CS 1150 – Lab #15 – NetworkingTA – Sanjaya Wijeratne

E-mail – wijeratne.2@wright.eduWeb Page - http://knoesis.org/researchers/sanjaya/

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TA Labs, Office Hours Laboratory Polices

• Lab Hours• 2:30 PM - 4:20 PM, Monday and Friday at Room 320 - Oelman Hall

• TA Office Hours• 4:40 PM - 5:40 PM, Monday and Friday at Room 316 - Russ Engineer Center• By appointment – Please email to wijeratne.2@wright.edu

• 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 - Nov 22, 2013 12:30 PMCS 1150 – Lab 15 – Networking

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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 into

my mailbox – Please write my name on your assignment (TA – CS 1150 – Sanjaya Wijeratne)

CS 1150 – Lab 15 – Networking

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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

CS 1150 – Lab 15 – Networking

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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

CS 1150 – Lab 15 – Networking

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Network Topology

• Network Topology is the arrangement of different elements in a computer network.• Bus• Star• Ring

CS 1150 – Lab 15 – Networking

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

CS 1150 – Lab 15 – Networking

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.CS 1150 – Lab 15 – Networking

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TCP/IP Applet Cont.

CS 1150 – Lab 15 – Networking

Data Pack

et• DAT 1 0 221• 1 – Destination

Address• 0 – Sequence

Number• 221 – Checksum

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TCP/IP Applet Cont.

CS 1150 – Lab 15 – Networking

ACK Pack

et

• ACK 0 1 0• 0 – Destination

Address• 1 – Sequence

Number• 0 – Checksum

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TCP/IP Applet Cont.

CS 1150 – Lab 15 – Networking

• NAK 0 1 0• 0 – Destination

Address• 1 – Sequence

Number• 0 – Checksum

NAK Pack

et

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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 DAK 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.

CS 1150 – Lab 15 – Networking

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Exercise 1 – Q5 Help

• Use the following formula to calculate overhead

CS 1150 – Lab 15 – Networking

Total No. of Characters Exchanged – Total No. Characters in MessageTotal No. of Characters Exchanged

x 100

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Exercise 1 – Q6 Help

• How many DAT packets are needed to transfer 1,000,000 messages? (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

CS 1150 – Lab 15 – Networking

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Exercise 2 Help

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Additional Help

• Networks (Chapter 15) Slides by Ms. Karen Meyer discussed in Class• Chapter 15 of Course Text Book –

Communications Layer

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Questions ?

If you have questions, please raise your hand, Colin or

myself will come to help youCS 1150 – Lab 15 – Networking