What is Test Equipment?
A general name for equipment used to configure, diagnose, and troubleshoot networking and telecommunications systems. Test equipment is invaluable to busy network administrators for troubleshooting local area network (LAN) or wide area network (WAN) connections, to system integrators who install networks and communication services at customer premises, and to wiring and cabling installation service people. You can buy test equipment for dedicated, single-use testing purposes, but multifunction test equipment is more cost effective.
Test equipment comes in all shapes and sizes, from rack-mounted equipment for enterprise troubleshooting, to hand-held scanners and packet sniffers, to laptops that run special software and use special PCMCIA-attached probes. Here are some examples:
Copper cable testers: Typically hand-held devices that can test installed copper cabling for compliance with EIA/TIA standards for cabling system performance. These are usually multifunction devices that support both coaxial cabling and twisted-pair cabling. Two-way testers enable you to test a cable from both ends.
Fiber-optic cable testers: Usually a separate category from coax/twisted-pair cable testers. These devices might support testing of single-mode fiber-optic cabling, multimode fiber-optic cabling, or both, and provide detailed measurements in decibels for optical link budget (OLB) calculations to ensure that a fiber installation will support the intended equipment layout. A typical fiber tester consists of two modules: a light source for injecting signals into the system at 850 or 1300 nanometers (depending on the type of fiber) and a power meter to measure what comes out the other end. Some devices include both functions and can be used to test fiber that is still on the spool.
Token Ring testers: Test for shorts, opens, and grounds on shielded twisted-pair (STP) cabling in Token Ring installations.
LAN analyzers (sniffers): For troubleshooting problems with LAN protocols at all levels of the Open Systems Interconnection (OSI) reference model protocol stack, from lower-level protocols such as Data Link Control (DLC), IPX/SPX, NetBEUI, and TCP/IP to higher-level protocols such as File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), NetBIOS, Server Message Block (SMB), and Simple Mail Transfer Protocol (SMTP). These devices basically capture LAN traffic and allow you to analyze and filter packets that use specific protocols, that are transmitted and received from specific computers, that are portions of a specific communication session between two computers, and so on. Microsoft Network Monitor, which is included with Microsoft Systems Management Server (SMS), Microsoft Windows 2000, and Microsoft Windows NT, is a software-based sniffer that runs on any PC with a network card and can capture and analyze most forms of LAN traffic.
SCSI testers: Test Small Computer Systems Interface (SCSI) buses for shorts, opens, or improper termination. These are usually dedicated to a specific type of SCSI interface.
ISDN and T1 test equipment: Includes continuity testers, channel testers, and line-quality analyzers for testing Integrated Services Digital Network (ISDN) and T-carrier circuits. They can sample frames to check for jitter and lack of synchronization.
WAN analyzers: Test serial transmission protocols such as RS-232 and V.35, which are used to connect WAN devices such as routers and bridges to Channel Service Unit/Data Service Units (CSU/DSUs). They are typically used to troubleshoot frame relay, High-level Data Link Control (HDLC), Point-to-Point Protocol (PPP), Synchronous Data Link Control (SDLC), Serial Line Internet Protocol (SLIP), Systems Network Architecture (SNA), and X.25 connections. You can connect a WAN analyzer to a serial connection by using a Y-shaped connector called a data tap, which lets you monitor communication without interfering with the data being transmitted.
Use a cable tester on a new enhanced category 5 cabling installation before you install and configure your Fast Ethernet network equipment. Good-quality cable testers typically test all four pairs of wires in unshielded twisted-pair (UTP) cabling over frequencies of up to 100 MHz or higher, checking cable integrity for shorts and opens, measuring cable segment lengths using time domain reflectometry (TDR), and allowing measurement of attenuation, near-end crosstalk (NEXT), and PowerSum NEXT to an accuracy of 0.1 decibels or better.
Cable testers can trace cables through walls, ceilings, and floors by measuring the length of a cable and telling you whether the cable is terminated, has an open end, is connected to a port on a hub, and so on. You can plug two-way cable testers into a wall plate and test the patch panel to find out which cable connects to the wall plate.