The Advanced Research Project Agency Networ

Published Date: 02 Nov 2017

As the Advanced Research Project Agency Network(ARPANET)scientists and network engineers are striving almost from early 1980's just for the sake of the most efficient and which is very quick in accessing the information transfer, now they have invented Asynchronous Transfer Mode which has all the reliable features of the present generation needs. It is a technology where switching, multiplexing sort of technologies uses fixed length like 53byte,45byte which includes in the header called as cells. Since it is a connection based technology if a connection is to be started then both the end points are met to accomplish a connection. It has a wide range of usage capabilities such as complicated technology, features which can handle any cast of data such as voice, text, video, image.

ADOPTED FEATURES:

It is a switching technique which has been adopted to configure the combination of both circuit and packet switching technologies. It is an asynchronous mechanism which defers from synchronous transfer mode, it can make time slots when they are demanded. One of the attracting feature is less latency transfer in the present multimedia usage such as video, audio and voice over interconnecting LAN's which is been trending big companies. A very low delay in the data transfer over a network which makes the transmission very fast.

ATM ARCHITECTURE:

ATM possesses a layered type of method. They are

1) PHYSICAL LAYER: the network elements connections are held and changes it to the electrical or optical format.

2) ATM LAYER: fixed sizes of the partial transfer of 48 octet data units and payload may consume or remove 5 byte.

3) ATM ADAPTATION LAYER: It basically have two sub layers called as Convergence sub-sub-layer which works at the sending and receiving nodes to reassembles the nodes.

There are different AAL services called as AA1,AA2, AA3, AA4, AA5 in which the first two support the video, voice and continuous traffic and the rest of it fetches the data communications. And these are again determined to support four service classes A,B,C,D which gives information of whether source and destination require the timed slots or not. Or even the bit rate of data, let say variable or constant and the mode of the connection flow.

Now let us consider the classes

Class A: It requires a timed relationship between source and destination and may use the telephone network. It is synchronous and connection oriented with a constant bit rates.

Class B: It is almost the same thing as Class A but here it the bit rate will be variable, so it can be used in a video compression technique for example a packet video.

Class C: It is an asynchronous technique in a connection oriented and changes the values, for example we can consider frame relay.

Class D: Connectionless environment for example SMDS.

The services mentioned above are maintained by AAL and it depends from each layer.

AAL1: It sets the time information of source and destination and also controls the flow of data whether it is lost or not.

AAL2: It does the same as AAL1 do and moreover it also uses the variable bit rate services. With the help of the sequence number the lost data frame can be caught.

AAL3/4: It is again break in to two sub-layers, they are Convergence Sub-layer and reassembly sub-layer. It is the image of the above mentioned process but a very slight change which carry variable data and without any timing relationships.

AAL5: Given a length field for the error detection and also a 32bit CRC which is used per frame. Also used in LAN emulation which becomes a choice in adaptation layer. It satisfies all the requirements of class C structure.

http://www.cellsoft.de/telecom/pics/atmprotocol.gif

fig::1) reference number

ATM LAYER:

It sets the parameters and provides services in the top layers for example multiplexing several atm on a dedicated path. And it also ATM cells in their respective ATM cell headers, keeping in mind of prioritization and control in managing the traffic. It hits the ATM cells into the physical layer for their furthur transportation.

Bb726929.async01(en-us,TechNet.10).giffig: ref num 4

ATM Cell header Fields:

Generic path identifier (GPI) : It is a 4-bit GPI field which includes data control at UNI level.

 

 Virtual Path Identifier (VPI)—The VPI is an 8-bit field in a UNI cell &whereas in NNi cell it is a 12-bit field. .

  

Virtual Channel Identifier (VCI)—Its a 16bit field.

 

Payload Type (PT)— It tells whether it contains user data and control data. It is o for the first bit if sets up to data and bit 1 for the control data. The next bit indicates congestion(0=no congestion,1=congestion) and the third bit tells last bitus single AAL5 frame(1=Last cell for frame)

Cell Loss Priority (CLP)— It defines if the cell should be discarded if it encounters congestion as it moves through the network.

   

Header Error Control (HEC)— First four bytes of the header's checksum is looked up.

Some sort parameters are maintained to find out the Quality of service and Traffic management.

Quality of service: In an ATM connection there are several aspects mainly accuracy, reliability which all are depending upon the parameters based on performance. Negotiable and Non negotiable parameters are set to maintain the quality of service.

Traffic parameters: It defines how well the traffic is characterized over ATM network.

PHYSICAL LAYER:

The displacement of cells can be handled by physical layer in the transport medium and there are several standards to be attributed but are evoluted later on. SONET and SDN are the two mediums which are very frequently used by the ATM and are transmitted at a range of 1.544mbps to 622mbps.

Establishing Connection: Like as x.25 and frame relay ATM also uses two types of methods:

PVC: Permanent Virtual Circuit-The two end points connection establishment is provided by the network provider and their values(VP1,VC1) will be entries of the given table.

SVC: Switched Virtual Circuit- to establish a connection at any point of time a new virtual circuit is needed.

ATM APPLICATIONS: As the world is updating day by day it requires more compatibility and efficiency of providing practical applications in to the real world. Some of the Key applications used are Video conferencing, Desktop conferencing, Mobile computing, satellite communications and many other multimedia services.

CONCLUSION:

In this emerging world a promising technology called ATM has launched with lots of new applications supported for multimedia and various other services. With a very low delay in the transforming data and ability of moving image, video, voice and other materials in a medium at high speeds. Domain boundaries can be crossed over a network and interdomain communication policies are implemented when required.

FIBRE CHANNEL

INTRODUCTION:

Fibre channel is a set up which brings a trademark in the upcoming world which supports heavy data to be sent from various devices such as computers, disk arrays, servers with high reliability protocols and moreover at spectacular speeds. Being so demanded in today's world it has been greeted by several workstations such has business agencies, high profiled institutions and many administrations.

STANDARDS:

As per the ANSI standard and derivations the Fibre channel is said to be a transport protocol which handles over its cabling up to a distance of 10km. It can be elaborated in both ways, "Single mode- it allows only a single pathway, or mode, or light to travel within the fiber. Multi mode- allows multiple modes of light, it is best small distance applications"[5]. allows for a speed of 1gb/sec, 2gb/sec, 4 gb/sec.

figure: FIBRE CHANNEL ADAPTER CABLE ref: [5]

TOPOLOGIES:

Fibre channel contains of three distinct topologies which are standardized and satisfies various different applications with several requirements prescribed in it.

POINT -TO -POINT: It is the basic and simple addressing topology to configure and can be connected directly in between two end points over a network.

fig-ref[5]

ARBITRATED LOOP: It involves multiple end points because it uses ring topology in it and individual transmission path. To get interconnected within a loop then a hub interconnects each end points. This arbitrated process make sure to tell which end point is handling the loop and the maximum devices that can connect is 126.

fig-ref[5]

SWITCHED FABRIC: Switches are the most effective once in this topology because it takes care of high speed interconnection devices which can be more than one at a time and also it sets flexibility for the best use at the end points. Sometimes we require multiple switches are needed to create a single fabric. Within a single fabric, frames can are set to their destiny points and simultaneously interconnections of multiple ends happens.

fig-ref[5]

LAYERS: It is described in five different layers

1)FC1: It is lowest level and it gives the physical set up of the system, optical, including fibre.

2)FC1: Sets the encoding and decoding, special characters and flow control at data link layer.

3)FC2: It states the head protocols and consists of fibre channel core at Network layer.

4)FC3:It indiactes cummon facilities which requires latest featurres like stripping, hunt groups, multicast[6].

5)FC4: It maps the protocol and it is the top layer in the sturcture and applications are executed at this channel.

TERMINOLOGY:

It is been assigned some terms in which it can be represented

Node: End point containing some information for example computer, peripheral devices.

Port: Each node is fixed to a port to connect a topology which is called as N-port.

E-port: to build a switched fabric and it is called a expansion port

F-port: Fabric port connects N-port to a switch if a loop cable does not exist.

G-port: this is Generic port

L- port: it is a loop port.

fig: ref [5].

ADVANTAGES:

1) It gives extremely high distance for the cable to extend of almost 30m to 10km.

2) The devices can be easily accessible over a shared multiple servers and the devices can be around 16million at the most.

3) It is a successful storage network with its high integrated interoperability.

4) Surprisingly over 500 companies are major enterprises get bonded with the fibre channel just because of its accurate delivery of the customer.

5) It's low expensive and more reliable.

CONCLUSION:

As of now fibre optic is ruling the world with lots of ingredients in it which is giving the best usage. When compared to ethernet and ATM it is much better with respect to reliablity and speed. Full duplex and speed of 100m/b tranmission which is the best. Many scientists say that the fibre channel is the cheapest commodity to what it provides.

REFERENCCE 1) http://www.slideshare.net/seanraz/10-slides-to-atm

2) https://www.iol.unh.edu/services/testing/atm/training/ATM_Tutorial.pdf

3) http://www.123helpme.com/view.asp?id=54179

4) http://technet.microsoft.com/en-us/library/bb726929.aspx

5) hugo cacote@ CERN IT

6) http://hsi.web.cern.ch/HSI/fcs/spec/overview.htm