Monday, January 24, 2011

CS610 Assignment 5 Solution

CS 610 Computer Networks
Assignment # 05
Fall 2010
Total Marks = 20

Your assignment must be uploaded / submitted before or on January 31, 2011.

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The assignment has been designed to enable you develop the understanding about the transport protocols and network address translation.

Note: Material that is an exact copy from handouts or internet would be graded
zero marks. Your solution should consist of the material found through different sources and written in your own words.

Assignment Statements:

Q1. Differentiate between internet protocol and transport protocol with the help of examples.
                                                                                                    (10 Marks)

Q2. Describe the pros and cons of NAT?
                                                                                                    (10 Marks)



Q1. Differentiate between internet protocol and transport protocol with the help of examples. (10 Marks)

Helping Material:-

Internet Protocol
The Internet Protocol (IP) is the principal communications protocol used for relaying datagrams (packets) across an internetwork using the Internet Protocol Suite. Responsible for routing packets across network boundaries, it is the primary protocol that establishes the Internet.

IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering datagrams from the source host to the destination host solely based on their addresses. For this purpose, IP defines addressing methods and structures for datagram encapsulation.

Historically, IP was the connectionless datagram service in the original Transmission Control Program introduced by Vint Cerf and Bob Kahn in 1974, the other being the connection-oriented Transmission Control Protocol (TCP). The Internet Protocol Suite is therefore often referred to as TCP/IP.

The first major version of IP, now referred to as Internet Protocol Version 4 (IPv4) is the dominant protocol of the Internet, although the successor, Internet Protocol Version 6 (IPv6) is in active, growing deployment worldwide.

Q2. Describe the pros and cons of NAT?

 Network Address Translation or NAT is a technique that allows the translation of local network addresses or the internal IP addresses (used within an organization) into globally unique IP addresses that help identify an online resource in a unique manner over the Internet. The process is also referred to as Network Masquerading or the Native Address Translation. Network Address Translation allows multiple resources within an organization or connected to a local LAN to use a single IP address to access the Internet. The idea of Network Address Translation is very simple indeed. It essentially abstracts internal addressing from the global IP addressing used over the Internet. This abstraction allows helps the network resources to get over a shortage of the address space by mapping relatively few real IP addresses to the abundant local IP addresses created locally by the Proxy server for addressing purposes. It allows the use of different addresses over the local and global level and local sharing of IP addresses over the Internet.
An increasing usage of the Network Address Translation was a direct result of the limited address space offered by the erstwhile Internet protocols such as the IPv4 that carried the bulk of the Internet traffic. NAT became a popular mechanism to overcome the shortage of unique IP addresses for individual network resources over the Internet. The Network Address Translation protocol maps the internal addresses to the real IP addresses that are required for communication process over the Internet.

                         Types of NAT:

1.Full Cone NAT The term Full Cone NAT is also commonly referred known as one-to-one NAT. Full Cone NAT allows the mapping of various external (non local) address ports to the corresponding internal addresses ports in a symmetrical manner. 

2.Restricted Cone NAT This allows the local IP address and port number to be mapped to a particular external IP address and port number respectively. The relative mapping in the internand external domains is not disturbed in the Restricted Cone network address translation. 

3.Port restricted cone NAT As the name suggests, the Port restricted cone NAT restricts the portnumbers that are used for communication purposes over the Internet. All the external communication is directed to particular communication port except if there is a continuous communication with an application over a specific communications port. 

4.Symmetric NAT The communication process directed outwards is mapped to a unique externaladdress along with a port number. This scheme imparts a logical symmetry to the process of external network access by the resources connected to the LAN.

In actual practice a pure NAT implementation is rarely used. Rather, a combination of the above
types is implemented to achieve the desired network configuration



Q1. Differentiate between internet protocol and transport protocol with the help of examples.


TCP is also called or known as Transmission Control Protocol. It is main protocol of the Internet Protocol collection. Internet Protocol is also called IP. The Internet Protocol (IP) is the primary communications protocol used for transmit datagram which is packets. Accountable for steering packets across network limitations. The two major concern of TCP are the two end systems. First are web browser and second one is web server.
For example,
TCP give the release of a stream of bytes from a program from one computer to another computer. TCP is also responsible of controlling size, flow control, the rate of data exchange, and network traffic blocking.
The first major version of IP is as Internet Protocol Version 4 (IPv4). It is the leading protocol of the Internet and in the other side Internet Protocol Version 6 (IPv6) is in rising operations globally.

TCP offer communication services at a middle level among an application program and the IP. Its indicate that when an application program wants to send a large piece of data across the internet using the Internet Protocol in its place of breaking the data into sizes that will fit the IP and using a sequence of requests from the IP. The software is able to issuing a single request to TCP and allows to protocol handle the information of the IP transfer. TCP sense problems that occur in the IP Requests retransmission of the packets that were lost reorganize the order of the packets. Now they are put reverse into their appropriate order and help to reduce network.

·     TCP is main operating on a comparatively high level and IP work at a lower level.

·     TCP gives communication services at an intermediate level between an application program and the IP. IP encapsulates all data and is connectionless.

·     TCP is the protocol that major Internet applications rely on applications such as the WWW, email, and file transfer.

Q2. Describe the pros and cons of NAT?


NAT or Network Address Translation is a method that permits the conversion of local network addresses or the private IP addresses used within an LAN into worldwide matchless IP addresses that help recognize an online resource in a unique manner on Internet. An upward usage of the NAT was limited address space offered by the previous Internet protocols such as the IPv4. NAT turn into a popular system to overcome the lack of unique IP addresses. The NAT protocols plot the private addresses to the valid IP addresses that are necessary for communication process over the Internet.

NAT Pros and Cons:
Network Address Translation does not allow a true end-to-end connectivity that is necessary by some real time applications. An amount of real-time applications require the formation of a logical tunnel to swap the data packets rapidly in real-time. It needs a fast and faultless connectivity of any mediators just like proxy server that inclined to make difficult and slow down the connections process.
NAT creates difficulties in the performance of Tunnelling protocols. Any communication that is routed through a Proxy server be likely to reasonably slow and prone to trouble. Positive significant applications offer no space for such shortfall.
Examples telemedicine, teleconferencing. Like this applications find the process of network address translation as a block in the communication network creating preventable twist in the end-to-end connectivity.
NAT do something like out of work channel in the online communication over the Internet. The two causes for the extensive fame and following acceptance of the network address translation process were a lack of IPv4 address space and the safety fear. These concerns have been fully satisfied in the IPv6 protocol. In the IPv6 gradually substitute the IPv4 protocol. The NAT process will turn into out of work and worthless even as consuming the limited network resources for providing services that will be no longer required over the IPv6 networks


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