Mitel MiVOICE BUSINESS, Инструкция по инженерии

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Engineering Guidelines
290
CABLES AND CONNECTIONS
Although often hidden, the cable plant provides the connection between the end user and the
data service (the IP phone and 3300 ICP). Because data is sent at high speed, there are
requirements that need to be met in order to get the best performance.
Once sent, voice packets cannot be recovered, and so it is important to ensure that the cable
plant is capable of handling the data without loss, or at worst a factor of 10 better than the
guidelines for “green” operation as shown in the section “Network Measurement Criteria” on
page 210. This must be verified before installation. A lossy network might not show itself with
PCs attached because PCs resend information if it is lost. The effect for the PC user is simply
a slow file transfer. The effect on the IP phone user is interrupted conversation.
Use the guidelines in the following sections to ensure a good network installation.
CABLE TYPES
Use a minimum standard of CAT 5 cable between devices. For added performance, use CAT 5e
or better between patch panels and between switch devices. Total cable lengths should not
exceed the Ethernet requirements as highlighted in specification ANSI/EIA/TIA-568-B 2001,
section 4.
ANSI/EIA/TIA-568-B 2001 also highlights good wiring practices, such as
• Grounding requirements
• Cable runs and mixing of cable types
• Cable bend radii
Cables are available in a number of data types. Those recommended for this application are
• CAT 5
• CAT 5e
• CAT 6.
Connectors should also conform to the same requirements. If the cable used is CAT 6, but the
connectors are CAT 5, then performance will not exceed CAT 5. If CAT 3 connectors are used,
the cable run is not guaranteed to work at CAT 5 rate.
Consider other possible uses for the cables and future expansion requirements. It is easier to
specify a slightly higher-grade cable at initial installation than it is to retrofit later. Structured
wiring schemes are always preferred as they can be connected in star and ring configurations
with little change within the building.
Note: Examples of acceptable wiring, equipment installation and grounding practices
can be found in Ethernet Cabling Guidelines in the 3300 ICP Hardware Technical
Reference Manual .
Note: Refer to “CAT 3 Wiring Practices” on page 297 for guidelines and restrictions
when CAT 3 is encountered in an existing installation.