2.5 - WAN technologies

Question 1

Explain Dail-up and it’s speeds

Answer 1

The original copper-based analog using public switched telephone network (PSTN) aka (POTS). Up to 56 Kbp/s.

Question 2

Explain ISDN

Answer 2

Integrated Services Digital Network. A legacy copper-based network using POTS, breaking the transmission into two channel types: Circuit-switched B channel, and Packet-switched D channel.

Question 3

Explain DSL

Answer 3

Digital Subscriber Line. A copper-based connection that can use POTS to support multiple voice and data channels. The speeds are comparable to T1 or cable modems, but with degrading strength the farther you are from the Central Office.

Question 4

Explain ADSL

Answer 4

Asymmetrical DSL. Offers greater download speed than upload speeds.

Question 5

Explain SDSL

Answer 5

Symmetrical DSL. The speeds are the same, maxing at about 2 Mbit/s

Question 6

Explain VDSL

Answer 6

Variable DSL. Fastest speeds, up to 50-60 Mbit/s.

Question 7

Explain Cable Broadband

Answer 7

Uses coaxial cabling to carry TV signals. Speeds can reach up to 10 Gbp/s with fiber as a backbone.

Question 8

What is HFC?

Answer 8

Hybrid-fiber-copper. When fiber is used as a backbone and copper is used to connect the customer to that fiber line.

Question 9

Explain the T and E systems.

Answer 9

Provide a high speed always available connection via a dedicated logical circuit. Utilizes TDM (Time-division multiplexing) to allow a single T1 circuit to carry 24 channels.

Question 10

Give me the stats for T1 and E1

Answer 10

T1 = 24 channels @ 64 Kbps (1.544 Mbps)
E1 = 32 channels @ 64 Kbps (2.048 Mbps)

Question 11

Give me the stats for T3 and E3

Answer 11

T3 = 28 T1 circuits (672 channels) @ 44.736 Mbps
E3 = 16 E1 circuits (512 channels) @ 34.368 Mbps

Question 12

What is SONET?

Answer 12

Synchronous Optical Network. Uses fiber optical cabling to provide fault tolerant high-bandwidth WAN connections. Uses multiplexing to combine multiple T1 lines.

Question 13

What are the Data rates of OC-3, OC-12, OC-48, and OC-192?

Answer 13

OC-3 = 155.52 Mbps
OC-12 = 622.08 Mbps
OC-48 = 2.49 Gbps
OC-192 = 9.95 Gbps

Question 14

What is Metropolitan Ethernet?

Answer 14

Metro ethernet was introduced to provide a failsafe for cities and municipalities in case traditional Ethernet failed. It has now eveolved into CET (Carrier Ethernet Transport), through the use of the T-carrier system. CET establishes a virtual tunnel that uses a predetermined path.

Question 15

Explain satellite transmissions

Answer 15

Over 800 satellites are in geosynchronous orbit, providing non-terrestrial data streams. They are susceptible to cloud obstruction and rain fade. Latency is also an issue, running about 250 ms.

Question 16

Explain copper transmissions

Answer 16

Fundamental, legacy cabling that uses electrical signals to send transmissions.

Question 17

Explain fiber transmissions

Answer 17

A transmission medium that uses light (either LED or the more expensive laser) to transmit data at very high speeds. Is currently challenging copper cabling in many aspects.

Question 18

Explain wireless transmissions

Answer 18

The best example of a wireless WAN is a cellular network.

Question 19

What is MPLS?

Answer 19

Multiprotocol Label Switching. A connection-orientated method used to route data between nodes on a network over the most efficient route. It allows layer 3 to operate on layer 2. It allows packet-switching over circuit-switching.

Question 20

What is Frame Relay?

Answer 20

A group of layer 2 protocols were defined as a fast packet-switched network if ISDN connections. A PVC is established by routers and the frames are tagged with DLCI (Data-link connection identifier).

Question 21

What is ATM?

Answer 21

Asynchronous Transfer Mode. Transmits 53-byte cells (48 for data, 5 for header) to provide predictable, efficient networking.

Question 22

What is PPP?

Answer 22

Point-to-point protocol. Directly connects to endpoints on WAN. PPP uses headers and trailers to encapsulate packets with an additional 8 to 10 bytes. Supports authentication via protocols such as EAP or MS-CHAPv2.

Question 23

What is DMVPN?

Answer 23

Dynamic Multipoint VPN. Allows VPN tunnels to be created on demand, reducing the need for static site-to-site tunnels.

Question 24

What is the Demarcation Point?

Answer 24

Where the provider’s responsibilities end and the customer’s begin. (Phone pedestal, for example). Demarks will be a NID (Network Interface Device) or NIU (Network Interface Unit) placed directly outside or inside the building. Good place to start troubleshooting issues.

Question 25

What is Smart Jack?

Answer 25

A demarc device capable of monitoring the connections for data errors and reporting them to the provider. Can also be checked by a technician by reading the status lights.

Question 26

What is CSU?

Answer 26

Channel Service Unit. is usually a standalone device placed between the NID and first internal router. It servers as a digital signal termination point and uses error connection and line monitoring to ensure data integrity.

Question 27

What is DSU?

Answer 27

Data Service Unit. Built in with the CSU, converts the incoming frames from the T-carrier into Ethernet for the network. This process is reversed for transmissions.