ATM NETWORK TECHNOLOGY

ATM (Asynchronous Transfer Mode) is a high speed network technology that has become the standardized solution for the telecommunication industry, teleconferencing, videoconferencing, telemedicine, HDTV, distance learning and where high speed data transfer is required.   ATM technology integrates voice, data and video at the same time. ATM uses fixed size packets called cells of 55 bytes in length. ATM network is a high speed circuit switched network that is capable of transferring one million signals using ATM protocol. ATM is a connection oriented technology in which logical connections are established for the data communication. ATM is implemented in the WAN and telecommunication sectors. Small data cells are used for communication and ATM is designed for high speed and high traffic networks. ATM cells allow voice, data and video transfer at the same time. ATM operates on the data link layer of the OSI model and it uses UTP/STP, fiber optic or air as a communication medium.

ATM CELL BASE
It is a small unit of 55 bytes fixed length and it contains the users and signaling information in it. It has a header with very limited functionality to reduce the internal buffer and to provide the high speed transfer. ATM cell identify the cells that belongs to the same virtual channels and perform easy routing.
ATM SWITCHING
Various switching technologies have been developed in the past to provide the high speed data transfer and secure communication. ATM switching technology provides high speed data transfer due to the connection oriented technology. ATM switching technology uses the predefined routing table so guarantees the fast data communication.
ATM DEVICES
ATM basically uses two types of devices such as ATM switch and end systems. The function of the switch is to handle the transmission of the cells throughout the network. Switches accept the incoming cells from the ATM end station or another ATM switch. On the other hand, ATM end systems contain the ATM adaptors.
ATM CONNECTIONS
ATM supports two types of connections point to point and point to multi point connections. In the point to point connections, two end systems are connected bi directionally or uni directionally. The point to multi point system connects one source to the number of destinations in uni directional. The source sends the information and switch replicates it to the destinations. Unidirectional network connects two switches. A typical ATM network consists of a set of the switches interconnected by point to point links. Switch support two types of interfaces user network and network node interface. Asynchronous transfer mode technology is designed for the reliability, performance, utilization and QOS and it creates fixed channels and routes when data travels between two points. There are four types of the choice when purchasing a connection.
Constant Bit Rate: It specifies fixed size rate and data is transferred in a steady form. Variable bit rate.
Variable Bit Rate: It provides specified throughput and it is best for videoconferencing.
Available bit rate. It provides guaranteed minimum capacity but high rate is also possible when the network is free.
Unspecified bit rate. It does not provide any fixed throughput level and it is best for the file transfer where delay can occurred.
ATM ADVANTAGES
It provides fixed bandwidth and simple routing is possible due to the connection oriented technology. High bandwidth utilization can be possible so it is the best solution for the telecommunication sector, videoconferencing and QOS. There are some of the disadvantages of this technology such as high cost, cell loss due to the high congestion in the network.

What is WAN Optimization ??

How to Optimize WAN
Networks play an important role in the businesses and if the network is slow so is the business. For improving the performance there are different techniques and products are on the rise such as route control products, content delivery networks, load balancing technology, multicasting and caching.

The other techniques and methods that are involved in improving the performance of the wide area network are CIFS proxy, HTTPS proxy, media multicasting, bandwidth management, web casting and WAFS.  Deployment of the wide area network optimization appliances at the data center and the branch sites boosts the network and distributed application performance with the minimum efforts.

Improving applications performance over the networks has become the ultimate goal of the organizations.  Varying network types and applications require different solutions.  WAN accelerators and WAFS optimize the data that travel over the longer distance.  Traffic over the wire is optimized through streaming, compression, prioritization, local and centralized caching and other methods.

Optimization Techniques
The optimization software and hardware use the following techniques to boost the performance of a network.

• Staging data on the local cache
• Compressing and prioritizing data
• Streamlining chatting protocols.

Vendors
The following vendors provide the WAN optimization products and appliances.

• Cisco
• Juniper
• Blue Coat
• F5 Networks
• Silver Peak
• River Bed
• InMage
• Peribit

Most of the products provided by these vendors are the hardware based and some are the combination of hardware and software.
Juniper offers the following Networks Application Acceleration Platforms.

• WX Platforms

This platform is used to increase the application performance, application and data prioritization, WAN capacity and this platform delivers compressed output that travels at the speed 64 Kbps to 155 Mbps.

• WXC Platforms

WXC Platforms holds the on-board hard drives that are used to store the repeated data and that ultimately increase the WAN capacity by 100 folds.  WXC Platforms support the disk capacity from 40 GB to 3 TB and WAN links from 128 Kbps to 155 Mbps.

• WX CMS

WX CMS platform is used to manage multiple WX platforms and WXC platforms from one central location.  There are easy monitoring and configuration tools in this platform.  The main feature of the WX CMS is the application performance, WAN utilization, bandwidth allocation and QOS.

What is WAN ?

WAN (Wide Area Network) is a data communication network that covers a broad geographic area.  The term WAN applies to the broader telecommunication infrastructure.  Router is the main communication device in the WAN networks.

How WAN Works?
A WAN is a network of interconnected devices such as router, switches, modems, wireless devices, DSL services, frame relay devices, access servers, ISDN terminal adapters, DSU devices and WAN switches.  The most common WAN circuits are packet switching, circuit switching and point to point communication.  In WAN routing the routing table contains the IP addresses of the source and destination devices.  On the basis of the routing table, the router chooses the best possible shortest path for the packets.

A point to point link is also known as a leased line and which provides the communication between two remote locations through a carrier network such as Telecommunication Company.  In circuit switching a carrier network is involved in establishing, maintaining and terminating communication session. In packet switching, the communication devices share point to point link to transfer packets from the source and destination. Dial-up services provide cost effective solutions for WAN connectivity.

WAN Technologies
The WAN technologies operate at the lowest level of the OSI layer model.
ATM
ATM or Asynchronous Transfer Mode is a high bandwidth and high speed wide area network technology that operates at the speed of 155Mbps.  ATM is also called cell relay and it supports multiple data types such as data, voice, video etc.  ATM uses fixed sized packets for data communication that are also known as packets.

Dial UP
Dial up WAN provide the cost effective communication solutions.  Dial up demand and dial up backup is the two WAN dial up services.  In a DDR, a router dynamically initiates a call on a switched circuit when it requires sending data.
In dial backup, switched circuit is used to provide the backup services for other types of networks such as PPP or packet switching.
X.25
X.25 is a data communication protocol in the packet switched networks.  X.25 allows computers at the remote locations to communicate with each other through a centralized computer.
Frame Relay
Frame relay is a very high speed and high performance WAN protocol.  Frame relay operates at the physical and data link layers of the OSI model.  Frame relay is a networking method that is designed for the data transmission between LAN and WAN.
ISDN Lines
Integrated Services Digital Network is a WAN communication method over the regular telephone lines.
Circuit Switching
In WAN, when a router has data for the remote site the switched circuit is initiated.  When two remote networks communicate and authenticate then the communication starts.  ISDN is the best example of the circuit switching network.
Packet Switching
In packet switching the common carrier resources are shared between the remote networks.  ATM, Frame Relay and X.25 are the examples of the packet switched networks.  In this technology, the network has connections into the carrier networks and some portion of the carrier network is shared.
CSU/DSU
Channel Circuit Unit/Digital Circuit Unit is a device that is used to connect a router with the digital circuit like T1.
WAN Routing
WAN routing is a technique of forwarding the packets towards the destination based on the IP address of the next hop.

Introduction to the Computer Network Architecture

What Is a Network?
Here you will learn about computer network architecture, physical design, logical topology, protocols introduction, communication planning and basic communication technologies. To properly build, maintain and secure a network you should first know that what a compute network is and how data travels through the wired or wireless network. A person with a good networking skills will be able to tell that a network consist of a computer, cables, PRI lines, Routers, switches, NIC cards, PBXs, TIs, fiber optic and Ethernet cables.  A person who have the strong background in the data network must know that a network consists of a server, workstations, routers, hubs, WAN, LAN, fiber optic and Ethernet cables and devices. Both the telecommunication and data communication persons agree that the cabling is an essential part of any computer network.The simplest definition of the data network is to connect two more computer computers with each other to share data and resources. The network exists in different sizes and shapes, from home networks to WAN networks. Despite the different roles and various sizes of a network you can have some common similarities in all the networks such as protocols, architecture and topology/design.

  Computer Network Architectures
Basically computer network architectures are dividing into three basic types such as LAN (local area network), MAN (Metropolitan area network) and WAN (wide area network. A LAN can consist of two or more computers in the same room or building. Fiber optic or Ethernet cables are used to connect the computers in a LAN. Home networks, personal networks and office networks fall in LAN. A typical MAN consists of two or more computers at two different geographical locations in the same city.
A MAN can be wired (fiber optic cable) or wireless and a number of communication devices are used in a MAN. A WAN consists of two or more computers in two different geographical areas (different cities or countries) and there are different methods to connect the computers in a WAN such as leased lines (ISDN lines, radio waves, microwaves, dial-up connections and connectivity through satellite. The internet is a largest WAN in the world. With the invention of the wireless networking, mobile and optical technology the usage of the wires has been decreased. There are a number of the terms that describe the architecture of a network.

Computer Network Topologies
The topology or physical design is closely related to the architecture of a network. Topology defines that how the network is physically connected. There are three main types of the topologies.
• Star Topology: In the star topology the all the networking components are connected to the central point, which is a hub or a switch. The star topology is mostly in use in LAN.
• Bus Topology: In the Bush topology the networking components are connected to the same cable. This is also called linear bus or backbone.
• Ring Topology: In the ring topology the all the components are connected with each other in the form of a ring. A token continuously passes through the loop.

Network Architecture Terminology
• CAN (campus area network): CAN is a type of a network that connects the buildings/offices of a university, educational or office complex.
• Intranet: Intranet is a private network that belongs to an office, college or an organization and that is only accessible to the authorized users.
• Internet: The internet is a network of networks and connecting millions of computes with each other by different designs.
• MAN (metropolitan area network): MAN is a type of a network that is designed for a city. A MAN is larger than LAN but smaller than WAN.
• SAN (storage area network): SAN is a type of a network that is used to connect the storage related devices like RAID, file servers and tape systems.
• VLAN (virtual local area network): VLAN is a type of a network that allows computers on separate physical networks to communicate as if they were connected to the same network.
• Client-Server: Client- Server is a type of networking in which dedicated systems that provides services are called serves and the system that get these services are called work stations. The main services include file, printer, scanner, CD, Hard disk, processor, internet connection and other services.
• Peer-to-peer: This is a type of a networking where each computer shares the same functionalities. No centralized server is required in the Peer to peer networking.

Computer Network Protocols and the OSI Model
Protocol is one of the most important components of a computer network. Protocol means a set of rules, agreed upon ways or a communication language which all computer and devices understand. A protocol defines error checking, how data will be send and receive, and transmitting data between the systems. There are a large number of protocols and following is a list of the most commonly used protocol in the computer communications.
• AppleTalk: AppleTalk is a communication protocol that was developed by the Apple System to connect Macintosh computers to the printers.
• Asynchronous Transfer Mode (ATM): ATM is a type of protocol in which data travels in the form of fixed size packets. These fixed size packets provide high speed, data security, and video and voice communication over the same network.
• DECnet: DECnet is a protocol that was developed by the Digital Equipment Systems to connect the PDP and VAX systems.
• Ethernet: Ethernet is a LAN protocol that was developed by the Intel, Xerox and Digital Equipment System. Ethernet is a most widely used LAN communication standard.
• Fiber Distributed Data Interface (FDDI): FDDI is a protocol that is used to transmit the data over the fiber optic cables.
• Internet Protocols (IP): IP is a protocol transmitting data between the packet switched IP networks originally developed by the DOD (department of defense). TCP/IP (Transmission control protocol/Internet protocol) is a suite of protocol and FTP, HTTP, E-mail, Telnet are all IP protocols.
• Internetwork Packet Exchange (IPX): IPX is a networking protocol that is used by the Novell Netware operating systems.
• NetWare: Netware is a LAN protocol that is developed by the Novell Corporation.
• Signaling System 7 (SS7): SS7 is a telecommunication protocol that was developed by the International Telecommunication Union.
• Systems Network Architecture (SNA): SNA is a set of protocols that was developed by the IBM mainframe systems.
• Token Ring: Token Ring is a LAN protocol that was developed by the IBM where systems have the tokens before they transmit the data. Transmission Control Protocol/Internet Protocol (TCP/IP): TCP/IP is a suite of the protocols used to connect the computers on the internet. TCP/IP is a most commonly used protocol.
• X.25: X.25 is a protocol that was developed by CCITT for the packet switched network.
Protocols are combined with the OSI layers model. OSI model is an ISO standard for the communication system. There are seven layers in the OSI model and each layer performs the different functionalities. The seven layers are Application, Presentation, Session, Transport, Network, Data link and physical layers. Each layer know how to communication with the upper and lower layer. You can remember the name of all the layers by the following sentence.
“All people seems to need data processing”

Planning a Logical Network Design
When you plan a logical network design you can either start from scratch or upgrade an existing network. You should have the sufficient information about the networking components, hardware, protocols and topologies. You should analyze the traffic pattern, security needs, future expansion, and server capability, internet access to the clients, FTP and other things. You should also make a plan for the disaster recovery, data recovery and instant troubleshooting techniques.

What is DNS

DNS: Domain name service is an Internet service that translates domain names into IP addresses. Domain names are easy to remember because they are alphabetic. On the other end, the internet is based on the IP addresses i.e every computer on the internet is associated with a unique IP address.
The communication on the internet is carried out on the basis of IP addresses and not on the domain names. A Domain name server service translates the domain name into its corresponding IP address for example the domain name www.abc.com might be translated to 102.222.34.56. The DNS system is, in fact, forms its own network.
If one Domain name serverserve doesn’t know to translate a domain name, it looks for another one and so on until the exact IP address is returned. DNS translates between the internet names and internet addresses.

How DNS Works
DNS organizes the hostnames in the form of hierarchy. A domain is a collection of of the sites that are related because they form a network (all computers that are geographically close as well. Universities are commonly grouped in .edu domain with each university or college using a separate sub domain.
While most of the topic does not require much technical knowledge, there is one technical part of the Domain name server.
When you type a name like example.com in your internet browsers it finds a way to map that name to the internet IP numbers, by which the internet easily reach the example.com computer. For this purpose your computer uses DNS of your Internet service provider company. All internet traffic work on these numbers and the important factor is that the looking up for the name is done by Domain name server.
That computer has a list of the host names/IP address mapping, which is regularly updated by the root DNS. Root DNS servers are the master servers that can help you look up any name. All the root DNS servers copy their own data from the one master server, which is under the control of ICANN. The root servers usually have a list that where you can look for the top level domains like .com, .net, org and .info etc. The ISP sends request for the particular domain name to the root sever and root server directs the request to the master server. In this way, you get the answer with your requested domain name.
IP routing and root servers
The domain lookups go to and from the root servers because main routers on the internet, ISPs and backbones have the list that where to find it.
Domains Description
.edu This domain name is used by the educational institutes like colleges and universities
.com This domain name is used by the commercial institutes/organizations and companies.
.Org This domain is used by the non-commercial organizations.
.net Administrative hosts, gateways and other networks.
.mil This is used by the U.S. military institutions.
.Gov This is used by the government institutes.
.info Used by the Informative sites.
There is a common question that how large is the internet and how Domain name server works. Domain name server simply provides mapping between hostnames and the IP addresses. When you dial in your ISP number and access it how does it get the answer in the form of requested domain name for you. It’s most likely that ISP may not have stored the information (requested site). In this case first the ISP server will send the query to the root-servers. These are the set of very high-powered servers that know all about the top level domains like .com, .org, .net, .info and all the country domains.
So, the ISP’s name server first contact with the root-servers. If the root-servers don’t have the requested information then redirect the request to the GTLD servers for any kind of top level domain and the answers come back to the ISP’s name servers with the requested information. At each step, ISP’s name server caching all the information. The Domain name server is central to the internet because without a domain name systems (DNS) its impossible to communication on the internet.

An Introduction To The Frame Relay

Frame relay is a fastest growing network communication technology and is widely used in the corporate offices, multination companies and in the ISPs. It provides cost effective, fast and secure data communication between LAN and WAN. Frame relay is based on the X.25 technology, which was initially designed for analog data transmission. It is a fastest method of transmitting the information between two similar or different networks. Frame relay is a network communication technology that is used for the data transmission between local area network and wide area network

The data is transferred in frames and they are relayed on the data link layer. The network provides permanent and fast virtual connection PVC. Frame relay provides the service between ISDN and ATM. Over the leased telephone lines, frame relay is used to connect the LAN with the fiber optic backbones and with the WAN. The data is transmitted to the destination by means of permanent of switched virtual circuits. Many virtual circuits can exist across a transmission between because virtual circuits only consume the bandwidth when they transmit the data.

The frame relay circuits are the logical circuits that are created at the time of installation and are not created by the users at their systems. In device that is a part of the frame relay network can operate at a very high speed due to the availability of the more bandwidth. The high performance and the error handing techniques allow frame relay protocol to discard the time consuming error handling techniques. The standards of the Frame relay protocols have been developed by the ANSI and CCITT. The frame relay structure is based on the LAPD protocol.
The header of the frame has the data link connection identifier DLCI and congestion bits. When a network becomes congested i.e. it is not able to transmit any new data it begins to discard the frames and these discarded frames retransmitted so more congestion is produced. To avoid this problem several methods have been developed.
Two bits Forward Explicit Congestion Notification and Backward Explicit Congestion Notification in the header of the frame are used to signal the devices at the user end that congestion has been developed. When congestions occur the FECN is changed to 1 and in this way all the downstream nodes and the attached devices at the user end learn about the congestion in the line. The BECN is changed to 1 in the frame that traveling back to the source of the data transmission. So the source is notified of the congestion in the line and to slow down the transmission until the congestion in the line is minimized.
Frame relay works on the consumer hardware such as router and switches and each switch relays the data to the next switch in frame relay network. Frame relay also work with the meshed network because each endpoint can be connected to the different locations and so on. FR is a cost effective and standardized way of creating a wide area network. Frame relay provides error free high data transmission rate and the speed comes in a number of options such as 56 KB/s, 64 KB/s, 128 KB/s, 256 KB/s, 512 KB/s, 1.5 MB/s, and 2 MB per second.

Network Security : Brief Introduction

Network security refers to protecting computer network from the unauthorized access, hacker’s attacks, viruses, spyware and internal and external threats.  It also refers to protecting the network from the unauthorized modifications, data lost, destruction, physical attacks and the protection of the company’s assets. Computer networks are being used to conduct the transactions, communications, data and resources sharing, orders processing, voice communication among the businesses and the individuals.   

Every computer network without proper security mechanisms can be attacked by the hackers, viruses and intruders so it is the most important responsibility of the computer network administrators to implement the security solutions.

A personal computer, gateway computer and the laptops are the common point of attacks.  Unauthorized users can steal the company’s important data.  Being an administrator you need to know the common threats and implement the solution to deal with them.  The common network threats include the following.

Common Threats

• Viruses
• Hacking attacks
• Spyware
• Adware
• Malware
• Trojans
• Web Worms
• Rootkits
• Honeypots
• Identity lost
• Sniffers
• Physical Threats
• Dangerous Macros
• Eavsdropping
• Security Vulnerabilities
• Risks from the Naive employees.
• Denial of service attacks.
• Data Interception.

Just ask yourself that are you ready to deal with any of the above mentioned threats?  If your answer is NO then your network is at great security risk.  As the uptime and the security are the most important thing in the computer network so you need to implement the solutions to deal with these threats. A computer network can be kept secured by implementing the following techniques and using the tools.

• Install an up-to-dated antivirus program on all the computers and regularly scan them.
• Install an up-to-dated anti spyware program.
• Configure a software or hardware firewall on the gateway computer.
• Limit the rights of the users in your network.
• Use monitoring, diagnosing, troubleshooting and network management tools.
• Implement an intrusion detection system as it will determine that if your network is under attack or not.
• Use strong password, digital authentication keys, and security certifications to identify the users and control their activities.
• Monitory the online activities of the users through he monitoring software and block the suspicious and potentially risky online applications and the websites.
• Encrypt your messages and data while transmitting over the network.  Encryption ensures that your data cannot be intercepted or read by the unauthorized users.
• Apply security patches against the known vulnerabilities.
• Update your operating system regularly.
• Lock your server room and no unauthorized user should be allowed to enter in the server room.
• Keep inventory of all the devices including computers, hubs, switches, routers, cables, printers and scanners etc.
• Block the unwanted ports and services.
• Increase the security of your web browsers.
• Regularly take backup of your critical data.