December 1999
AN215 : ADVANCED NETWORKING

QUESTION 2

Total Marks: 15 Marks

• Question 1
• Question 3
• Question 4
• Question 5
• Cover Page

SUGGESTED SOLUTIONS
Solutions and allocated marks are indicated in green.
Return to Question 2

What are the benefits of using layered architectures in networking?
Award marks for anythree of the following,or other valid points.
Better interconnection for hardware and software from different vendors (1 mark).
Good design principle;separation of concerns (1 mark).
Better scope for standardization (1 mark).
Modular construction (1 mark).
Facilitates the definition of open systems (1 mark).

The TCP/IP protocol suite is based around a four-layer model.Name each layer,and provide a suitable example of a protocol or network used in each layer.
Application layer —SMTP,FTP,or HTTP (1 mark).
Transport layer —TCP or UDP (1 mark).
Network layer —IP (1 mark).
Interface Layer —ethernet (1 mark).
Allow credit for other relevant examples.If examples are missing,award no more than two marks.

OSI and TCP/IP both describe layered protocols for host-to-host communication. Could TCP/IP be said to be an implementation of the OSI reference model?Explain your answer.
No (1 mark).TCP/IP is another reference model,not a single implementation (1 mark).TCP/IP has fewer layers than OSI (1 mark).TCP/IP is widely deployed whilst OSI still remains largely on paper (1 mark).
Award marks for these or other relevant points.

 Which layer of the OSI reference model deals with internal data representation issues of communicating systems?If this layer were absent (as it is in TCP/IP)which layer would perform this function?What would happen if no layer performed this function?
This is the presentation layer (1 mark).In its absence,the application layer must keep track of the different formats (1 mark),and convert where necessary (1 mark).If no layer did this,data transfers would fail;text would become gibberish;etc.(1 mark).
Award marks for these or other relevant points.