icnd1 ch4
Terms
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- def: synchronous circuits...
- impose time ordering at the data link\'s sending and receiving ends. All devices agree to try to run at the same speed.
- def: clocking...
- the 2 CSU/DSUs adjust their clock speed to match the clocking signals from the telco. they also supply clocking signals to the routers so the routers react, sending and receiving data at the correct rate.
- what is DCE?
- Data Communications equipment. The device that provides clocking, the CSU/DSU.
- what is DTE?
- Data Terminal Equipment. The device that receives clocking, the router.
- WAN speed: DS0...
- 64 kbps
- WAN speed: DS1 (T1)...
- 1.544 mbps (24 DS0s, plus 8 kbps overhead)
- WAN speed: DS3 (T3)...
- 44.736 mbps (28 DS1s, plus mgmnt overhead)
- WAN speed: E1...
- 2.048 mbps (32 DS0s)
- WAN speed: E3...
- 34.064 mbps (16 E1s, plus mgmnt overhead)
- WAN speed: J1 (Y1)...
- 2.048 mbps (32 DS0s, Japanese standard)
- 2 most popular protocols used on point-to-point links:
- HDLC (high-level data link control) and PPP (point-to-point protocol)
- What is \"PCM\" in link speeds offered by telcos?
- pulse code modulation. The original mechanism used for converting analog voice to digital signal.
- Def of WAN terms: synchronous...
- time ordering on a bit stream. A device tries to use the same speed as another on the end of a serial link. However, by examining transitions between voltage states on the link, the device can notice slight variations in the speed on each end and adjust accordingly.
- def of WAN terms: clock source...
- the device to which other devices on teh link adjust their speed when using synchronous links.
- def of WAN terms: CSU/DSU...
- channel service unit/data service unit. Used on digital links as an interface to the telephone co. in the US. Routers usually use short cables from a serial interface to a CSU/DSU, which is attached to the line from the telco with a similar setup at the other router on the other end of the link.
- def of WAN terms: Telco...
- telephone company.
- def. of WAN terms: four-wire circuit...
- a line from the telco with 4 wires, made of 2 twisted pair wires. Each pair is used to send in one direction, so a 4-wire circuit allows full duplex communication.
- def. of WAN terms: T1...
- A line from a telco that allows transmission of data at 1.544 mbps.
- def. of WAN terms: E1...
- Similar to T1, but used in Europe. It uses a rate of 2.048 mbps and 32 64kbps channels.
- Other terms for a point-to-point leased line:
- leased line, leased circuit, link, serial link, serial line, point-to-point link, circuit.
- Packet-switching services: describe...
- Add routers to the service with a single serial-link from each router to the service. Each router can send packets to all other routers.
- 2 types of packet-switching service:
- Frame Relay, and Asynchronous Transfer Mode (ATM).