• In a client/server arrangement, network services are located on a dedicated server.

• The server is a central computer that is continuously available to respond to requests from clients for file, print, application, and other services.

• Most network operating systems adopt the form of a client/server relationship.

• Typically, desktop computers are the clients and one or more computers with additional processing power, memory, and specialized software function as servers.

•easy to create •no centralized equipment required •centralized administrator not required

•centralized security •centralized backups •enhanced network services

5.2.1 WAN physical layer

ISDN BRI is 2 Bearer channels plus a Data channel (2B+D).

The B channels use PPP (Point –to-Point Protocol).

The Service Provider usually provides the clock at the DCE connector end.

Use roll-over cables to connect a terminal to a console port.

The auxiliary port is a console port but you connect with a modem.

The console port is for initial router configuration.

Use roll-over cables to connect a terminal to a console port.

The auxiliary port is a console port but you connect with a modem.

The console port is for initial router configuration.

xDSL - Digital Subscriber Line Technology

• The key in xDSL technology is modulation, a process in which one signal modifies a properties of another.

• Hardware: DSL requires modems and splitters for end-users; carriers use DSLAMs (digital subscriber line access multiplexers)

• Differences between xDSL technologies: speed, operating distance, applications, ratio between up and downstream

• Different approaches: ATM-based ADSL, ISDN DSL.

• The important thing is what is running over xDSL...

xDSL - Digital Subscriber Line Technology

xDSL Digital Subscriber Line Technology

ADSL - Asymmetric Digital Subscriber Line •expected in general use in 1999 •twisted pair copper (single loop) •asymmetric: most commonly: 6Mbps (down), 640 Kbps (up)

•downlink: 1.5 Mbps-8 Mbps •uplink : 176 Kbps - 1 Mbps

•limited distance (18000 feet over 26-gauge copper)

RADSL - Rate-Adaptive Digital Subscriber Line •varying speeds depending upon line quality; asymmetric

•downlink: 1.5 Mbps-8 Mbps •uplink : 176 Kbps - 1 Mbps

•limited distance (18000 feet over 26-gauge copper)

xDSL Digital Subscriber Line Technology (cont.)

HDSL - High-speed Digital Subscriber Line •full-duplex, symmetric

•1.544 Mbps or 2.048 Mbps in each direction •two twisted pairs (for T1) and 3 pairs (for E1) •max distance 12,000 feet

VDSL - Very-high-bit-rate Digital Subscriber Line (known as BDSL)

•asymmetric •downlink: 12.96-51.84 Mbps •uplink : 1.6 - 2.3 Mbps

•max 4,500 - 1,000 feet •applications: High definition TV, multimedia

1. A network interface card (NIC) provides network communication capabilities to and from a PC. 

2. Use a crossover cable to connect between two similar devices, such as switches, routers, PCs, and hubs.

3. Use a straight-through cable to connect between different devices, such as connections between a switch and a router, a switch and a PC, or a hub and a router.

4. There are two major types of LANs, peer-to-peer and client/server. 5. WANs use serial data transmission. WAN connection types include

ISDN, DSL, and cable modems. 6. A router is usually the DTE and needs a serial cable to connect to a

DCE device like a CSU/DSU. 7. The ISDN BRI has two types of interfaces, S/T and U interfaces. To

interconnect the ISDN BRI port to the service-provider device, a UTP Category 5 straight-through cable with RJ-45 connectors, is used.

8. A phone cable and an RJ-11 connector are used to connect a router for DSL service.

9. Coaxial cable and a BNC connector are used to connect a router for cable service.

10. Rollover cable is used to connect a terminal and the console port of an internetworking device.