12-09-2012, 10:52 PM
T4 Timeout No RNG-REQ Grant MAP Received by Cable Modem in 35 sec – Typically a Downstream Problem
T4 timeouts can usually be identified with downstream impairments causing the cable modem to miss receiving the RNG-REQ grant MAP transmitted to it
If T4 errors are impacting many modems off of a common leg, trouble shoot that leg
If T4 errors are just associated with one modem, look for low MER/level at that modem
T4 timeouts can also be associated with a CMTS that has extremely high utilization i.e. >95% depending on the vendor and firmware version
Rule of thumb for CMTS utilization is 80% to allow for peak usage periods
It is highly unlikely that T4 timeouts are associated with any upstream impairments
T4 timeouts can usually be identified with downstream impairments causing the cable modem to miss receiving the RNG-REQ grant MAP transmitted to it
If T4 errors are impacting many modems off of a common leg, trouble shoot that leg
If T4 errors are just associated with one modem, look for low MER/level at that modem
T4 timeouts can also be associated with a CMTS that has extremely high utilization i.e. >95% depending on the vendor and firmware version
Rule of thumb for CMTS utilization is 80% to allow for peak usage periods
It is highly unlikely that T4 timeouts are associated with any upstream impairments
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