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IS 3413 > Chapter 8 - Test 3 > Flashcards

Chapter 8 - Test 3 Flashcards

1
Q

What are the four types of WAN services?

A
  • circuit-switched
  • dedicated circuit
  • packet-switched
  • virtual private network.
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2
Q

Describe common carriers.

A
  • private companies such as att, Bell canada, Sprint, and BellSouth that provide communication services to the public
  • you do not lease physical cables, lease circuits that provide certain transmission characteristics.
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3
Q

Describe local exchange carriers.

A

-common carriers that provide local telephone services.

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4
Q

Describe local exchange carriers.

A

-common carriers that provide local telephone services.

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5
Q

Describe interexchange carriers(IXCs).

A

-common carriers that provide long-distance services.

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6
Q

What federal government agency regulates data and voice communications in the US?

A
  • Federal Communications Commission.

- Canada: Canadian Radio-Television and Telecommunications Commission(CRTC)

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7
Q

Describe circuit-switched networks.

A
  • Oldest and simplest approach to WAN circuits.

- operate over the public switched telephone network(PSTN)

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8
Q

What architecture do circuit switched services use?

A
  • cloud architecture.

- users lease connection points into the common carrier’s network which is called the clud.

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9
Q

How do circuit-switched services operate?

A
  • person dials telephone number of the destination computer and establishes a temporary circuit between the two computers.
  • computers exchange data and then the circuit is disconnected.
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10
Q

What are the two basic types of circuit-switched services?

A

-POTS and ISDN

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11
Q

Describe POTS.

A
  • Plain old telephone service
  • dial up services
  • use telephone line and a modem.
  • 33 kbps to 56 kbps data rate.
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12
Q

Describe ISDN

A
  • integrated services digital network
  • combines voice, video and data over the same digital circuit.
  • original= narrowband ISDN.
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13
Q

How does ISDN work?

A
  • telephone lines.
  • special equipmetn to connect their computers into PSTN.
  • ISDN network terminator that functions like a hub and a NIC(terminal adapter), also called an ISDN modem.
  • each computer attached to the NT-1/NT-2 needs a unique service profile identifier (SPID)
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14
Q

How does ISDN work?

A
  • telephone lines.
  • special equipmetn to connect their computers into PSTN.
  • ISDN network terminator that functions like a hub and a NIC(terminal adapter), also called an ISDN modem.
  • each computer attached to the NT-1/NT-2 needs a unique service profile identifier (SPID) to aidentify it.
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15
Q

Describe Basic rate interface(BRI).

A

-2B+D. provides a communication circuit with two 64 Kbps digitaion transmission channels and one 16 Kbps control signalling channel.

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16
Q

Describe Primary rate interface(PRI).

A
  • 23B+D. offered to commercial customers.
  • 23 64-Kbps B channels plus 1 64 Kbps D channe.
  • almost same capacity as a T1 circuit (1.544 Mbps).
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17
Q

What are two problems with circuit-switched networks?

A
  • need separate connection for each connection.

- data rates are slow ranging from 56Kbps to 128 Kbps or 1.5Mbps

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18
Q

Describe dedicated-circuits.

A
  • user leases circuits from the common carrier for his or her exclusive use 24 hours per day, 7 days per week.
  • also called private line services.
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19
Q

what type of connections are dedicated connections?

A
  • point to point
  • from one building in one city to another building.
  • carrier installs the circuit connections at the two end points of the circuit and makes the connection between them.
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20
Q

What type of equipment is included in dedicated-circuit networks?

A
  • multiplexers or channel service unit (CSU)
  • and/or a data service unit(DSU.
  • equivalent of a NIC in a LAN.
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21
Q

how are dedicated circuits billed?

A
  • flat fee per month

- user has unlimited use of the circuit.

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22
Q

What are the three basic dedicated-circuit network architectures?

A

-ring, star, mesh.

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23
Q

What is a distributed star architecture?

A

-series of star networks that are connected by a mesh or ring architecture.

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24
Q

Describe a ring architecture.

A
  • connects all computers in a closed loop with each computer linked to the next.
  • circuits are full-duplex or half-duplex.
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25
Q

What are disadvantages to the ring architecture?

A

-messages can take a long time to travel from the sender to the receiver resulting in traffic delayrs

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26
Q

What happens if there is a failure?

A

-traffic will be routed away from the failed circuit, but it will double the traffic.

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27
Q

Describe the star architecture.

A

-connects all computers to one central computer that routes messages to the appropriate computer.

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28
Q

Describe the star architecture.

A

-connects all computers to one central computer that routes messages to the appropriate computer.

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29
Q

What are the advantages of a star topology?

A
  • easy to manage because central computer receives and routes all messages in the network
  • faster because any message needs to travel through at most two circuits.
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30
Q

What are disadvantages to the star network?

A
  • susceptible to traffic problems because one computer processs all the messages on the network.
  • central computer fails, entire network fails.
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31
Q

What are disadvantages to the star network?

A
  • susceptible to traffic problems because one computer processs all the messages on the network.
  • central computer fails, entire network fails.
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32
Q

Describe a dedicated-circuit mesh architecture.

A
  • full-mesh: every computer is connected to every other computer. Extremely high cost.
  • partial-mesh: many but not all computers are connected.
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33
Q

What is the advantage of mesh networks?

A
  • combine the performance benefits of both ring and star networks.
  • mesh networks provide relatively short routes through the network and provide many possible routes through the network to prevent any one circuit or computer from becoming overloaded.
34
Q

What is a drawback of mesh networks?

A
  • use decentralized routing so that each computer in the network performs its own routing.
  • requires more processing by each computer in the network than in star or ring networks.
  • transmission o fnetwork status information wastes network capacity.
35
Q

What are the two types of dedicated circuit services in use?

A
  • T carrier services
  • Synchronous optical network(SONET services.
  • each has their own data link protocols.
36
Q

Describe T-carrier services.

A
  • most commonly used form of dedicated-circuits services in North America today.
  • costs are fixed amount per month
37
Q

Describe a T1 service.

A
  • also called a DS1 circuit.
  • data arate of 1.544 Mbps.
  • used to transmit both data and voice.
  • Inverse TDM provideds 24 64 Kbpos circuits.
  • enables 24 simultaneous voice channels.
38
Q

Describe a T3 circuit.

A
  • transmission rate of 44.736 Mbps.
  • equals capacity of 28 T1 circuits.
  • popular for corporate MANs and WANs.
39
Q

Describe Fractional T1

A

-FT1
-offers portions of a 1.544 Mbps T1 circuit for a fraction of its full cost.
-most common FT1 services provide 128, 256, 384, 512, and 768 Kbps.
DS0=64Kbps.

40
Q

Describe Fractional T1

A

-FT1
-offers portions of a 1.544 Mbps T1 circuit for a fraction of its full cost.
-most common FT1 services provide 128, 256, 384, 512, and 768 Kbps.
DS0=64Kbps.

41
Q

Describe SONET.

A
  • American standard(ANSI) for high-speed dedicated-circuit services.
  • OC-1: optical carrier level 1=51.84Mbps.
  • OC-3072
  • each level above OC-1 created by an inverse multiplexer.
42
Q

Describe SONET.

A
  • American standard(ANSI) for high-speed dedicated-circuit services.
  • OC-1: optical carrier level 1=51.84Mbps.
  • OC-3072
  • each level above OC-1 created by an inverse multiplexer.
43
Q

Describe packet-switched networks.

A

-enable multiple connections to exist simultaneously between computers over the same physical circuit.

44
Q

How doe packet-switched services work?

A
  • user buys a connection

- pays fixed fee for the connection based on type and capacity and is charged for the number of packets transmitted.

45
Q

What is a PAD?

A
  • packet assembly/disassembly device.
  • user’s connection into the network
  • owned and operated by the customer or by the common carrier.
  • converts sender’s data into the network layer and data link layer packets used by the packet network and sends them through the packet-switched network.
46
Q

What are the advantages of packet-switched networks?

A
  • different locations can have different connection speeds into the common carrier cloud.
  • PAD compensates for differences in transmission speed between sender and receiver.
  • allow packets from separate messages with different destinations to be interleaved for transmission.
47
Q

What are the advantages of packet-switched networks?

A
  • different locations can have different connection speeds into the common carrier cloud.
  • PAD compensates for differences in transmission speed between sender and receiver.
  • allow packets from separate messages with different destinations to be interleaved for transmission.
48
Q

Describe datagram.

A
  • connectionless services
  • adds a destination address and sequence number to each packet in addition to information about the data stream to which the packet belongs.
49
Q

Describe a virtual circuit routing method as it relates to packet-switched circuits.

A
  • packet-switched network establishes what appears to be one ended to end circuit between the sender and receiver.
  • all packets for that transmission take the same route over the cirtual circuit that has been set up.
50
Q

Describe a PVC.

A
  • permanent virtual circuit
  • defined for frequent and consistent use by the network.
  • do not change unless the network manager changes the network.
51
Q

Describe a PVC.

A
  • permanent virtual circuit
  • defined for frequent and consistent use by the network.
  • do not change unless the network manager changes the network.
52
Q

What’s the difference between PVC’s and dedicated circuits?

A

-PVC’s are software based instead of hardware circuits.

53
Q

What are the two types of data rates negotiated in PVCs?

A
  • committed information rate(CIR): data rate the PVC must guarantee to transmit.
  • maximum allowable rate(MAR): maixmum rate that the network will attempt to provide over and above the CIR.
54
Q

What can potentially happen to packets above CIR?

A

-marked as discard eligible(DE) and can be discarded if network becomes overloaded.

55
Q

Describe POP

A
  • point of presence
  • organizations usually lease a dedicated circuit to a packet-switched network point of presence.
  • POP is location at which the packet-switched network or any common carrier network connects into the local telephone exchange.
56
Q

What are the four types of packet switched services?

A

-ATM, frame relay IP/MPLS, and ethernet services.

57
Q

Describe ATM.

A
  • Asynchronous Transfer Mode.
  • works similar to ethernet and TCP/IP networks
  • uses different layer 2 and layer 3 protocols.
  • typically uses SONET at layer 2.
58
Q

How does ATM work?

A

-usually performs encapsulation, ethernet frames are surround by an ATM layer-3 packet and a sonet frame.

59
Q

What is ATM considered?

A
  • unreliable packet service
  • no error control in the network
  • responsibility is on source and destination.
60
Q

What else does ATM provide?

A
  • extensive QoS information enables setting very precise priorities.
  • scalable: easy to multiplex basic ATM circuits into faster circuits.
61
Q

Describe Frame relay.

A

-transmits data slower than ATM, sometimes called “poor man’s ATM”

62
Q

How does frame relay work?

A
  • performs encapsulation of packets so packets are delivered unchanged through the network
  • unreliable packet service.
  • checks for errors but discards them. No error control
63
Q

How does frame relay work?

A
  • performs encapsulation of packets so packets are delivered unchanged through the network
  • unreliable packet service.
  • checks for errors but discards them. No error control.
64
Q

Describe ethernet services.

A
  • bypass the PSTN by laying their own gigabit Ethernet fiber-optic networks in large cities.
  • committed information rate (CIR) of 1Mbps to 40Gbps. in 1 Mbps increments at a lower cost than traditional packet-switched networks.
65
Q

Describe MPLS.

A
  • multi protocol lable switching.
  • designed to work with a variety of commonly used layer-2 protocols.
  • inserts 4-byte header that contains its own information between the layer-2 and layer-3 IP packet.
66
Q

How does MPLS work?

A
  • customer connects to common carrier’s network.

- carrier’s switch converts incoming layer 2 or 3 address into an MPLS address label.

67
Q

What is an advantage of MPLS?

A
  • operates faster than traditional routing.
  • common carriers in US and canada have diffrenet way of charging for MPLS services, common to use full mesh design.
  • fewer hops and less time to reach destination.
68
Q

What is an advantage of MPLS?

A
  • operates faster than traditional routing.
  • common carriers in US and canada have diffrenet way of charging for MPLS services, common to use full mesh design.
  • fewer hops and less time to reach destination.
69
Q

Describe a VPN.

A
  • provides equivalent of a private packet-switched network over the public internet.
  • series of PVCs that run over the internet so that the network acts like a set of dedicated circuits over a private packet network.
70
Q

How do VPNs work?

A
  • lease an internet connection.
  • pay common carrier for the circuit and ISP for internet access.
  • connect a VPN gateway to each internet access circuit to provide access from your switches to the VPN.
  • create PVCs through the internet that are called tunnels.
71
Q

How do VPNs work?

A
  • lease an internet connection.
  • pay common carrier for the circuit and ISP for internet access.
  • connect a VPN gateway to each internet access circuit to provide access from your switches to the VPN.
  • create PVCs through the internet that are called tunnels.
72
Q

Describe VPN software.

A

-used on home computers or laptops to provide the same secure tunnels to people working from offsite.

73
Q

Describe layer-2 VPNs.

A
  • uses layer-2 packet to select the VPN tunnel and encapsulates the entire packet starting with the layer-2 packet.
  • L2TP: layer 2 VPN
74
Q

Describe layer-3 VPNs.

A
  • uses layer-3 packet(IP to select the VPN tunnel and encapsulates the entire packet starting with the layer-3 packet.
  • discards the incoming layer-2 packet and generates an entirely new layer-2 packet at the destination
  • IPsec is a layer 3 VPN.
75
Q

What are the advantages of VPNs?

A

-low-cost and flexibility.

76
Q

Describe an extranet VPN?

A

-VPN connects several different organizations, often customers and suppliers over the internet.

77
Q

Describe an access VPN.

A

-enables employees to access an organization’s networks from a remote location.

78
Q

Describe an access VPN.

A

-enables employees to access an organization’s networks from a remote location.

79
Q

Describe an ESP.

A
  • Encapsulating security payload.
  • encapsulates ip, tcp and http packet which then is itself encapsulated with another transport and network layer protocols.
80
Q

Describe an ESP.

A
  • Encapsulating security payload.
  • encapsulates ip, tcp and http packet which then is itself encapsulated with another transport and network layer protocols.
81
Q

Describe latency.

A

-speed of a device to convert input packets to output packets.

IS 3413 (11 decks)

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