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CSCI 4171 > Midterm > Flashcards

Midterm Flashcards

1
Q

What is a two-node point-to-point topology and its attributes?

A

Two nodes, connected with a link.

  • Simple topology
  • Can serve as a building block for other topologies
  • Also used in WAN point to point connections
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2
Q

What is a linear topology and its drawbacks?

A
  • Multiple point-to-point connections in a linear fashion.
  • Drawbacks:
    • Data transfer between nodes may need to go through other nodes
    • Poor fault tolerance
    • Link bandwidth may not be well utilized
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3
Q

What is a bus topology? What is a problem and a solution

A
  • Linear topology, but all nodes share a common link
  • Better utilization, However:
    • Transmission may collide
    • Solution: Medium access control (CSMA/CD)
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4
Q

What are traditional/classical Ethernets (topology) based on?

A

Bus topology

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5
Q

What is a ring topology?

A
  • Multiple nodes share a single link connected as a ring
  • Orderly transmission without collision by token passing mechanism
    • Special bit pattern circulating around the ring
    • Only a node that ‘captures’ the token can send a message
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6
Q

What is the token in a token ring topology?

A

A special bit pattern that allows a node to send a packet.

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7
Q

What is a dual ring topology ( FDDI Network)?

A

Two opposing token ring topologies.

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8
Q

What is a star topology?

A
  • Multiple nodes connected to a central hub
  • Hub is like a collapsed bus - serves the same function –> data broadcast to all nodes.
  • Has better fault tolerance than the bus topology
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9
Q

What type of topology is the CS building? Why?

A

A star topology.

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10
Q

What is a mesh topology?

A
  • Multiple point-to-point links connected in an arbitrary topology
  • Can be a full mesh (all nodes connected) or partial mesh (some links not present)
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11
Q

What is used for simple length extension?

A

repeater/hub

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12
Q

What is used for length extension and filtering

A

switch/bridge

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13
Q

What is used for extension + filtering and Interconnection of two topologies

A

Router

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14
Q

What is used for the interconnection of two different protocols (e.g. tcp/ip to DECNet)?

A

gateway

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15
Q

What is the main difference between a router and gateway?

A
  • A gateway is for two different protocols and router is for different topologies.
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16
Q

How does the traceroute utility work?

A

ICMP protocol, TTL set to 1 and increments the value.

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17
Q

How does circuit switching works?

A
  • A dedicated physical circuit or path is established between the source and destination.
  • The circuit or path remains in place for the duration of the communication.
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18
Q

What are the advantages of circuit switching?

A
  • Dedicated path
  • Bandwidth guarantee for the entire duration
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19
Q

What are the drawbacks of circuit switching?

A
  • Bandwidth cannot be shared
  • Unused bandwidth is essentially wasted
  • Message cannot be rerouted (faults or congestion)
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20
Q

How does message switching work?

A
  • Each message is stored and forwarded from node to node
  • No dedicated path or circuit is established
  • Receiver need not be aware/ready to accept the communication
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21
Q

What are the advantages of message switching?

A
  • No dedicated path –> better bandwidth utilization
  • Paths can be shared –> unused bandwidth != to wasted bandwidth
  • Messages can be rerouted
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22
Q

What are the drawbacks of message switching?

A
  • Long messages can be an issue (exceed buffer)
  • Link failure is network expensive (lose a whole message during transmission)
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23
Q

What is datagram packet switching?

A
  • True packet switching
  • Each packet is an independant independent entity - may be routed along different paths.
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24
Q

What are the advantages of datagram packet switching?

A
  • No dedicated path
  • No long messages
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25
Q

What are the disadvantages of datagram packet switching?

A
  • Time overhead
  • Space overhead
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26
Q

What is virtual packet switching?

A
  • Hybrid of circuit switching and packet switching
  • A route is established and all packets follow the same route.
  • A route is a not a dedicated path
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27
Q

What are the advantages virtual packet switching?

A
  • No dedicated path
  • Reduce time overhead
  • Reduce space overhead
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28
Q

What are the drawbacks virtual packet switching?

A
  • Extra cost in routers to maintain tables
  • In the case of a fault, the whole connection needs to be reestablish
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29
Q

What is the port number of FTP?

A

20 and 21

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30
Q

What is the port number of SSH?

A

22

31
Q

What is the port number of HTTP?

A

80

32
Q

What is the port number of telnet?

A

23

33
Q

What is bandwidth?

A
  • The capacity of a link, or the amount of data that can be carried by a link per sec
  • bits/sec
  • Depends on link technology
34
Q

What is delay?

A
  • Time is taken for a message entity (a packet) to travel from source to destination
  • Nodal delay (node-to-node)
35
Q

What is the nodal delay formula?

A

processing delay + queueing delay + propogation delay + transmission delay

36
Q

What is Tproc (processing delay) and formula?

A
  • Time to examine a packet header
  • Depends on hardware
37
Q

What is transmission delay and the formula?

A
  • Time to push the packet onto to the link
  • Depends on the bandwidth of the link
  • L/B (L length of the packet in bits, bandwidth in bits/sec)
38
Q

Formula for Propagation delay (Tprop)

A

Distance/speed

39
Q

What is the formula of traffic intensity?

A
  • Length of packet
  • the average arrival of packets (packets per sec)
  • Bandwidth
  • La/B
40
Q

What are the five layers of the TCP/IP stack (top to bottom)

A
  • Application
  • Transport
  • Network
  • Data link
  • Physical
41
Q

Describe the application layer of the TCP/IP stack and example services.

A
  • Allows the user to access the network
  • Services:
    • FTP
    • Mail services
    • Directory services
    • Network management
    • Remote access
  • Data compression
  • Encryption
42
Q

Describe the transport layer of the TCP/IP stack.

A

End to end transfer between hosts

  • Segmentation and reassembly
  • Connection control
  • Flow control
  • Error control
43
Q

Describe the network layer of the TCP/IP stack.

A
  • Concerned with delivery across multiple networks
  • Path determination and routing are the main functions
  • Uses logical addressing (e.g. IP addresses)
44
Q

Describe the data link layer of the TCP/IP stack.

A
  • Medium access control
    • Techniques to regulate access to a link
  • Error detection and control
    • Frame reliability
  • Flow control
    • Regulates flow of frames
  • Uses physical addressing
    • Addressing on a network (e.g. MAC address)
45
Q

Describe the physical layer of the TCP/IP stack.

A

Interface to the link

  • Bits to signal conversion and vice versa
  • Defines bit representation and data rates
  • Defines characteristics of the device and the link
46
Q

What are examples of application layer protocols?

A
  • HTTP
  • FTP
  • TFTP
  • SNMP
  • NFS
  • Telnet
  • SSH
  • DNS
  • BGP
47
Q

What are examples of transport layer protocols?

A
  • TCP
  • UDP
48
Q

What are examples of network layer protocols?

A
  • IP
  • ICMP
  • IGMP
  • ARP
  • RARP
  • RIP
  • RGIP
  • EIGRP
  • OSPF
49
Q

What are examples of data link layer protocols?

A
  • IEEE 802.3, 802.5, 802.11
  • SLIP
  • PPP
  • FR
  • AIM
50
Q

What are examples of physical layer protocols?

A
  • IEEE 802.3, 802.5, 802.11
  • SLIP
  • PPP
  • FR
  • AIM
51
Q

What are the all encapsulated elements of a frame (left to right)?

A
  • source MAC
  • next node
  • source IP
  • destination IP
  • Source port number (over 49,152 to 65,535)
  • Destination port
  • Data
52
Q

What are the elements of a TCP header?

A
  • Port numbers
  • Sequence numbers
  • ACK numbers
  • Header length
  • Flags
  • Window size
  • Checksum
  • Urgent pointer
  • Options
53
Q

What is the size of every ‘row’ in the TCP header?

A

32 bits

54
Q

What is contained in the IP header?

A
  • IP version
  • Header length
  • Type of service
  • Total length
  • Fragment ID
  • TTL
  • Protocol
  • Source and destination address
  • Options
55
Q

What is a twisted pair cable?

A

Two insulated copper conductors twisted together in pairs

56
Q

What is the purpose of ‘twisting’ twisted pair cables?

A
  • Reduces electromagnetic interference from external sources such as crosswalk between neighbouring pairs
  • Reduces radiation emitted from the pairs.
57
Q

What is the quality determinant of a twisted pair capable?

A
  • The number of twists/inch
58
Q

What is a coaxial cable?

A

A shielded copper wire

59
Q

What is the skin effect? How do you prevent it?

A
  • Power dissipation on the outer surface can cause signal attenuation (a phenomenon known as “skin effect”.
  • Shield the cable
60
Q

What is a fiber optic cable? Structure? How does blank travel through an optical cable?

A
  • A cable that transmits signals in the form of light beam
  • Structure:
    • Outer jacket of Teflon or PVC
    • Kevlar fiber for protection
    • Plastic coating to cushion the fiber
    • Central optical cable made of glass/plastic material
61
Q

How do wireless transmissions work? What is the unit of measurement?

A
  • Transmission of signals as electromagnetic waves in free space
  • Frequency in Hertz (Hz)
62
Q

What frequency encompasses most wireless frequencies (wireless and LAN)?

A

800 KHz - 5GHz range

63
Q

What type of link has digital data and digital transmission?

A

Ethernet

64
Q

What type of link has digital data and analog transmission?

A

WiFi and Dialup

65
Q

What type of link has analog data and analog transmission?

A

Telephone

66
Q

What type of link has analogue data and digital transmission?

A

VoIP and Digital Telephony

67
Q

Describe the components of the cable specification: X BASE/BROAD Y

A
  • X bandwidth in Mbps
  • Baseband digital
  • Broadband analog
  • Y is the distance in 100m or type
68
Q

What is 100 BASE 5?

A
  • 100 Mbps
  • Digital
  • 500 meters
69
Q

What is 10 BASE 2?

A
  • 10 Mbps
  • Analog
  • (2 x 100m) 200m
70
Q

What is the type TX?

A

UTP or twisted pair

71
Q

What is the type FX?

A

Fiber

72
Q

1000 BASE TX?

A
  • 1000 Mbps
  • Baseband (digital)
  • Twisted pair or UTP
73
Q

1000 BASE FX?

A
  • 1000 Mbps
  • Digital (baseband)
  • Fiber

CSCI 4171 (2 decks)

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