CSC645/745

We're gona ACE this quiz and the rest of the quizzes! :p

=Review #1=

Question 1 - Define networking terms
'''1. Define the following terms: protocol, network, network structure, internetwork, network architecture, protocol hierarchy, layer, level-n protocol, level n-1 interface, physical medium, service primitives. '''


 * Protocol: A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event. It defines peer-to-peer communications.
 * Network:  1 distributed system where communications are connected, means to transfer messages (data) between components in a single distributed system
 * Network Structure:	How components are physically connected. Example media: twisted pair wire, fiber optic cable, microwave channel. Two flavors: Point-to-point and multiple access
 * Internetwork: Take any networks of any sort and combine it to become bigger networks where routers are used to configure these networks. Means to transfer messages (data) between networks (i.e. between components in different distributed systems). A specific set of networks connected by routers that are configured to pass traffic among any computers attached to networks in the set. Most internets use TCP/IP protocols.
 * Network architecture: The design of a computer network. A set of layers and corresponding protocols
 * Protocol hierarchy: We have different layers on top of the physical media for the client and server that are connected via peer to peer protocols.
 * Layer: Well defined collection of functions. Run-time entities perform the functions defined by each layer.
 * Level-n protocol: Peer-to-peer communication on the same level n. Logical description of what peer is doing.
 * Level n-1 interface: Communication connection between level n and level n-1 protocol.
 * Physical medium: Physical material capable of holding data (i.e. wire, magnetic tape).
 * Service primitives: Communication operations that steps through a transfer of data.

Question 2 - point-to-point vs. multiple access
'''2. What is the difference between point-to-point and multiple access networks? '''


 * Point-to-Point Networks:
 * A collection of links that are connected by nodes.
 * Able to send a transmition (data) from links to links from the source to the destination
 * Developed in 1960s~1970s
 * OSI/ISO standards
 * Have dedicated links between pairs of components.
 * Types: star, ring, tree, complete, irregular (most common)-> Impossible to do math analysis. Least discussed
 * ISSUE: Network topology (which pairs of components have links)
 * Multiple access networks:
 * Single shared communication channel
 * Types: Satellite/radio, ethernet, token ring
 * Ethernet: more for LAN. 1 to aparnet and 1 connected to ethernet
 * ARPANET: connection out of the network in Europe
 * TCP/IP Protocols
 * ISSUE: Channel allocation (who's turn it is to use the media).

Question 3 - internetwork vs. network
'''3. How is an internetwork different from a network? Why are both necessary? '''
 * Internetwork
 * Consists of various kinds of networks but connected using a router.
 * Uses the TCP/IP
 * Not ISO protocols.
 * Last 10yrs are ISO compliants.
 * Means to transfer messages (data) between networks (i.e. between components in different distributed systems). A set of networks connected by routers that are configured to pass traffic among any computers attached to networks in the set. Most internets use TCP/IP protocols.
 * Network:
 * A single distributed system where communications are connected.
 * means to transfer messages (data) between components in a single distributed system


 * why both are necessary
 * An internetworks allows for communication between two or more networks that can be of different infrustructures. It also allows for LANs to become WANs.

Question 4 - level n-1 interfaces
'''4. Why don't network architectures specify the level n-1 interfaces? '''

The network architectures do not specify the level n-1 interfaces because these are not visible "outside" of the computer executing the protocol code.

Question 5 - communication between levels
'''5.	Why isn't communication between peers on different levels allowed? '''

Communication isn't allowed between peers on different levels to avoid the mix up of code (spaghetti code). Make the programming for each level a much simplier task for the programmer and to allow each level to work more efficiently.

Each of the layer in the architecture have a peer-to-peer protocol to communicate with the same layer level. Each of this layers have APIs and interfaces that separates them. A change on a lower level of the network stack should not affect the APIs that are defined higher and thus does not need the developer to rewrite the calls to the APIs. The change should be seemless.

Quiz #1

Question 6 - purpose of the interface control information
'''6.	What is the purpose of the interface control information (ICI) added by the level n entity. Does this information get delivered to the remote level-n peer? '''

Interface control infromation is control information added by a peer (service user) for the peer on the layer immediately below (service provider) and is removed by that peer.

This infromation does not get delivered to the remote level n peer but the level immediately below that.

Question 7 - purpose of the header information
'''7.	What is the purpose of the header information added by the level n entity? Does this information get delivered to the remote level n peer? '''

The header contains control information added by the level n peer for the corresponding peer on the same peer on the same level.

The information does get delievered to the remote level n peer.

Question 8 - level N PDU and the level N+1 PDU
'''8.	What is the relationship between the level N PDU and the level N+1 PDU? '''


 * PDU (Protocol Data Unit)
 * Message locally sent between 2 peers on the same level.
 * Consists of a header and a SDU (Service Data Unit).


 * SDU (Service Data Unit)
 * Message that is passed down the protocol stack via a service access point from an upper layer peer for delivery to a remote peer.



Question 9 - Protocol
'''9.	What is a protocol? How is it defined? '''

A protocol is defined by the format of messages exchanged and the legal exchange of sequences. It defines peer-to-peer communication, logical description of what the peer is doing.

Question 10 - 4 classes of service primitives
'''10.	What are the four classes of service primitives? '''
 * 1) Request a service
 * 2) Indicate that request has arrived
 * 3) give Response to request
 * 4) Confirm that request arrived

Question 11 - service primitives and ISO/OSI standards
'''11.	How are service primitives used in the ISO/OSI standards? '''

Upper layer (service user) asks for service and lower layer (service provider) provides service. Both are connected through a service access point.



Question 12 - confirmed message delivery vs. unconfirmed message delivery
'''12.	What is the difference between confirmed message delivery and unconfirmed message delivery? '''


 * Confirmed Message Delivery
 * Request + Indication + Response + Confirmation


 * Unconfirmed Message Delivery
 * Request + Indication

Question 13 - sequence of service primitives for delivery of confirmed message
'''13.	Describe the sequence of service primitives used to implement delivery of a confirmed message. '''

A picture paints a thousand words ;)



Question 14 - sequence of service primitives for delivery of unconfirmed message
'''14.	Describe the sequence of service primitives used to implement delivery of an unconfirmed message. '''

Another 10,000 words ;)



Quiz #2

Question 15 - ISO/OSI Layers
'''15.	What are the seven ISO/OSI layers? Give a one sentence description of each layer. '''

"All People Seem To Need Data Processing." :p remember that sentence.


 * 1) Physical Layer: Transmission of bits on a single link.
 * 2) Data Link Layer: Error free transmission of packets on a single link
 * 3) Network Layer: End-to-End transmission of packets
 * 4) Transport Layer: End-to-End delivery of messages flow control
 * 5) Session Layer: Setup and manage end-to-end conversation between users, provide enhance data transport and dialog control
 * 6) Presentation Layer: Control syntax and semantics of information transmitted
 * 7) Application Layer: High level user services as well as high level generic services

Question 16 - Physical Layer
'''16.	Describe the major functions of the ISO/OSI physical layer. '''


 * Transmission of bits on a single link.
 * DTE-DCE Data Transfer.
 * Control Signal between devices.
 * Clocking signals: suncrhonize data flow and regulate bit rate.
 * Electrical Ground
 * Mechanical connectors (sockets and plugs).

Question 17 - Data Link Layer
'''17.	Describe the major functions of the ISO/OSI data link layer. '''

Error free transmission of packets on a single link (flow control, line coordination).

Question 18 - Network Layer
'''18.	Describe the major functions of the ISO/OSI network layer. '''

End-to-End transmission of packets (subnet control, routing, congestion control, accoounting, network interface/gateway).

Question 19 - Transport Layer
'''19.	Describe the major functions of the ISO/OSI transport layer. '''

End-to-End delivery of messages (manage communication bit pipes between process) flow control.

Question 20 - Session Layer
'''20.	Describe the major functions of the ISO/OSI session layer. '''

Setup and manage end-to-end conversation between users, provide enhance data transport and dialog control.

Question 21 - Presentation Layer
21.	Describe the major functions of the ISO/OSI presentation layer.

Control syntax and semantics of information transmitted (formatting, compression, encryption).

Question 22 - Application Layer
'''22.	Describe the major functions of the ISO/OSI application layer. '''

High level user services (virtual terminals, file transfer, email, etc) as well as high level generic services (remote operations, reliable delivery, etc).

Question 23 - TCP/IP Layers
'''23.	What are the four (five) TCP/IP layers? Give a one sentence description of each layer. '''
 * 1) Hardware Layer: Physical bit transport
 * 2) Hardware Interface Layer: Transmit datagrams over specific network using physical address to identify hosts
 * 3) Transport Layer: Provide communication from one machine to another.
 * 4) User Services Layer: Provide communication between users (processes).
 * 5) Application Layer: Choose style of tranport and transfer data. Messages of streams of data are exchanged between peers

Question 24 - Hardware Layer
24.	Describe the major functions of the TCP/IP hardware and hardware interface layers (0 and 1).


 * Layer 0: Physical bit transport
 * Layer 1: Transmit datagrams over a specific network using physical addresses to identify hosts.
 * Not Part of TCP/IP protocols

Question 25 - Transport Layer
'''25.	Describe the major functions of the TCP/IP transport (IP) layer. '''


 * Provide communication from 1 machine to another.
 * IP datagrams are exchanged between peers.


 * IP (Internet Protocol): Datagram delivery service.
 * ICMP (Internet Control Message Protocol): Handle Error and control information.
 * ARP (Address Resolution Protocol): Translate IP addresses into physical addresses.
 * RARP (Reverse Address Resolution Protocol): Translate physical addresses into IP Addresses.

Question 26 - User Services Layer
'''26.	Describe the major functions of the TCP/IP user services (TCP/UDP) layer. '''


 * Provide communication between users (processes).
 * Transport protocol packets are exchanged between peers.


 * TCP (Transfer Control Protocol) Layer
 * Reliable
 * Full-duplex
 * Stream connection between processes
 * Connection oriented.


 * UDP (User Datagram) Layer
 * Connectionless protocol between processes
 * Messages are not guranteed to arrive.

Question 27 - Application Layer
'''27.	Describe the major functions of the TCP/IP application layer. Why is this layer usually not included as part of the TCP/IP protocol stack? '''


 * Choose style of transport and tranfer of data.
 * Messages or streams of data exchanged between peers (user application processes).


 * Why is the application layer not part of TCP/IP protocol stack?
 * The application layer is the top layer of the TCP/IP protocol I don't know :p

Question 28 - TCP/IP Layer Vs. ISO/OSI Layering
'''28.	How is TCP/IP layering different from ISO/OSI layering? '''


 * TCP/IP
 * End-to-End Reliability
 * Locus of intelligent decision making
 * Hosts
 * Layering = Description of Functionality


 * ISO/OSI
 * Link level Reliability
 * Locus of intelligent decision making
 * Network IMP's
 * Layering = Blueprint for implementation

Question 29 - connectionless vs. connection-oriented service
'''29.	What is the difference between connectionless and connection-oriented service? '''
 * Connectionless service	
 * No logical connection established between peers before data exchange.
 * Message may arrive in any order (may not arrive at all).
 * Difficult to account for network resource utilization.
 * Connection-oriented service
 * Peer entities set up logical connection before data transfer.
 * During data transfer, all messages are delivered in order (usually guranteed to be delivered).

Question 30 - Define "-plex" terms
30.	Define the following terms: full duplex, half duplex, simplex 
 * Full duplex	: Data transfer in both directions at the same time.
 * Half Duplex	: Data transfer is both directions, but only 1 direction at a time.
 * Simplex	: Data transfer in only 1 direction.

Question 31 - Protocols
'''31.	Which protocols of TCP/IP are connectionless? Connection-oriented? Which layers of the ISO/OSI protocol are connectionless? Connection-oriented? '''


 * TCP/IP
 * Connectionless
 * Hardware (Layer 0) -- Service must be provided or emulated
 * Hardware Interface (Layer 1) -- Service must be provided or emulated
 * Layer 2 IP & Friends (ARP, ICMP, RARP)
 * Layer 3 UDP


 * Connection-Oriented
 * Layer 3 TCP


 * ISO/OSI Protocol Layers
 * Connectionless
 * MAC Layer
 * LLC Layer (Pass through MAC)
 * Transport Layer (Pass through MAC)
 * Session Layer
 * Presentation Layer
 * Application Layer


 * Connection-Oriented
 * Physical Layer
 * Data Link Layer
 * Network Layer
 * LLC Layer (Pass through MAC)
 * Transport Layer (Pass through MAC)

=Review #2 - Physical & Mac Layers=

Question 1 - major functions of physical layer
1. What are the major functions of the physical layer?


 * DTE-DCE Data Transfer
 * Control signals between devices
 * clocking signals: synchronize data flow & regulate bit rate
 * electical ground
 * mecanical connectors (sockets & plugs)

Question 2 - functionality of physical layer
2. How is the functionality of the physical layer defined?


 * The physical layer is connection-oriented and uses unconfirmed messages.

Question 3 - physical layer services
'''3. Are the physical layer services confirmed or unconfirmed? Explain your answer. '''


 * It is unconfirmed. There is only request and indication. No response or confirmation.

Question 4 - service primitives - data link layer
'''4. Describe the sequence of service primitives that the (data link) sender uses to transfer a sequence of packets. Describe the sequence of primitives that the (data link) receiver uses. '''

Question 5 - state changes of simplex - duplex communication
'''5. How are the state changes exhibited by the sender and receiver different for simplex and duplex communication? '''

Question 6 - manchester encoding
6. Why is Manchester Encoding useful?

Manchester code is a form of data communication line code in which each bit of data is signified by at least 1 voltage level transition.

Machester encoding is useful because the signal synchronizes itself. This minimizes the error rate and optimizes reliability.

Question 7 - manchester encoding
7. Give the manchester encoding for the following bit string: 0000011111010101111  



=Supplementary Questions on Physical Layer=

Question 1 - State Diagram
'''1. In the state diagram given in the class notes all legal state transitions are specified. If a state transition is not specified then it is not legal. Another way to represent this information is to have another state (the "error" state) with transitions labeled with each of the out-of-sequence primitives. Add this state to the state diagram. '''

Question 2 - State Diagram(Duplex)
'''2.The state diagram as given allows full duplex communication. Modify the state diagram from question 1 so that it only allows half-duplex communication. Modify the state diagram so that it only allows simplex communication (note: you will need one state diagram for the sender and another for the receiver). '''

Question 3 - Sequence of primitives
'''3.Which of the following sequences of primitives are legal? (Assume that one site is executing the sequence and that peer is initially in state 1.) Explain your answer clearly!
 * a. PH-Data.request
 * PH-Data.request
 * PH-Data.request
 * b. PH-Activate.request
 * PH-Activate.indication
 * c. PH-Activate.request
 * PH-Deactivate.request
 * d.PH-Activate.indication
 * PH-Data.indication
 * PH-Data.indication
 * PH-Deactivate.indication '''

Question 4 - Sequence of primitives
'''4.Given the following (legal) sequences of primitives, list the sequence of primitives that the corresponding peer will execute, assuming it is initially in state 1. What is the final state of both peers?'''


 * a. PH-activate.request
 * PH-data.request
 * PH-data.request
 * PH-deactivate.request


 * b. PH-activate.request
 * PH-activate.indication
 * PH-data.indication
 * PH-data.request
 * PH-deactivate.indication
 * PH-deactivate.request

QUIZ 3

Question 8 - mac layer service primitives
8. What are the service primitives supported by the MAC layer

Question 9 - 1 persistent"
'''9. What does "1 persistent" mean? Under what circumstances is this a reasonable policy to use? '''

Question 10 - CSMA/CD
10. Define CSMA/CD (explain all terms clearly)

Question 11 - random exponential backoff policy for collision resolution
'''11. Describe the random exponential backoff policy for collision resolution. What happens if the media is unable to deliver packets due to excessively heavy load (or a failure in the network interface)? '''

Question 12 - host sending message to another host
'''12. Explain in your own words what happens when a single host attempts to send a message to another host on an ethernet. '''

Question 13 - ethernet transmission
'''13. Explain in your own words what happens if two ethernet hosts attempt to transmit at EXACTLY the same time. '''

14. What is tau? How is it used in designing the ethernet protocol? 15. Explain in your own words what happens if two ethernet hosts attempt to transmit at an interval of slightly greater than two tau time units. 16. How is the minimum message size determined in the ethernet protocol? 17. Why is it necessary to fix the maximum  message size in the ethernet protocol? 18. How does the ethernet hardware detect errors in transmission? 19. Why are ethernets generally considered to be unsecure media? 20. Is ethernet technology appropriate for real time applications? Explain your answer clearly. 21. How does the system programmer access the Ethernet? What parts of the Ethernet protocol are visible to the programmer? 22. Describe the fields in an Ethernet frame. 23. How does thin wire ethernet differ from standard ethernet? 24. How are connections made to a thin wire ethernet? Is this more or less difficult than connecting taps/T-junctions to a standard ethernet? 25. What is 10base-T ethernet? 26. What are some examples of networking technologies OTHER than ethernet that have been used to build local networks? 27. How does gigabit ethernet technology differ from slower ethernet variants? '''