Computer Networks Architectures & Protocols

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Computer Networks Architectures & Protocols

Part One (Computer Networks Layering Models)

i.

The communication between the nodes in a data network must be correctly defined to ensure correct interpretation of the packets by the receiving intermediate and the end systems. The packets exchanged between the nodes are defined by a protocol or a communications language. There are many functions which may be needed to be performed by a protocol. These range from the specification of connectors, addresses of the communications nodes, identification of interfaces, options, flow control, reliability, error reporting, synchronization, etc. In practice there are so many different functions, that a set (also known as suite or stack) of protocols are usually defined. Each  in the suite handles one specific aspect of the communication

Advantages of layered protocol

The advantages of layered protocols is that the methods of passing information from one layer to another are specified clearly as part of the  suite, and changes within a protocol layer are prevented from affecting the other layers. This greatly simplifies the task of designing and maintaining communication systems. Also the layered protocol diminishes the complexity of networking by separating it into many functions or layers and the introduction of new features in the layer can be accomplished without changes in the other layers.
The layered protocol provides a standard to follow which means allowing inter-operability between the software and hardware vendors this is a immense advantage for the protocol.

The layered approach has proven time and time again to be the most economical way of developing and implementing any systems be they small, simple, large or complex makes no difference. This ease of development and implementation translates to greater efficiency and effectiveness which in turn translates into greater economic rationalization and cheaper products while not compromising quality.

The layered protocol reduces debugging time, this is the time that is spent debugging can be greatly reduced as a direct result of taking the layered approach to developing network protocols because debugging is made easier and faster when using the layered approach as opposed to not using it.

One of the greatest of all of the benefits of using a hierarchal or layered approach to networking and communications protocols is the greater compatibility between devices, systems and networks that this delivers.

The portability is a benefit to the layered networking protocol because it is much easier to port from one system or architecture to another, which reduces time wasting.

Disadvantages of layered protocol

The main disadvantages of a layered protocol consists primarily of overhead both in computation and in message headers caused by the abstraction barriers between the layers, this is because a message often has to be passed through 10 or more protocol layers the overhead of these boundaries are often more than the actual computation being done.

One other disadvantage is that the higher level layers can’t see what’s in the lower layers, implying that an application can’t debug where in a connection a problem is or exactly what the problem is.

Another weakness is the higher level layers can’t control all aspects of the lower layers, so they can’t modify the transfer system if beneficial for example:-

  • Controlling windowing
  • Header compression
  • CRC/parity checking
  • Specifying routing
  • Must rely on the lower protocols working
  • Can’t specify alternatives when there’s a problem

ii.

TCP/IP

The TCP/IP protocol follows the OSI model, so there is not a large way of comparing. As to TCP/IP being the most common, that is because it is a very flexible protocol that allows for routing and out of order packets.

Transmission Control Protocol/Internet Protocol (TCP/IP) is the suite of communications protocols used to connect hosts onto the internet. TCP/IP uses several protocols the two main ones being TCP and IP. TCP/IP is built into the UNIX operating system and is used by the internet, making it the standard for transmitting data over the networks, even network operating systems that have their own protocols such as Netware also support TCP/IP.

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One of TCP/IP’s problems is that it has significant problems in supporting data, which is needed for multimedia and telecom.In general, the routing is pretty unstable at times, and tends to lose a lot of packets when a switch goes down because of incoherent routing tables

OSI

The Open Systems Interconnect (OSI) is an abstract description for layered communications and computer network protocol design. It was developed as part of the open systems interconnection initiative. In its most basic form, it divides network architecture into seven layers which from top to bottom is the Application, Presentation, Session, Transport, ...

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