network and translates it to the language other network.
A bridge therefore extends the maximum distance of network just like a repeater.

However it can also be used to segment the network to reduce network congestion.
A vast congested network can be divided into separate segments using a bridge.
Each of these segments hence will experience far lower levels of traffic loads.
This is because the bridge passes the signal only from one segment to another if needed.
Traffic between devices on the same segment also called intrasegment traffic will not affect the other segments.
A bridge works efficiently if the traffic between devices on different segments is kept minimal.
There is a business principal called the 80:20 principal this should be followed here as well.
According to this rule a well-designed network should keep 80 % of the traffic on the same segment.
Whereas it will let the remaining 20% of traffic needing to pass to another segment.
They need to ensure clients and their associated servers are placed on the same segment whenever possible.

Building the MAC address table

Lets say a MAC address cannot be found in the MAC address table of frame addressed as a broadcast. Then the switch acts like a hub and transmits the frame out of all the ports. The switch will build the MAC address table by analyzing incoming frames for a source of MAC address. It can then also add MAC address entry against the particular port number. Entries remain in the MAC address table for a period before being flushed from the table.This will ensure that problems with the switch are not encountered when MAC addresses or network cards are changed.

Switch Operation

No Collision
A switched network isolates each port in its own collision domain.
Due to this collisions cannot take place.
This also provides the devices the facility for full duplex operations.
Devices can transmit and receive at the same time.
Interpretation of this means that twice the bandwidth is available than shared Ethernet.

Switch Operation

Switches look very similar to hubs although there is a vast difference in its functionality.
Computer A transmits a frame.
The switch receives the frame into a port buffer and obtains the destination MAC address from the Ethernet frame.
The switch uses its MAC address table to look up the port connected to the destination MAC address.
The switch uses its high-speed backplane to send the frame out on port 4 for computer B to receive by creating a temporary virtual circuit.
None of the other connected devices see any activity on the network while this takes place.
Therefore these devices are able to transmit and receive at the same time.
The port buffer holds frames until they can be processed.

Switching Hubs or Switches

A switch is a small device that joins multiple computers together at a low-level network protocol layer.
Technically switches operate at layer two (Data Link Layer) of the OSI model.
Switches look nearly identical to hubs but a switch generally contains more "intelligence" (and a slightly higher price tag) than a hub.
Unlike hubs switches are capable of inspecting the data packets as they are received determining the source and destination device of that packet and forwarding that packet appropriately. By delivering messages only to the connected device that it was intended for switches conserve network bandwidth and offer generally better performance than hubs.
Like hubs switches primarily are available for Ethernet come in a range of port configurations starting with the four- and five-port models and support 10 Mbps Ethernet 100 Mbps Ethernet or both.
Ethernet networks rely on contention-based technology for accessing the network.
Devices can only transmit data on the network when the network is free.
However when more and more devices are added to a network the amount of free time available keeps diminishing.
Also by adding more devices the problem of collision may arise.
Moving to system to a switched Ethernet system can solve the problem.
In order to do this we have to replace all the hubs with switches.
This is a very cheap option as well which is much less than what it would cost you to move to a higher bandwidth system.
If we had to move to a faster Ethernet system you would have to replace all the hubs network cards and also the media or transport.
This turns out very expensive.

Multistation Access Units (MSAUs)

MSAUs are used in IBM and similar token ring networks.
MSAUs are also known as 'wiring centers' or 'concentrators'.
These devices enable token ring networks to be physically wired like star topology.
However the logical topology of a ring will remain unchanged within the MSAU.
Computer A receives the token and removes it from the network.
Computer A places a frame addressed to computer B onto the media.
The frame is received by the MSAU at port 2.
The MSAU places the frame onto its ring.
The frame moves around the ring bypassing port 3 because no node is attached.
The frame passes out of port 4 to be examined by computer C and then returns in at port 4.
The MSAU in turn will pass the frame to the next device on the ring.
The device will pass it back to the MSAU.
This continues till every device attached to the ring has seen the frame.
Features

The MSAU uses electrical relays to allow devices to join the ring.

A device in order to keep the ring connection open must supply a voltage of at least 5 volts.

Incase due to some failure the device cannot supply the requisite voltage.

The connection ring is lost and the device can no longer see any network activity.

This feature is extremely important since the frame sent to a non-functioning device is not returned to the MSAU and results in network failure.
The ports labeled 'ring out' (RO) and 'ring in' (RI) allow MSAUs to be connected together.

This enables it to form a greater ring with many more devices attached to it.

MSAUs normally have RJ-45 connectors or less frequently IBM Data Connectors.
Token ring cards may show a device failure on system startup if they are not connected to a port on the MSAU.

Hub Types

All hubs provide us with various different facilities.

They are divided into four different groups according to these facilities.
Active
These amplify or regenerate the signal.
They also connect segments to ensure all the nodes see the signals.
They have their own power supply.

Passive
All they do is connect the network segments together.
They provide no amplification of signal of any sort.
They do not have their own power supply as well.
Passive hubs are not used in Ethernet networks.

Smart hubs
They give us the same facilities as active hubs.
However they offer us with management and monitoring capabilities.
They can also be used to locate and identify problems on the network.

hubs

A hub is a small rectangular box often constructed mainly of plastic. A hub includes a series of ports that each accept a network cable. They contain four or sometimes five ports (the fifth port being reserved for 'uplink' connections to another hub or similar device). It receives its power from an ordinary wall outlet.
A hub joins multiple computers (or other network devices) together to form a single network segment.
On this network segment all computers can communicate directly with each other.
Small hubs network four computers.
Ethernet hubs are by far the most common type but hubs for other types of networks such as USB also exist.
Larger hubs contain eight 12 16 and even 24 ports.
Hubs are also known as multiport repeaters or concentrators.
They connect various segments and act like a repeater.
This enables every segment to receive signals from any other segment.

Repeaters

Network repeaters regenerate incoming signals. On physical media like Ethernet data transmissions can only span a limited distance because the quality of the signal degrades. Repeaters attempt to preserve signal integrity and extend the distance over which data can safely travel.
The actual network devices that serve as repeaters are usually referred to by another name.
Active hubs for example are sometimes called 'multiport repeaters' but usually these are simply referred to as hubs.
Not all hubs are repeaters though.
So called passive hubs retransmit signals but do not regenerate them thus they do not perform the service of a repeater.
Higher-level devices in the OSI model like switches and routers generally do not incorporate the functions of a repeater.
Technically a repeater is a physical layer device.
Suppose data is traveling over a cable.
When the length of the cable keeps on increasing the signal keeps on decreasing.
This happens due to the process of attenuation.
The amount of attenuation depends on the type of media.
A repeater is hence used to amplify the signal and extend the maximum permissible distance for a particular media.
For example the maximum length of an Ethernet cable is 202 yards.
Connecting a repeater at one end would allow the network to be extended by another 202 yards.
Repeaters can be bifurcated into two categories.
Amplifiers
Signal regenerators
Amplifiers simply amplify the signal.
This includes amplification of any noise (disturbances).
Signal regenerators strip out the original signal which has weakened.
After that they build a new signal of the original strength and condition.
Therefore signal regenerators are preferred.
However they are more complicated devices and are slower because of that.
Features of repeaters are described under as follows:
Repeaters work at the physical layer of the OSI model.
Repeaters can connect different types of cable provided they use the same access method.
For example a repeater can connect a 10Base2 Ethernet segment using a thin cable to a 10BaseF Ethernet using a fibre optic cable.
Modular repeaters allow different modules to be selected depending on the types of media to be connected.
A repeater has no packet conversion ability.
Hence we cannot combine Ethernet and token Ring segments using a repeater.
Repeaters are intranetwork connectivity devices and so segments connected by a repeater are treated as belonging to the same network.
A repeater is the cheapest way of expanding a network but it has the least intelligence
They will amplify or rebuild any and every signal passed on to them.
They don't have ability to distinguish between erroneous packets and collisions.
They also have no ability to filter or translate packets.
Repeaters can also be used for emergency standby purposes.
One can add repeaters just so that they are sure that the signal will not weaken at any point.

In addition to learning about the switch type your service provider uses, you also need to know what Service Profile Identifiers (SPIDs) are assigned to your connection.

The ISDN carrier provides a SPID to identify the line configuration of the ISDN service.

SPIDs are a series of characters (that can look like phone numbers) that identify your network to the switch at the CO.

After you're equipment is identified, the switch links the services you ordered to the connection.

Work on standards for ISDN began in the late 1960s.

A comprehensive set of ISDN recommendations was published in 1984 and is continuously updated by the Consultative Committee for International Telegraph and Telephone (CCITT), now the International Telecommunication Union Telecommunication Standardization Sector (ITU-T).

connection point in the ISDN network

The next connection point in the ISDN network is:

Network Termination type 1 (NT1) or

Network Termination type 2 (NT2) device.

These are network-termination devices that connect the four-wire subscriber wiring to the conventional two-wire local loop.

The NT2 is a more complicated device, typically found in digital Private Branch eXchanges (PBXs), that performs Layer 2 and Layer 3 protocol services. An NT1 / 2 device also exists; it is a single device that combines the functions of an NT1 and an NT2.

In North America, the NT1 is a Customer Premises Equipment (CPE) device. In most parts of the world besides North America, the NT1 is part of the network provided by the carrier.

ISDN service providers use a variety of switch types for their ISDN services. It is important that the correct switch type is configured on the ISDN device. This information is provided by your Internet Service Provider (ISP).

The most common type in the United States is AT&T's 5ESS and Nortel's DMS-100. Services offered by carriers vary greatly from nation to nation and region to region.

Like modems, each switch type operates slightly different and have a specific set of call setup requirements. You must be aware of the switch types used at the your CO (central office).

This information is specified during router configuration so your router can place ISDN network-level calls and send data.

ISDN terminals come in two types, Type 1 or Type 2.

Specialized ISDN terminals are known as Terminal Equipment type 1 (TE1).

Non-ISDN terminals such as Data Terminal Equipment (DTE) that predate the ISDN standards are referred to as Terminal Equipment type 2 (TE2).

TE1s connect to the ISDN network through a four-wire, twisted-pair digital link.

TE2s connect to the ISDN network through a TA. The ISDN TA can be either a standalone device or a board inside the TE2.

If the TE2 is implemented as a standalone device, it connects to the TA via a standard physical-layer interface.

ISDN components include:

– terminals

– terminal adapters (TAs)

– network-termination (NT) devices

– line-termination equipment

– exchange-termination equipment

ISDN provides a faster data transfer rate than modems by using the bearer channel (B channel of 64Kbps).

With multiple B channels, ISDN offers users more bandwidth on WANs than some leased lines. For example, if you were to use two B channels, the bandwidth capability is 128Kbps because each B channel handles 64Kbps.

ISDN B channels carry voice, data and image .

ISDN can provide a clear data path over which to negotiate PPP links.

ISDN

ISDN BRI is specifically used to solve the low bandwidth problems that small offices or dial-in users have with traditional telephone dial-in services.
Telephone companies developed ISDN with the intention of creating a totally digital network. ISDN was developed to use the existing telephone wiring system, and it works very much like a telephone.
When you make a data call with ISDN, the WAN link is brought up for the duration of the call and is taken down when the call is completed.

ISDN allows digital signals to be transmitted over existing telephone wiring.
This became possible when the telephone company switches were upgraded to handle digital signals.
ISDN is generally viewed as an alternative to leased lines, which can be used for telecommuting and networking small and remote offices into LANs.

ISDN's ability to bring digital connectivity to local sites has many benefits, including the following:
ISDN can carry a variety of user traffic signals. It provides access to digital video, packet-switched data, and telephone network services.
ISDN offers much faster call setup than modem connections because it uses out-of-band (D, or delta, channel) signaling.
Some ISDN calls can be setup in less than one second.

Network Masks

Network Masks
A network mask helps you know which portion of the address identifies the network and which portion of the address identifies the node. Class A, B, and C networks have default masks, also known as natural masks, as shown here:
Class A: 255.0.0.0

Class B: 255.255.0.0

Class C: 255.255.255.0

how binary octets convert to decimal

Here is how binary octets convert to decimal:
The right most bit, or least significant bit, of an octet will hold a value of 20. The bit just to the left of that will hold a value of 21. This continues until the left-most bit, or most significant bit, which will hold a value of 27. So if all binary bits are a one, the decimal equivalent would be 255 as shown here:

1 1 1 1 1 1 1 1
128 64 32 16 8 4 2 1 (128+64+32+16+8+4+2+1=255)
Here is a sample octet conversion when not all of the bits are set to 1. 0 1 0 0 0 0 0 1 0 64 0 0 0 0 0 1 (0+64+0+0+0+0+0+1=65)
And this is sample shows an IP address represented in both binary and decimal.
10. 1. 23. 19 (decimal) 00001010.00000001.00010111.00010011 (binary)
These octets are broken down to provide an addressing scheme that can accommodate large and small networks. There are five different classes of networks, A to E. This document focuses on addressing classes A to C, since classes D and E are reserved and discussion of them is beyond the scope of this document.

IP ADDRESSING

Introduction
This document will give you basic information you will need to configure your router for routing IP, such as how addresses are broken down and how subnetting works. You will learn how to assign each interface on the router an IP address with a unique subnet. And do not worry, we will show you lots of examples to help tie everything together.
Prerequisites
Requirements
There are no specific prerequisites for this document.
Components Used
This document is not restricted to specific software and hardware versions.
Additional Information
If definitions are helpful to you, use these vocabulary terms to get you started:
· Address—The unique number ID assigned to one host or interface in a network.
· Subnet—A portion of a network sharing a particular subnet address.
· Subnet mask—A 32-bit combination used to describe which portion of an address refers to the subnet and which part refers to the host.
· Interface—A network connection.
If you have already received your legitimate address(es) from the InterNIC (Internet Network Information Center), you are ready to begin. If you are not planning on connecting to the Internet, we strongly suggest that you use reserved addresses from RFC 1918 .
Conventions
For more information on document conventions, see the Cisco Technical Tips Conventions.
Understanding IP Addresses
An IP address is an address used to uniquely identify a device on an IP network. The address is made up of 32 binary bits which can be divisible into a network portion and host portion with the help of a subnet mask. The 32 binary bits are broken into four octets (1 octet = 8 bits). Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is said to be expressed in dotted decimal format (for example, 172.16.81.100). The value in each octet ranges from 0 to 255 decimal, or 00000000 - 11111111 binary.

THE TRANSPORT LAYER - LAYER 4

The four main functions of the Transport layer are:
· Segment and assemble upper-layer applications
· Transport segments from one host to another host
· Establish and manage end-to-end operations
· Error recovery
In carrying out its duties, the Transport layer performs a range of support activities, including:
· Maintaining data integrity through flow control techniques
· Multiplexing the data from upper layer applications
· Setting up and tearing down any virtual circuits established to transport the data over the network
· Hiding any network-dependent information from the upper layers (which will only confuse them)
· Breaking down Session layer (layer 5) datagrams into segments
· Monitoring the error-free delivery of the data to its destination
· Providing for general connection management and data transfer services
· Providing for the reliable (but, not guaranteed) delivery of data
Transporting Protocols
· TCP (Transmission Control Protocol): The protocol primarily concerned with the reliable delivery of packets that requires an acknowledgement of a packet's arrival at its destination.
· UDP (User Datagram Protocol): The TCP/IP best-effort protocol that isn't concerned with the reliable delivery of packets and doesn't bother with overhead such as acknowledgments.
· SPX (Sequence Package Exchange): The Novell protocol most akin to TCP. It guarantees data delivery.
· NWLink (NetWare Link): Microsoft's version of Novell's IPX/SPX.
· ATP/NBP (AppleTalk Transaction Protocol/Name Binding Protocol): AppleTalk's data transport protocols.
· NetBIOS/NetBEUI (Network Basic Input/Output System/NetBIOS extended User Interface): Microsoft's network protocols that work together to manage communications and provide data transport services.
TCP, UDP and SPX are Transport layer protocols. Network layer protocols include IP, ICMP, and IPX.
SPX is connection-oriented and its packets are tracked through the use of a sequence number associated with each packet. A positive acknowledgment must be received from the destination device for each packet before another packet is sent. A print server is an example of an application that implements SPX.
A protocol is considered connection-oriented if it meets one of two criteria:
· Data is transmitted over a negotiated, established path, a virtual circuit, between two nodes.
· The protocol includes a process for error-recovery.
The following protocols and link types are connection-oriented:
· Frame Relay
· TCP
· SPX
· X.25
Connectionless protocols:
· IP
· IPX
· UDP Note: IP and IPX are Network layer protocols.
Layer 4 protocols that implement error recovery have the following characteristics:
· They are connection-oriented, which means they establish a connection prior to the transmission of data.
· Each PDU has header information used by the receiver to acknowledge the receipt of a packet and a system to check for errors in transmission.
· The sender requires notification of packets that have been successfully received.
You use three primary methods for error-checking. They are parity bit, check-sum, and CRC.
The three basic forms of flow control are:
· Buffering
· Congestion avoidance
· Windowing

THE TRANSPORT LAYER - LAYER 4

The four main functions of the Transport layer are:
· Segment and assemble upper-layer applications
· Transport segments from one host to another host
· Establish and manage end-to-end operations
· Error recovery
In carrying out its duties, the Transport layer performs a range of support activities, including:
· Maintaining data integrity through flow control techniques
· Multiplexing the data from upper layer applications
· Setting up and tearing down any virtual circuits established to transport the data over the network
· Hiding any network-dependent information from the upper layers (which will only confuse them)
· Breaking down Session layer (layer 5) datagrams into segments
· Monitoring the error-free delivery of the data to its destination
· Providing for general connection management and data transfer services
· Providing for the reliable (but, not guaranteed) delivery of data
Transporting Protocols
· TCP (Transmission Control Protocol): The protocol primarily concerned with the reliable delivery of packets that requires an acknowledgement of a packet's arrival at its destination.
· UDP (User Datagram Protocol): The TCP/IP best-effort protocol that isn't concerned with the reliable delivery of packets and doesn't bother with overhead such as acknowledgments.
· SPX (Sequence Package Exchange): The Novell protocol most akin to TCP. It guarantees data delivery.
· NWLink (NetWare Link): Microsoft's version of Novell's IPX/SPX.
· ATP/NBP (AppleTalk Transaction Protocol/Name Binding Protocol): AppleTalk's data transport protocols.
· NetBIOS/NetBEUI (Network Basic Input/Output System/NetBIOS extended User Interface): Microsoft's network protocols that work together to manage communications and provide data transport services.
TCP, UDP and SPX are Transport layer protocols. Network layer protocols include IP, ICMP, and IPX.
SPX is connection-oriented and its packets are tracked through the use of a sequence number associated with each packet. A positive acknowledgment must be received from the destination device for each packet before another packet is sent. A print server is an example of an application that implements SPX.
A protocol is considered connection-oriented if it meets one of two criteria:
· Data is transmitted over a negotiated, established path, a virtual circuit, between two nodes.
· The protocol includes a process for error-recovery.
The following protocols and link types are connection-oriented:
· Frame Relay
· TCP
· SPX
· X.25
Connectionless protocols:
· IP
· IPX
· UDP Note: IP and IPX are Network layer protocols.
Layer 4 protocols that implement error recovery have the following characteristics:
· They are connection-oriented, which means they establish a connection prior to the transmission of data.
· Each PDU has header information used by the receiver to acknowledge the receipt of a packet and a system to check for errors in transmission.
· The sender requires notification of packets that have been successfully received.
You use three primary methods for error-checking. They are parity bit, check-sum, and CRC.
The three basic forms of flow control are:
· Buffering
· Congestion avoidance
· Windowing

THE NETWORK LAYER - LAYER 3
The Network layer of the OSI Model basically defines logical addressing and the ways that packets are moved from source to destination on a network. The functions of the Network layer can be broken down as follows:
· Message addressing
· Path determination between source and destination nodes on different networks
· Routing messages between networks
· Controlling congestion on the subnet
· Translating logical addresses into physical addresses
Logical Address Construction
Protocol
Total Address Length
Bits in Network Portion
Bits in Host Portion
TCP/IP
32
Class A - 8Class B - 16Class C - 24
Class A - 24Class B - 16Class C - 8
IPX
80
32 or less (onlysignificant digits listed)
48 bits (MAC address)
AppleTalk
24
16 or less (indicates oneor many in cable range)
8 bits or less(cynamically assigned)





Routing protocols support routed protocols. A routing protocol is used to pass messages between routers for maintaining and updating routing tables. Examples of routing protocols are RIP, IGRP, OSPF, EIGRP. Routed protocols are used to carry end-user traffic across the internetwork. Examples of routed protocols are IP and IPX
Routing Protocol Types
Protocol
Characteristics
Examples
Distance Vector
Uses hop count; views the network from its neighbors' perspective;frequnt updates; copies its routing table to neighbors
RIP, IPX RIP, IGRP
Link State
Shortest path; common view of network; event-triggered update;LSPs (link state packets) sent to all network routers
NLSP, OSPF, IS-IS
Hybrid
Distance vector with more accurate metrics; no periodic updates;only event-triggered
IS-IS, EIGRP





IPX is a member of the IPX/SPX proprietary suite of protocols. IPX operates at the Network layer. It is connectionless and uses datagrams.
NetWare terms to memorize:
· Service Advertisement Protocol (SAP) - the NetWare propocol used to advertise (update) the services available over the network.
· Routing Information Protocol (RIP) - A distance vector routing protocol similar to RIP in TCP/IP that uses ticks, hop counts and split horizon metrics.
· NetWare Link Services Protocol (NLSP) - A link state routing protocol that is the default routing protocol on NetWare 4.11 and higher.
· Novell Directory Service (NDS) - Novell's Directory Service protocol.
· NetWare Core Protocol (NCP) - Providing client-to-server connections and applications.
Configuring the router for use with the Novell NetWare IPX protocfol is a two-setp process:
Enabling IPX routing: This is done in global configuration mode. You may also enable load sharing if you want.
Assigning networks to interfaces: This step in the process assigns network numbers to each interface. Remember that multiple network numbers can be assigned as long as each uses a different encapsulation (frame) type. To apply an encapsulation type, you need to use a Cisco keyword and not the Novell frame type's name.
Novell IPX Frame Types and Cisco Keywords:
Interface
Novell Frame Type
Cisco Keyword
Ethernet
Ethernet_802.3
novell-ether (default)
Ethernet_802.2

sap
Ethernet_II

arpa
Ethernet_SNAP
:
snap
Token Ring
Token-Ring
sap (default)
FDDI
Fddi_snap
snap (default)

THE DATA LINK LAYER - LAYER 2

The Data Link layer performs a number of separate activities, including:
· Physical addressing
· Network topoloty
· Error notification
· Access to the physical medium
· Flow control
Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control.

OSI MODEL

THE APPLICATION LAYER - LAYER 7

The Application layer provides three basic services to applications:
It makes sure the resources needed to carry out a session are present.
It matches the application to the appropriate communication protocol or service.
It synchronizes the tgransmission of data between the application and its protocol.
The Application layer is used to support the following services:
File services - store, move control access to, and retrieve files
Print services - send data to local or network printers
Message services - transfer text, graphics, audio, and video over a network
Application services - process applications locally or through distributed processing
Database services - allow a local computer to access network services
In addition, the Application layer advertises any services that are being offered and determines whether requests made by the client should be processed locally or remotely (through another network resource).
The Application layer services and protocols you should know are:
· FTP (File Transfer Protocol)
· E-mail clients
· Web Browsers
· Telnet
· SNMP (Simple Network Management Protocol)
· BBS (bulletin board system) services
· EDI (Electronic Data Interchange) and other transaction services


THE PRESENTATION LAYER - LAYER 6

The main function of the presentation layer is to define the data formats used to provide a number of services to the Application layer.
Included in these services the ones you need to know are:
· Data encryption - coding data so that it is protected from unauthorizaed access
· Data compression - reducing the number of packets required for transport
· Data formatting
· Data conversion
Conversions standards defined on the Presentation Layer for data conversion and formatting:
Category
Standards


Data Conversion
ASCII, EBCDIC, encryption


Audio/video conversion
MIDI, MPEG, QuickTime, AVI


Graphics conversion
GIF, JPEG, PICT, TIFF


THE SESSION LAYER - LAYER 5

Layer 5 of the OSI model is the Session Layer, which establishes, manages, and terminates sessions between applications.
Following are some of the communication tasks performed at this layer:
Establishing connections
Maintaining connections
Synchronizing communications
Controlling dialogues
Terminating connections
When you create a connection, you authenticate the user%