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CS 1150 – Lab #15 –
Networking
TA – Sanjaya Wijeratne
E-mail – [email protected]
Web Page - http://knoesis.org/researchers/sanjaya/
TA Labs, Office Hours Laboratory Polices
• Lab Hours
• 2:30 PM - 4:20 PM, Monday at Room 320 - Oelman Hall
• TA Office Hours
• 4:45 PM - 5:45 PM, Monday at Room 316 - Russ Engineer Center
• By appointment – Please email to [email protected]
• Refer to CS 1150 Course Syllabus for Class and Laboratory Policies
• Zero tolerance policy for Academic Misconduct – All parties will get 0% marks
CS 1150 – Lab 15 – Networking
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Lab # 15 Overview
• Study how networks route packets to various destinations
• Learn how networks ensure reliable delivery
• Read all lab activities before attempting exercises
• Answer all questions in Exercises 1, 2, 4 and 5
• Lab #15 Due Date - Apr 14, 2014 11:55 AM
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How to Submit Lab #15
• Hard copy (Preferred)
• When you complete, hand it over to me
• Pilot
• Go to Pilot Course Page and Use Dropbox Submission Link to upload your files
• My Mailbox at CS Department
• Go to CS Department Front Desk and ask them to put your assignment in my mailbox
– Please write my name on your assignment (TA – CS 1150 – Sanjaya Wijeratne)
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What is a Computer Network?
• Group of computers (2 or more) that are connected together
to share data
• Eg – Internet
• Connections between computers in a network can be physical
using cables/wires or wireless via radio waves
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Network Protocols
• Protocol is a set of rules that governs a particular task. A
network protocol governs how computers communicate in a
network.
• TCP/IP
• Transmission Control Protocol – Reliable Communication
• IP – Addressing
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Network Topology
• Network Topology is the arrangement of different elements
in a computer network.
• Bus
• Star
• Ring
Source – http://en.wikipedia.org/wiki/Network_topology
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Routing in a Network
• Each node in the network has a routing table
• Routing table keeps track of
• What are the other nodes directly connected to a given node
• What routes to take if a node is not directly connected to the given
node
Source – http://en.wikipedia.org/wiki/Hop_(networking)#Next_hop_forwarding
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TCP/IP Applet
• TCP/IP applet simulates a reliable communication between
two nodes (computers) in a network
• DAT – Data packet
• ACK – Acknowledgement that data was received without errors
• NAK – Negative Acknowledgement which says there was an error
in data receiving.
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TCP/IP Applet Cont.
Data
Packet
• DAT 1 0 221
• 1 – Destination Address
• 0 – Sequence Number
• 221 – Checksum
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TCP/IP Applet Cont.
• ACK 0 1 0
ACK
Packet
CS 1150 – Lab 15 – Networking
• 0 – Destination Address
• 1 – Sequence Number
• 0 – Checksum
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TCP/IP Applet Cont.
• NAK 0 1 0
NAK
Packet
CS 1150 – Lab 15 – Networking
• 0 – Destination Address
• 1 – Sequence Number
• 0 – Checksum
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Exercise 1 – Q4 Help
• DAT 0 x xxx / ACK 1 x xxx – Consider all DAT and ACK
messages (headers) have 9 Characters
• All DAT messages can carry up to 10 characters of data
(payload)
• Your answer to this question should be 160. Show me the
steps to get marks.
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Exercise 1 – Q5 Help
• Use the following formula to calculate overhead
Total No. of Characters Exchanged – Total No. Characters in Message
Total No. of Characters Exchanged
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x 100
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Exercise 1 – Q6 Help
• How many DAT packets are needed to transfer 1,000,000
characters? (One DAT packet can carry 10 characters)
• Each DAT packet will contain overhead of 9 characters per
each message in addition to actual message content
• Each ACK packet will contain overhead of 9 character and
no message content
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Exercise 4 Help
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Exercise 4 Q5 and Q7
• Q5 – You need to write the answer and attach a
screenshot. Both answer and screenshot need to be
there to get full marks for this question
• Q7 – Attach a screenshot, no need to write by hand
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Additional Help
• Chapter 15 of Course Text Book – Communications Layer
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Questions ?
If you have questions, please raise your
hand, Colin or I will come to help you
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