This chapter is from the book
This chapter is from the book
This chapter is from the book
Physical Layer Wired-Interface Features
This section describes the wired-interface feature options that you will encounter when you begin to research and select your wireless equipment.
NOTE
No wireless equipment vendor offers all the listed features in any model of their wireless equipment—nor should they. Each wireless network is built to serve a specific set of end user needs. These end user needs dictate the best set of wired and wireless features for that particular network. Each feature listed in the following sections is offered on at least one brand and model of wireless equipment. It is important that, as you consider the available features, you keep your wireless network needs in mind. Your equipment research involves finding the best match between your network needs and the wireless equipment feature set offered on a particular model of wireless equipment.
Your physical layer wired-interface feature evaluation includes some or all of the following:
- Low-speed data ports
- Ethernet ports
- High-speed data ports
- Voice interfaces
Low-Speed Data Ports
Most wireless equipment contains at least one low-speed port, such as the following:
Low-speed serial data ports—On some equipment, a low-speed serial data port is used for initial system configuration. The serial port speed generally ranges between 4800 bits per second (bps) and 19.2 kilobits per second (kbps).
Low-speed user data ports—Early wireless modems were frequently designed to transport only low-speed serial data over the wireless link. Port speeds range from 4800 bps to 128 kbps.
Dialup telco interfaces—Dialup telco interfaces provide low-speed dial backup connectivity for times when a higher-speed primary link, such as a T1 or digital subscriber line (DSL) link, is unavailable.
Ethernet Ports
Ethernet interfaces allow network data to access the wireless network. Wireless equipment can include one or more of the following Ethernet interfaces:
10Base-T—This is the most common Ethernet interface.
100Base-TX—This interface is found on higher-speed wireless equipment.
Ethernet hubs or switches—This interface is found on some wireless APs.
High-Speed Data Ports
In addition to Ethernet interfaces, it is often desirable to use wireless bridges or routers to transport other high-speed non-Ethernet data streams. To transport these streams, wireless equipment can include the following interfaces:
Digital subscriber line (DSL) interfaces—DSL interfaces enable a wireless bridge or router to extend or share a DSL connection.
Cable interfaces—Cable interfaces enable wireless equipment to extend or share a cable Internet connection.
Asynchronous Transfer Mode (ATM) interfaces—ATM interfaces enable wireless equipment to connect to and from an ATM network.
T1/E1 interfaces—T1/E1 interfaces enable wireless equipment to extend a 1.544 megabit per second (Mbps) T1 line or a 2.048 Mbps E1 line from point A to point B, for example, between two private automatic branch exchanges (PABXs). Some models of wireless equipment provide T1/E1 connectivity only. Other wireless equipment models provide simultaneous wireless Ethernet and T1/E1 connectivity.
TIP
Telecommunications managers who want to provide both Ethernet and voice-PABX connectivity between buildings find wireless equipment that simultaneously provides both Ethernet and T1 connectivity to be especially useful.
T3/E3 interfaces—45-Mbps T3 interfaces enable full-duplex wireless equipment to provide T3 connectivity between two points.
Optical Carrier 3 (OC-3) interfaces—155-Mbps OC-3 interfaces enable full-duplex wireless equipment to provide OC-3 connectivity between two points. Wireless OC-3 equipment usually has the capability to carry several T1 or E1 circuits in addition to the OC-3 circuit.
Optical Carrier 12 (OC-12) interfaces—622-Mbps OC-12 interfaces allow full-duplex wireless equipment to provide OC-12 connectivity between two points.
TIP
Remember that, in general, there is an inverse relationship between wireless bandwidth and wireless distance; as bandwidth goes up, distance goes down. OC-12 wireless equipment typically operates only over distances up to approximately 1312 ft. (400 m).
Voice Interfaces
Voice interfaces enable wireless equipment to carry voice in addition to data. The following types of voice interfaces are possible:
Voice over Internet Protocol (VoIP) interfaces—VoIP interfaces allow IP telephones to connect directly to the wireless equipment and to make on-network voice calls. Making calls to the public switched telephone network (PSTN) requires the use of an external telephone gateway.
Talkback/orderwire interfaces—A talkback interface (sometimes called an order wire) provides a two-way voice circuit. Maintenance personnel normally use this circuit for end-to-end voice communication over the wireless link while servicing the wireless equipment.
Wired-Interface Security Features
Physical layer wired-interface security features limit user access to the system administration console via a serial port or an Ethernet port. Successful entry of a password is required before gaining access to system administration functions. Additionally, some equipment allows a management station IP address to be configured. Attempts to access the system administration console from other IP addresses are refused.