[heroine]

dear all,

can you please explain these questions below in networking...

your help is really appreciated...

best regards,




DHCP
To configure a new computer to be attached to the Internet without using autocon- figuration services such as DHCP, you need to specify four parameters in order to make the Internet- working part work properly. Name these parameters, and for each parameter describe why it is important.

DNS
Assuming that an attack would succeed in bringing down all of the root servers in the DNS system, what implications would that have to the operation and usability of the Internet?



Multiple Access

1)
a) Protocols like ALOHA and CSMA/CD are also called statistical multiplexing protocols.

Why? What are the advantages as compared to TDMA, FDMA, and CDMA?

b) Suppose nodes A and B are on the same 10Mbit/s Ethernet segment (CDMA/CD).

Node A begins transmitting a frame and, before it finishes and before the frame reaches B, also node B begins transmitting a frame. What is the condition that both A and B

can detect the collision? Assuming that the propagation delay between the two nodes is 225 bit times (1 bit time = 1 bit / 10Mbit/s), what is the minimum frame size allowing collision detection?


2)

In this problem you will derive the efficiency of a CSMA/CD-like multiple access protocol. In this protocol, time is slotted and all adapters are synchronised to the slots. Unlike slotted ALOHA, however, the length of a slot (in time) is much less than a frame time (the time to transmit a frame). Let T be the length of a slot. Suppose all frames are of constant length L = kRT, where R is the transmission rate of the channel and k is an integer. Suppose there are N nodes,each with an infinite number of frames to send. We also assume that P (propagation time) is smaller than T, so that all nodes can detect a collision before the end of a slot time. The protocol is as follows:

• If, for a given slot, no node has possession of the channel, all nodes contend for the channel; in particular, each node tranmits in the slot with probability p. If exactly one node transmits in the slot, that node takes possession of the channel for the subsequent k − 1 slots and transmits its entire frame.

• If some node has possession of the channel, all other nodes refrain from transmitting until the node that possesses the channel has finished transmitting its frame. Once this node has transmitted its frame, all nodes contend for the channel.

Note that the channel alternates between two states: the productive state, which lasts exactly k slots, and the nonproductive state, which lasts for a random number of slots. Clearly, the channel efficiency is the ratio of k/(k+x), where x is the expected number of consecutive unproductive slots.


(a) For fixed N and p, determine the efficiency of this protocol.

(b) For fixed N, determine the p that maximises the efficiency.

(c) Using the p (which is a function of N) found in (b), determine the efficiency as N approaches infinity.

(d) Show that this efficiency appraoches 1 as the frame length becomes large.

[LTheobald]

Sorry Heroine but this looks like your homework and that means we can't/won't do it for you.

These questions should be easy to answer after a bit of internet research. Try typing some of the keywords in the questions (e.g. "DHCP" & "parameters") into a search engine. Also try Wikipedia.

[ScottGem]

Another good glossary of computer terms is whatis.com. But I agree with LT, we are not here to do your homework for you. If you want to do you own research and ask us to critique your answers that's one thing. But you instructor gave the assignment to YOU so you can learn by finding the answers.

[Chery]

Boy am I glad that I am not the only one with this opinion! I also belong to the Wondir forum, and most of the questions there are related to reports or papers that young people have to do for a 'school' project. They actually expect us to search the net and/or give them the answers to print out and hand in. I always explain that there is still such a thing as a library and now the network. When I was going to school, there were no calculators, computers, etc. I had to do my homework the hard way and I think I learned a lot more through this effort. You can't believe some of the responses or ratings I get from these (to use a harsh phrase) freeloaders. Thanks for not letting me feel alone in this. I do, however, go into the net and look up the subjects for myself later and enjoy the 'refresher' courses it provides me... :cool:

[ScottGem]

Hi Cheryl.
I've been doing this (helping out on Q&A sites) for a long time (close to 20 years now). In most of the sites I've participated in, this viewpoint has been held by the vast majority of regulars. Its one thing, to critique the work someone does, or give them some direction about where to find the answers. But when someone just posts their assignment and asks us to do it for them, ummm no!

Scott<>

[Chery]

Absolutely! And that's the way it should be. I make no exceptions, I find sites to help out and direct them toward their goals, but that's it. Otherwise, I could to it as a home-job making money. But that's not the point of forums or helping others, which I like doing more - helping when I can with the knowledge I've experienced in my life. Thanks again for letting me know I was right.

[fredg]

Hi,
You can do research at any search site, of which some are listed below. Just simply type in your word, then go to any of the many links it will find.
http://www.google.com
http://www.dogpile.com
http://www.mama.com
http://yahoohoogle.com

There are others.
Best of luck,
fredg
PS; You will find that at most question/answer sites, it is difficult to find anyone who will answer all questions, especially if they seem like any type of research or homework questions.