Zyxel VES-1624FT-55A [104/312] Downstream and upstream

Zyxel VES-1624FT-55A [104/312] Downstream and upstream
Chapter 16 xDSL Port Setup
VES-1624FT-55A User’s Guide
104
16.5 DSL Standards Overview
These are the DSL standards and rates that the IP DSLAM supports at the time of writing. The
actual transfer rates will vary depending on what the subscribers device supports, the line
conditions and the connection distance.
16.6 Downstream and Upstream
Downstream refers to traffic going out from the IP DSLAM to the subscriber’s DSL modem or
router. Upstream refers to traffic coming into the IP DSLAM from the subscribers DSL
modem or router.
16.7 Configured Versus Actual Rate
You configure the maximum rate of an individual DSL port by modifying its profile (see
Chapter 17 on page 117) or assigning the port to a different profile (see Section 16.9.1 on page
106). However, due to noise and other factors on the line, the actual rate may not reach the
maximum that you specify.
Even though you can specify arbitrary numbers using the Edit Profile screen, the actual rate is
always a multiple of 32 Kbps. If you enter a rate that is not a multiple of 32 Kbps, the actual
rate will be the next lower multiple of 32Kbps. For instance, if you specify 60 Kbps for a port,
the actual rate for that port will not exceed 32 Kbps, and if you specify 66 Kbps, the actual rate
will not be over 64Kbps.
Regardless of a profile’s configured upstream and downstream rates, the IP DSLAM
automatically limits the actual rates for each individual port to the maximum speeds supported
by the port’s DSL operational mode. For example, if you configure a profile with a maximum
downstream rate of 25000 Kbps, and apply it to a port set to use G.dmt, the IP DSLAM
automatically uses a maximum downstream rate of 8160 Kbps. This means that if you
configure a profile with very high rates, you can still use it with any port. See Table 18 on page
104 for a list of the maximum rates supported by the different xDSL standards.
16.8 Default Settings
The default profile always exists and all of the DSL ports use the default profile settings when
the IP DSLAM is shipped. The default profile's name is set to
DEFVAL_MAX.
See Chapter 54 on page 283 for the settings of the default profile and DSL port default
settings.
Table 18 DSL Standards Maximum Transfer Rates
STANDARD MAXIMUM DOWNSTREAM MAXIMUM UPSTREAM
8a/b/c/d 85 Mbps 18 Mbps
12a/b 85 Mbps 50 Mbps
17a 100 Mbps 50 Mbps
ADSL2+ 24 Mbps 1 Mbps

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