Lecture13 - Tuesday, May 13 Lab #3 Scores are posted Pick...

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1 Tuesday, May 13 Lab #3 Scores are posted Pick up Homework #3 (problems 1 – 6 only) Solutions are posted Due date is  Thursday (5/15)  before exam Lab #4 Due Friday Program #1 Grading is in progress Program #2 Will be posted soon Midterm #2 Thursday (5/15) in class
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2 Today's Topics More about the Internet Protocol (IP) Protocols, addressing, routing Fragmentation Midterm #2 Review
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3 Address masks To identify destination network, apply  address mask  to  destination address  and compare to  network address  in  routing  table   Use Boolean  and   if ((Mask[i] D) == Dest[i]) forward to NextHop[i]
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4 IP address classes Class A, B and C are  primary classes   Used for ordinary host addressing  Class D is used for multicast, a limited form of broadcast  Internet hosts join a multicast group  Packets are delivered to all members of group  Routers manage delivery of single packet from source to all members of multicast  group  Used for multicast backbone  Class E is reserved 
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5 What if the form doesn't fit? Large organizations may not be able to get as many addresses  in the Internet as they need  Example - UPS needs addresses for  millions  of computers  Example – School needs 6000 hosts Too big for class C, too many wasted addresses for class B
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6 Possible solutions Classless addressing  allow division between prefix and suffix at any bit boundary Sharing an IP address Use one IP address for multiple hosts
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7 Classless Addressing Example 128.193.47.25 dotted decimal 80 C1 2F 19 hexadecimal 1000 0000 1100 0001 0010 1111 0001 1001  binary This can be “re-aligned” to use variable-size prefixes and suffixes. Example: Suppose we want a 22-bit prefix and a 10-bit suffix
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8 Example: 1000 0000 1100 0001 0010 1111 0001 1001   Logical AND with a " mask " using 22 bits for prefix ( netmask ), 10  bits for suffix: 1111 1111 1111 1111 1111 1100 0000 0000 … gives a prefix: 1000 0000 1100 0001 0010 11 00 0000 0000 The complement mask ( hostmask ) 0000 0000 0000 0000 0000 0011 1111 1111 … gives a suffix: 0000 0000 0000 0000 0000   00 11 0001 1001
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9 Example: 1000  0000 1100  0001 0010 11 00 0000 0000 0000 0000 0000 0000 0000   00 11  0001 1001 i.e., the “network number” is 80C12C00h, and the “host number”  within the network is 319h With 10 bits for suffix, 1024 host addresses are available within  the subnet (but 2 of these are reserved) Address still looks almost the same in dotted decimal 128.193.47.25  / 22 Additional information is provided so addressing can be handled by  routers
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This note was uploaded on 06/28/2009 for the course CS 372 taught by Professor Leviet during the Fall '07 term at Oregon State.

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Lecture13 - Tuesday, May 13 Lab #3 Scores are posted Pick...

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