$3.$Internet Applications.

a$)$In peer$-$to$-$peer applications where all nodes act as both providers and consumers,$$explain why the terminology of 'client' and 'server' persists. $(6$ marks$)$

b$)$Describe how web caching can reduce the delay in receiving a requested object. Will Web caching reduce the delay for all objects requested by a user or for only some of the objects? Discuss. $(8$ marks$)$

c$)$Explain clearly the issues related to non$-$persistent HTTP application protocol and explain how persistent HTTP application protocol overcomes the issues effectively. $(8$ marks$)$

Suppose Ironman has a web$-$based email account $($such as Hotmail or Gmail$),$ and sends a message to Spiderman, who accesses his mail from his e$-$mail server using IMAP. Discuss how the message gets from Ironman$$s host to Spiderman$$s host with the help of a diagram. Be sure to list the series of application layer protocols that are used to move the message between the two hosts.