Date: Wed, 16 Jan 2008 21:26:24 -0600 (CST) From: Mark Jacobson To: 810-023-01-spring@uni.edu Subject: Re: [810-023-01-SPRING] Readings and WRT 112 lab on Friday... Hi 023 students, I have updated the web page: http://www.cns.uni.edu/~jacobson/c023.html It has suggested reading and assignment to do, ideally as a PRELAB to spend some time on BEFORE Friday's Wright 112 lab class. It also has review of what has been covered so far in class and preview of what we will do the next few weeks. Please DO NOT THROW review Transport THROW Port numbers - #80 for web servers Network NOT IP number w.x.y.z 134.161.y.z for uni.edu (32 bits) Data Link DO NIC/NAC/MAC addresses (48 bits) Physical Please In today's class, the client was my laptop PC, the server was www.uni.edu web server. Both the client and the server have a PROTOCOL STACK that enables the network communication. The www.uni.edu web server uses PORT #80, which is the standard port number for web servers. The IP number of that www.uni.edu web server can be found by doing: ping www.uni.edu or tracert www.uni.edu (or if UNIX or Linux use traceroute www.uni.edu). The IP number and the NIC (Network Interface Card) address of my laptop was found using ipconfig (ifconfig on Unix/Linux) and by using ipconfig /all to get the NIC (NAC) address. There is no way to find out the NIC address of www.uni.edu server, even if I could sniff the network and capture packets. Here is an example from a past semester that was using PORT #23, which means it was using telnet to login to sunny.uni.edu or some other machine. (Do NOT use telnet these days. ssh encrypts your connection and protects your privacy and password. telnet does NOT encrypt your packets. More about this later). ------ ssh uses port number 22 instead of port number 23. different services -- use different port numbers. Protocol Stack Protocol Stack of client of server --------------- ---------------- 3905 23 Port numbers Transport Transport 192.168.0.100 128.153.4.131 IP numbers Network Network 00:07:E9:53:87:D9 ??:??:??:??:??:?? NIC or MAC address Data Link Data Link --- - -- ssh (Secure SHell) --- - -- secure, because fully encrypted remote login (ssh) and copy (scp and sftp) service, please use exclusively this full substitute instead of the obsolete ftp, telnet, rlogin, rsh, rcp and so on! -------- ------ Question for the day: Read about http protocol and verify that it uses port 80. What port number does https use? http://www.lb.shuttle.de/apastron/ports.htm has the answers and explains briefly the difference between http and https, as well as what port numbers they each use. Today, the phrase could have been - - - - - - - PLEASE DO NOT THROW SNOWBALLS PAST AUTOMOBILES - - - - - - - January 16th, 2008 can look like this: 01/16/2008 (in decimal, base 10) or it can look like this: 1/10000/11111011000 (in binary base 2) or like this: 1/10/7D8 (in hexadecimal, base 16) Perhaps 01/16/08 mm/dd/yy format is easier to figure out in binary, as 01/10000/1000 1 16 8 Mark On Wed, 16 Jan 2008, Mark Jacobson wrote: > Please read over Exercise 1.1 Examining a Quiet Network with Ethereal > and Exercise 1.2 Protocol Layering. > > Pages 1 through 29 for these two "chapter" of our textbook. > Today you saw the Protocol Pane and the Raw Pane in action during > class. Know those two terms before Friday (page 11 of book). > > The List Pane should also be known. Which Pane is used to determine > what packet we see in the other two Panes? > > List or Protocol or Raw? > > Protocol Layering is explained in 1.2 and page 17 shows a very nice > diagram of the 7 layer model and compares it to the TCP/IP 4 layer > model (also called a Stack or the Internet Protocol Stack model). > > What are the two most common TRANSPORT layer protocols? > > Which of these two is the more reliable? > > What are the two main things that are in an Ethernet Header? > > Please Do Not Throw Sausage Pizza Away > > Which OSI layer is the Ethernet Header associated with? Name it. > You will see Src: and Dst: > > Which OSI layer are port numbers associated with? You will see > Src Port: and Dst Port: as you read and look at the diagrams > and Ethereal snapshots in chapter 1.2 Protocol Layering. > > Which OSI layer are IP numbers associated with? > You will see Src Addr: and Dst Addr: in the appropriate Pane > as you look at the Ethereal screen snapshots in the book. > > The class web page is at: > > http://cns2.uni.edu/~jacobson/c023.html > > Please look over the IP Packet Format diagram at > > http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ip.htm#wp4148 > > Please look over the TCP Packet Format diagram at > > http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ip.htm#wp3664 > > Please look over the UDP Packet Format diagram at > > http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ip.htm#wp1375 > > Which of the 3 is the simplest diagram? > > ---------- > We will look at these in WRIGHT 112 lab class on Friday. > ---------- > > The class web page is at: > > http://cns2.uni.edu/~jacobson/c023.html > > Mark