7. How do local area networks (LANs) differ from metropolitan area network (MAN)?
A local area network (LAN) is a group of microcomputers located in the same general area. It covers a clearly defined small area, such as an office, home network ,one floor or work area, a single building, or a group of buildings. While a metropolitan area network (MAN) connects LANs and BNs located in different areas to each other and to WANs. MANs typically span between three and 30 miles. For example a large university may have a network so large that it may be classified as a MAN. The MAN network usually exist to provide connectivity to local ISPs, cable tv, or large corporations but will not extend beyond the boundaries of a town, city, or metropolitan area.Thus, a MAN lets two remote nodes communicate as if they were part of the same local area network. A MAN usually consists of a number of interconnected LANs and WANs. [Dennis, A. & Fitzgerald, J. (2009), p.31. Business data communication and networking. Wiley]
Also LAN are usually connected by Ethernet cables,have high speed connections and relatively inexpensive while MAN are often interconnected wirelessly using microwave radio links or fiber-optics and provide moderately fast transmission rates but can prove costly to install (very expensive).

14. Explain how a message is transmitted from one computer to another using layers?
In a network of computers each computer connected must have a unique IP address.

IP: 1.2.3.4 IP: 5.6.7.8
When a message is sent from one computer to another, it travels down the protocol layers of the model, and then up the layers of the stack on the other computer. The application layer is the application software used by the network user. The Transport Layer guarantees that the receiver gets the data exactly as it was sent. It is responsible for delivering messages from a specific process on one computer to the corresponding process on the destination computer, it can also detect lost messages and request that they be resent. The network layer takes the message generated by the application layer and if necessary, breaks it into several smaller messages. It then addresses the message(s) and determines their route through the network, and records message accounting information before passing it to the data link layer. “The Data Link Layer is responsible for delivering the data without errors to the next layer. It formats the packets for transmitting after delivery, defines the network-frames. This layer synchronises the transmission and is responsible for error-control on frame-level, also error-correction so that information can be transmitted from the physical layer”. The physical layer is the physical connection between the sender and receiver, including the two computers and physical media (e.g., cable). [http://www.citap.com/documents/tcp-ip/tcpip006.htm]

17. Describe two important data communications standards-making bodies. How do they differ?
ITU International Telecommunication Union coordinates standards for telecommunications with its base in Geneva, Switzerland. The ITU-T (Telecommunications group) ensure the efficient and timely production of standards covering all fields of telecommunications on a worldwide basis, as well as defining tariff and accounting principles for international telecommunication services. The Internet Engineering Task Force (IETF) is a non-profit organization founded to provide leadership in Internet-related standards, education, and policy. It is dedicated to ensuring the open development, evolution and use of the Internet for the benefit of people throughout the world [http://en.wikipedia.org/wiki/ITU-T]
ITU standards cost money, and are copyrighted with statements that make putting them on the photocopier to underscore a debate point a debatable practice while IETF, on the other hand, has always declared that the RFCs defining their standards must be freely available over the Net, and that anyone can copy, reprint, include, quote from or generally use the documents at any time. This makes starting, for instance, an implementation project for an IETF standard as a hobby project a very cheap proposition, while a similar effort on an ITU document would take a significant up-front investment if the documents were not already available in the organization.
REFERENCES
[Dennis, A. & Fitzgerald, J. (2009). Business data communication and networking. Wiley]
[http://en.wikipedia.org/wiki/ITU-T]
[http://www.citap.com/documents/tcp-ip/tcpip006.htm]