From jacobson@math-cs.cns.uni.edu Tue Jan 13 14:36:10 2004 Date: Tue, 13 Jan 2004 14:33:56 -0600 (CST) From: Mark Jacobson To: 810-023-01@uni.edu Subject: [810-023-01] Page 522-523 Network Classes A, B and C Hi 023 students, Look at the textbook pages 522-523 and see the dotted decimal notation as well as the concept of network classes (A or B or C) explained. Pages 520 and 521 also review a few of the concepts about IP addresses and octets that we talked about today. An IP address is four 8-bit octets, or 32 bits. It is written in dotted decimal notation, w.x.y.z where each of the decimal numbers will be in the range of 0 00000000 to 255 11111111 because 8 bits (one byte) expresses that range of numerical values in base 10 decimal. Zero through 255. ALL UNI IP addresses start with 134.161, so the IP address form w.x.y.z for any UNI address will be 134.161.y.z ***** Tracing route to panther.uni.edu [134.161.1.13] www.uni.edu is panther.uni.edu is 134.161.1.13 Four octets 134 and 161 and 1 and 13 each representing EIGHT bits (one byte) --- --- - -- w = 134 = 10000110 x = 161 = 10100001 IP address = 32 bits = 32 binary digits y = 1 = 00000001 z = 13 = 00001101 Class A 0xxxxxxx Where x is either 0 o 1 Class B 10xxxxxx Class C 110xxxxx UNI is a class B network, since 134 begins with 10 in binary. math-cs:~/web> bc <----- bc basic calculator - - obase=2 <----- set output to base 2, obase=2, to binary. 134 <----- input is still decimal, base ten. 10000110 <----- output of 134 in binary is 10000110 10000110 10xxxxxx Since it begins with 10 binary digits, and also since 134 (value of UNI IP address first octet) is in the range 128 thru 191, we know UNI is a class B TCP/IP network. See page 523 of the textbook, Table 11-1, for a nice diagram of this. Microsoft(R) Windows NT(TM) (C) Copyright 1985-1996 Microsoft Corp. C:\>tracert www.uni.edu <---- tracert instead of traceroute for Windows NT Tracing route to panther.uni.edu [134.161.1.13] over a maximum of 30 hops: 1 <10 ms <10 ms <10 ms starbase1.uninet.uni.edu [134.161.128.1] 2 <10 ms <10 ms <10 ms panther.uni.edu [134.161.1.13] Trace complete. C:\> bebop:~/web> bc <------- bc calculator again, on cowboy.cns.uni.edu which is either bebop, julia, spike, obase=2 jet or ????? 161 10100001 134 10000110 See you on Thursday in CEEE room 20. Don't worry about understanding this now. You will be comfortable with all of the above by March or April! :-) Mark