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CS2200 Intro to Systems and Networks Homework 5 - Networking
Part I: The OSI Model
A.[14 points] Describe the purpose of each layer in the OSI model.Part II: Basic Networking Concepts
A. [10 points] Assume that packets have a header that is 16 bytes long and a payload of 32 bytes. If you wish to send a message that is 1024 bytes long. How many packets will be required? How many bytes in total will need to be sent?B. [10 points] Given these parameters:
| wire bandwidth | 15Mbps (15 x 10^7 bits per second), full-duplex |
| time-of-flight | 25ms (25 x 10^-3 seconds) |
| sender overhead | 200us (200 x 10^-6 seconds) |
| receiver overhead | 200us (200 x 10^-6 seconds) |
What's the effective bandwidth if you send an endless sequence of 10000-bit messages. Endless as in the sender never waits for ACKs? (Hint: Each packet must have the time for sender overhead included.)
Part III: Short Answer Questions
(Part A, 10 Points) The transport layer usually handles cases where packets arrive out of order. What additional mechanism would our protocol require in order to handle out-of-order packets? (Your answer should be approximately two words long).(Part B, 5 Points) ntohl() and htonl() are two UNIX C functions. Briefly describe what they do and why they are needed when sending numbers over a mixed network.
(Part C, 5 Points) For each of the following, specify whether it is big-endian or little-endian:
- Linux (x86)
- SPARC
- Windows (x86)
- Java Virtual Machine
- Network Order
Part IV: Networking Hardware
A.[12 points] Describe the function of each of the following devices and the layer at which they operate: NIC, Hub, Repeater, Bridge, Switch, RouterPart V: The MAC layer
A.[12 points] Explain how the Ethernet protocol worksB.[12 points] Explain the difference between CSMA/CD and CSMA/CA. Why is the latter used in some circumstances?
C.[10 points]) What is RTS/CTS and explain its use in the MAC layer.