Homework3

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Author:
erika01
ID:
111812
Filename:
Homework3
Updated:
2011-10-24 16:47:48
Tags:
Kumar CNP
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Problems and Solutions
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  1. Find all the Fragments and Field Values for Fragment Headers in Slide 20 of our notes.

    Original Datagram (=Packet) = 404 Octets/Bytes
    Offset = 0
    More = 0

    Fragment (Data+IP Header=Payload) Limit = 208 Bytes
    With a minimum 20 bytes Header Size
    • *IMPORTANT: Offset calculation is done on the Data Payload ONLY!!!
    • --> Offset = Payload / 8

    Original datagram payload = Data(384bytes) + Header(20bytes)

    • 1st Fragment:
    • Length = 208 Bytes
    • Offset = 0
    • More = 1

    • 2nd Fragment:
    • Length = 208 Bytes
    • Offset = (208-20)/8 = 23.5 bytes
    • More = 1

    • 3rd Fragment:
    • Payload = (384 - (188+188)) = 8bytes left
    • = 8 + 20 = 28bytes
    • Length = 28 bytes
    • Offset = 8(payload) / 8 = 1
    • More = 0
  2. An IP Datagram of length 4326 Bytes needs to be sent on a LAN (Local Area Network) that uses CSMA/CD Protocol. How many fragments will need to be sent for this original IP Datagram? Mention all needed fields for all resulting fragments
    • Original Datagram (=Packet) = 4326 Bytes
    • Max Payload of Ethernet = 1500 Bytes
    • Max IP packet size = 1500 = Data(1500-20 = 1480 bytes) +Header(20 bytes)

    • 1st Fragment:
    • Length = (1480+20) = 1500 bytes
    • Offset = 0
    • More = 1

    • 2nd Fragment:
    • Length = 1500 bytes
    • Offset = (1500 - 20)/8 = 185 bytes
    • More = 1

    • 3rd Fragment:
    • Length = 4306(original) - 1480 - 1480 = 1346bytes
    • = 1346 + 20 = 1366 bytes
    • Offset = 4326(original)-1346(length)=2980
    • = (2980 - 20) / 8 = 370 bytes
    • More = 0
  3. Find the Number of Networks and Number of Hosts that can be supported by a Class A, Class B and Class C (used for unicast) IP Address Type.
    • Clss | Lft Bits | NetID | HostID | #Networks | #Hosts
    • A 0xxx 8 24 ~27 (-2) ~224 (-2)
    • B 10xx 16 16 ~214 (-2) ~216 (-2)
    • C 110x 24 8 ~221 (-2) ~28 (-2)
  4. Read RFC-791, RFC-1071 and RFC-790. What are they, what is their significance?
    • RFC-791 refers to the Internet Protocol (IP): Forwarding and Addressing in the Internet, focusing on IPv4. It revises aspects of addressing, error handling, option codes, and the security,
    • precedence, compartments, and handling restrictions features of the Internet
    • Protocol.

    • RFC-1071 refers to the computing
    • of Internet Checksum that is used by the standard Internet protocols IP, UDP,
    • and TCP. It informs about the techniques and algorithms for efficiently
    • computing the Internet Checksum, considering that the efficiency of checksum
    • implementation is critical to a good performance.

    • RFC-790 refers to the Assigned
    • Network Numbers/Assigned Numbers. This Network Working Group Request for
    • Comments documents the currently assigned values from several series of numbers
    • used in network protocol implementations.

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