Chapter 8 - Test 3 Flashcards Preview

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Flashcards in Chapter 8 - Test 3 Deck (81):
1

What are the four types of WAN services?

-circuit-switched
-dedicated circuit
-packet-switched
-virtual private network.

2

Describe common carriers.

-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.

3

Describe local exchange carriers.

-common carriers that provide local telephone services.

4

Describe local exchange carriers.

-common carriers that provide local telephone services.

5

Describe interexchange carriers(IXCs).

-common carriers that provide long-distance services.

6

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

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

7

Describe circuit-switched networks.

-Oldest and simplest approach to WAN circuits.
-operate over the public switched telephone network(PSTN)

8

What architecture do circuit switched services use?

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

9

How do circuit-switched services operate?

-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.

10

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

-POTS and ISDN

11

Describe POTS.

-Plain old telephone service
-dial up services
-use telephone line and a modem.
-33 kbps to 56 kbps data rate.

12

Describe ISDN

-integrated services digital network
-combines voice, video and data over the same digital circuit.
-original= narrowband ISDN.

13

How does ISDN work?

-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)

14

How does ISDN work?

-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.

15

Describe Basic rate interface(BRI).

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

16

Describe Primary rate interface(PRI).

-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).

17

What are two problems with circuit-switched networks?

-need separate connection for each connection.
-data rates are slow ranging from 56Kbps to 128 Kbps or 1.5Mbps

18

Describe dedicated-circuits.

-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.

19

what type of connections are dedicated connections?

-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.

20

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

-multiplexers or channel service unit (CSU)
-and/or a data service unit(DSU.
-equivalent of a NIC in a LAN.

21

how are dedicated circuits billed?

-flat fee per month
-user has unlimited use of the circuit.

22

What are the three basic dedicated-circuit network architectures?

-ring, star, mesh.

23

What is a distributed star architecture?

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

24

Describe a ring architecture.

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

25

What are disadvantages to the ring architecture?

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

26

What happens if there is a failure?

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

27

Describe the star architecture.

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

28

Describe the star architecture.

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

29

What are the advantages of a star topology?

-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.

30

What are disadvantages to the star network?

-susceptible to traffic problems because one computer processs all the messages on the network.
-central computer fails, entire network fails.

31

What are disadvantages to the star network?

-susceptible to traffic problems because one computer processs all the messages on the network.
-central computer fails, entire network fails.

32

Describe a dedicated-circuit mesh architecture.

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

33

What is the advantage of mesh networks?

-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

What is a drawback of mesh networks?

-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

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

-T carrier services
-Synchronous optical network(SONET services.
-each has their own data link protocols.

36

Describe T-carrier services.

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

37

Describe a T1 service.

-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

Describe a T3 circuit.

-transmission rate of 44.736 Mbps.
-equals capacity of 28 T1 circuits.
-popular for corporate MANs and WANs.

39

Describe Fractional T1

-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

Describe Fractional T1

-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

Describe SONET.

-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

Describe SONET.

-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

Describe packet-switched networks.

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

44

How doe packet-switched services work?

-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

What is a PAD?

-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

What are the advantages of packet-switched networks?

-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

What are the advantages of packet-switched networks?

-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

Describe datagram.

-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

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

-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

Describe a PVC.

-permanent virtual circuit
-defined for frequent and consistent use by the network.
-do not change unless the network manager changes the network.

51

Describe a PVC.

-permanent virtual circuit
-defined for frequent and consistent use by the network.
-do not change unless the network manager changes the network.

52

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

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

53

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

-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

What can potentially happen to packets above CIR?

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

55

Describe POP

-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

What are the four types of packet switched services?

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

57

Describe ATM.

-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

How does ATM work?

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

59

What is ATM considered?

-unreliable packet service
-no error control in the network
-responsibility is on source and destination.

60

What else does ATM provide?

-extensive QoS information enables setting very precise priorities.
-scalable: easy to multiplex basic ATM circuits into faster circuits.

61

Describe Frame relay.

-transmits data slower than ATM, sometimes called "poor man's ATM"

62

How does frame relay work?

-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

How does frame relay work?

-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

Describe ethernet services.

-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

Describe MPLS.

-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

How does MPLS work?

-customer connects to common carrier's network.
-carrier's switch converts incoming layer 2 or 3 address into an MPLS address label.

67

What is an advantage of MPLS?

-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

What is an advantage of MPLS?

-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

Describe a VPN.

-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

How do VPNs work?

-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

How do VPNs work?

-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

Describe VPN software.

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

73

Describe layer-2 VPNs.

-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

Describe layer-3 VPNs.

-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

What are the advantages of VPNs?

-low-cost and flexibility.

76

Describe an extranet VPN?

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

77

Describe an access VPN.

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

78

Describe an access VPN.

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

79

Describe an ESP.

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

80

Describe an ESP.

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

81

Describe latency.

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