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This newsgroup is for communication between students for the purposes of discussing topics relevant to TDC-463.

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Free Online Networking Book Date: Sep 14, 19:21 From: John Kristoff <jtk@depaul.edu>

As if I didn't give you enough book options in our first class, there is a free online networking book which you may find helpful. I have not read through it, so I cannot vouch for the quality of the material, but a quick persual shows that it's at least worth checking out. You can access it at: http://www.seas.upenn.edu/~ross/book/Contents.htm or http://gaia.cs.umass.edu/kurose/Contents.htm John

Bits versus Bytes - Homework question Date: Sep 15, 07:10 From: John Kristoff <jtk@depaul.edu>

There is at least one homework question where you need to provide a answer using bps. In the first class, I mentioned a anomaly with how we represent bits and how we represent bytes. You often see the abbreviations Kbps (or Kb/s) as well as KB. Note that the capital 'B' typically denotes bytes, whereas the lower case 'b' denotes bits. The big difference however, is how many bits or how many bytes we are talking about. When someone says they have a 56K modem, they mean a 56Kb/s modem which equates to 56,000 bits/second. If however, someone says they have a 56KB file to transmit, the file size is not 56,000 bytes. The problem is that we count bits in powers of 10 (decimal). So 56 kilobits would be 56 * (10^3) - that's 56 times 10-raised to the 3rd power. For Mb/s (1,000,000), you'd raise 10 to the 6th power. This is pretty normal and what you might expect. If however, we were talking about kilobytes, then the quanity is measured using powers of 2. For example, 56 kilobytes would then be 56 * (2^10) - that's 56 times 2-raised to the 10 power. A kilobyte is 1024 bytes (or 2 to the 10th power), not 1000 bytes. So to drive this point home a little further... 10Kb/s = 56 * (10^3) = 56 * 10 * 10 * 10 = 56,000 bits per second 56KB = 56 * (2^10) = 56 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 = 57,344 bytes They are both close, but not exactly the same number. Also remember that a byte usually contains 8 bits. To convert from bytes to bits, multiple by 8. John

No Office Hours on 9/21 Date: Sep 15, 07:27 From: John Kristoff <jtk@depaul.edu>

Unfortunately I will not be able to keep office hours on Tuesday, September 21. If you need to schedule time to see me that week, I will be available at the same time (5:00 - 6:30 p.m.) on Wednesday, September 22. Of course, you can always contact me to setup a time which may better fit your schedule. Call or send me e-mail to schedule. John

bytes or bits Date: Sep 15, 08:22 From: Kuanjing Wang <wang_kuanjing@yahoo.com>

56KB = 56 * (2^10) = 56 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 = 57,344 bytes ( or bits?)

Bytes Re: bytes or bits (Kuanjing Wang) Date: Sep 15, 08:33 From: John Kristoff <jtk@depaul.edu>

The capital 'B' in KB denotes bytes. 56KB then is 57,344 bytes which equals 57,344 * 8 = 458,752 bits. John

Forwarding e-mail from shrike.depaul.edu Date: Sep 15, 13:32 From: John Kristoff <jtk@depaul.edu>

I noticed that a number of you prefer to use an alternative e-mail address than the one you have assigned at DePaul. If you can login to the DePaul e-mail server (shrike.depaul.edu), you can have all e-mail forwarded to your preferred, primary account. Here's how you do it. 1. Login to shrike.depaul.edu. 2. Create a file called .forward in your home directory which contains the e-mail address to forward mail to. 3. That's it. At the command prompt (assuming it's a '$'), you can create the .forward file like this: $ echo myname@preferred.e-mail.com > .forward Just type in this echo command and substitute the e-mail address above for your own personal e-mail address. Now anything sent to your shrike.depaul.edu account will automatically be forwarded on. John

DePaul e-mail Re: Forwarding e-mail from shrike.depaul.edu (John Kristoff) Date: Sep 17, 09:04 From: Patrick Duffner <pduffner@technium.com>

John do we all have DePaul e-mail by default? If so do we have to check that account for class related e-mail from you?

No DePaul e-mail account by default Re: DePaul e-mail (Patrick Duffner) Date: Sep 17, 09:20 From: John Kristoff <jtk@depaul.edu>

I'm told that we do not create e-mail accounts for all students by default anymore. I'm not sure when they stopped doing this, so if you've been here awhile, you might have one. I typically do not contact anyone directly by e-mail unless they have either e-mailed me first, asking a question, or in special circumstances (we're working on a project together). This forum should suffice for most communications. If I really need to get a hold of someone, I should be able to track them down with the help of the adminstrative office. John

Homework #1 clarification for problems 4, 8 and 10 Date: Sep 16, 09:49 From: John Kristoff <jtk@depaul.edu>

1.7, 1.27 and 2.20 refer to the chapter number and problem number at the end of the chapter respectively. So problem #7 on page 74, problem #27 on page 76 and problem #20 on page 172 are assigned. John

Homework #1 - more help Date: Sep 17, 09:13 From: John Kristoff <jtk@depaul.edu>

Someone wrote: > I'm confused with question 5. Can you give me a hint? Also, for question 7, > how do I use traceroute and find the hop? For question 5, make up some numbers for x and y, that may help. For example, say you have a 500KB file. That's 500,000 bytes which equals 500,000 * 8 = 4,000,000 bits. Say y is 10 Mb/s or 10,000,000 bits/second. How long does it take to transmit 4Mb over a 10Mb/s link? That's a simple division right? Now you just need to give you answer without using any specific numbers. Hint: don't forget about the byte to bit conversion. For question 7, you'll need a PC with the traceroute program. If you go to a command line prompt on a Windows machine, you should be able to run 'tracert'. If you run this program without any parameters, it'll display a help screen. You can run it the same way you run the PING program. Like this: tracert www.yahoo.com This will display a list of "hops" and the time associated with each response from each "hop". If you are having problems running this program and absolutely cannot figure it out, goto http://www.opus1.com/www/traceroute.html and enter www.yahoo.com into the text box, then click "Trace that puppy". The downside is that this runs the trace from the opus1.com domain and not from your PC. John

Homework #1 8 IETF working groups Date: Sep 18, 13:14 From: John Kristoff <jtk@depaul.edu>

On question #2, in case this wasn't clear, I'm looking for the 8 areas that all active working groups fall into. John

question #10 Date: Sep 19, 15:29 From: chesek

Please give some hints on how do question #10 (2.20).

Emulating phone service Re: question #10 Date: Sep 20, 08:38 From: John Kristoff <jtk@depaul.edu>

A few people have asked me about this one. I believe it's easier than most people realize. If you have 10Gb/s of bandwidth available to a neighbord over a single cable infrastructure (cable TV fiber in this case), could you somehow allow phone service over this high capacity backbone. What does it take to do phone service? At a minimum, you need to provide some ensured bandwidth (64Kb/s standard) for each phone call to the network (or the central office in telephony terms). If you just consider bandwidth is the problem, what is the answer? In that case everyone shares an equal part of the 10Gb/s bandwidth. Can you design a system that does that? Perhaps. Is it practical? Probably not. Why not? What would you practical answer be? Note that the solutions book gives one specific answer to this problem which I will explain in class. It is possible to come up with a different answer depending on your reasoning. John

Lecture notes, Homework answers, slides and computer lab Date: Sep 22, 07:35 From: John Kristoff <jtk@depaul.edu>

I have not yet had a chance to put the Lecture Notes for class #2 online nor the Homework #1 answers. They should be there sometime late tonight. I will try to put together a slide presentation for the next class as opposed to writing on the chalkboard. It's a little more work for me to do so and I'm a little pressed for time this week. I still have yet to determine the best way to get those interested in working in the computer lab to do so, but I'll probably come up with at least some basic procedures which you would be able to take and try to work through on some of the lab gear. John

Correction to Sept. 27's lecture Date: Sep 28, 09:02 From: John Kristoff <jtk@depaul.edu>

I'm glad someone was paying attention! :-) The formula I wrote on the board for determing the time to transmit after a Ethernet/802.3 collision was missing one important part. Here is the correct formula: 0 <= r < 2^k where k = MIN(n,10) Where r is the random number generated. Where n is the n-th transmission attempt. John

Core Exam Study Guide for TDC 463 Date: Sep 28, 14:02 From: John Kristoff <jtk@depaul.edu>

For those of you who are concerned about the core exam and what you'll need to know from our class, here is an outline. It looks like everything here is either covered in the assigned readings, lectures or both. Note, we've essentially covered 1 and 2 thus far (and then some!). You can post questions about these subjects in this HyperNews group or bring them to class as necessary. Topics which may appear as questions on the core exam: 1. Protocol models and layering a.) General purpose of each of the 7 ISO layers b.) General purpose of each of the 5 Internet layers c.) Difference between protocol entities (peers) and interfaces d.) How data passes up and down the stack, with appropriate headers e.) Services i.) Connection oriented vs. connectionless services ii.) Service primitives: request, indication, response, confirm 2. MAC layer interconnection a.) Transparent bridges i.) Basic operation ii.) What is backward learning iii.) Basic operation of spanning tree protocol b.) Source routing bridges i.) Basic operation ii.) What is route discovery process c.) Comparison of bridge types d.) What is a remote bridge e.) What is tunneling and how is it used 3. Network interconnection layer a.) What services are provided to transport layer i.) What is a datagram network ii.) What is a virtual circuit network iii.) Comparison of datagram and virtual circuit networks b.) Types of network services i.) What is a connectionless service ii.) What is a connection oriented service c.) Routing algorithms and protocols i.) What are the desirable routing properties ii.) Static (nonadaptive) a.) Shortest path (1) Dikjstra's Shortest Path Algorithm b.) Flooding (1)