CS 610 Computer Networks
Assignment # 04
FALL 2011
Total Marks = 20
Deadline
Your assignment must be uploaded / submitted before or on January 10, 2011
Upload Instructions
Please view the assignment submission process document provided to you by the
Virtual University of Pakistan
Rules for Marking
Please note that your assignment will not be graded if:
• It is submitted after due date.
• The file you uploaded does not open.
• The file you uploaded is copied from someone else or from internet.
• It is in some format other than .doc
Objective
The assignment has been designed to develop the understanding about the concept of
Datagram transmission and Internet Control Message Protocol.
Note: Material that is an exact copy from handouts or internet would be graded
zero marks. Your solution should consist of the material found through different sources and written in your own words.
Assignment Statements:
Q1. If the application selects a datagram size greater than MTU along the path to the destination. How to handle this situation? Illustrate your answer with your own words.
Q2: How can ICMP be used for automated tool and Path discovery? Illustrate your answer with your own words.
Assignment # 4 Solution cs610
ReplyDeleteQ1. If the application selects a datagram size greater than MTU along the path to the destination. How to handle this situation? Illustrate your answer with your own words.
Sol:MTU:
Every hardware technology specification includes the definition of the maximum size of
the frame data area, which is called the Maximum Transmission Unit (MTU). Any
datagram encapsulated in a hardware frame must be smaller than the MTU for that
hardware.
FRAGMENTATION:
One technique is to limit datagram size to smallest MTU of any network. IP uses
fragmentation i.e. datagrams can be split into pieces to fit in network with small MTU.
Router detects datagram larger than network MTU and then it splits into pieces and each
piece is smaller than outbound network MTU.
Each fragment is an independent datagram. It includes all header fields. Bit in header
indicates that the datagram is a fragment. Other fields have information for reconstructing
original datagram. Fragment offset gives original location of fragment.
Router has local MTU to computer size of each fragment. It puts part of data from
original datagram in each fragment and puts other information into header.[FONT='Trebuchet MS', Trebuchet, 'Lucida Sans Unicode', 'Lucida Grande', Arial, sans-serif]
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Q2: How can ICMP be used for automated tool and Path discovery? Illustrate your answer with your own words.Sol:AN ERROR REPORTING MECHANISM (ICMP)
INTRODUCTION:
IP provides best-effort delivery. Delivery problems can be ignored; datagrams can be
‘dropped on the floor’. Internet Control Message Protocol (ICMP) provides error
reporting mechanism.INTERNET CONTROL MESSAGE PROTOCOL:
Some errors can be reported. Router sends message back to source in datagram. Message
contains information about problem. It is encapsulated in IP datagram.USING ICMP TO TEST REACHABILITY:
ICMP can also be used to test different tools. An Internet host A, is reachable from
another host B, if datagrams can be delivered from A to B. Ping program tests reachability.
It sends datagram from B to A, that echoes back to B. it uses ICMP echo request
and echo reply messages. Internet layer includes code to reply to incoming ICMP echo
request messages.USING ICMP FOR PATH MTU:
Fragmentation should be avoided. Source can configure outgoing datagrams to avoid
fragmentation. Source determines path MTU- smallest network MTU on path from
source to destination. Source probes path using IP datagrams with don’t fragment flag.
Router responds with ICMP fragmentation required message. Source sends smaller
probes until destination reached.
Read more: CS610 Assignment No 4 Solution & Discussion Due Date: 10-01-2012 - Virtual University of Pakistan http://vustudents.ning.com/group/cs610computernetwork/forum/topics/cs-610-computer-networks-assignment-04#ixzz1j3NApe8q