3com S7906E Manuel De Montage
2-2
EPON System Parameter Configuration
Configuring the maximum ONU-OLT RTT
During ONU registration, an OLT obtains the Round Trip Time (RTT) value of an ONU through the
exchange of discovery GATE messages and REGISTER_REQ messages between the OLT and the
ONU. By configuring a maximum RTT at the OLT side, you can set the coverage range of the EPON
system. An ONU whose RTT is greater than the RTT configured on the OLT cannot be registered.
exchange of discovery GATE messages and REGISTER_REQ messages between the OLT and the
ONU. By configuring a maximum RTT at the OLT side, you can set the coverage range of the EPON
system. An ONU whose RTT is greater than the RTT configured on the OLT cannot be registered.
Setting a short RTT prevents ONUs too far away from the OLT from being registered with the EPON
system (a far-away ONU suffers high optical power attenuation). Setting a long RTT can expand the
coverage range of the EPON system, allowing as many ONUs as possible to be registered successfully.
system (a far-away ONU suffers high optical power attenuation). Setting a long RTT can expand the
coverage range of the EPON system, allowing as many ONUs as possible to be registered successfully.
The process of RTT measurement is as follows:
1) The OLT sends an ONU a discovery GATE message containing the OLT local time T
0
, namely, the
time stamp in the discovery GATE message is T
0.
2) Upon receiving the discovery GATE message, the ONU modifies its local time to be the time stamp
T
0
in the message and sends a REGISTER_REQ message to the OLT at T
1
after a delay
(the time
stamp of the REGISTER_REQ message is T
1
).
3) The OLT receives the REGISTER_REQ message at T
2
.
4) The OLT calculates the ONU RTT by using the formula: RTT=(T
2
-T
0
)-(T
1
-T
0
)=T
2
-T
1
.
5) If the OLT becomes idle at T
3
and remains idle for a period of ∆T, the timeslot assigned to the ONU
is { T3-RTT, ∆T }. That is, the ONU will start sending data at T3-RTT and send data for a period of
∆T.
∆T.
Follow these steps to configure EPON system parameters:
To do…
Use the command…
Remarks
Enter system view
system-view
—
Enter OLT port view
interface
olt interface-number
—
Configure the Maximum
ONU-OLT RTT
ONU-OLT RTT
max-rtt value
Optional
13524 TQ by default
13524 TQ by default
Exit to system view
quit
—
Enter FTTH view
ftth
—
Configure OUI and extended
OAM version number list
OAM version number list
epon-parameter ouilist
{ oui
oui-value oam-version
version-value
version-value
} &<1-9> slot
slot-number
Required
By default, the OUI and
extended OAM version number
must be configured as 111111
and 1 respectively.
By default, the OUI and
extended OAM version number
must be configured as 111111
and 1 respectively.
Configure the key update time
and encryption reply timeout
time of the encryption
and encryption reply timeout
time of the encryption
encryption timer
{ update
update-time |
no-reply-timeout timeout
no-reply-timeout timeout
}*
slot slot-number
Optional
By default, the key update time
is 10 seconds and the
encryption reply timeout time is
3000 milliseconds.
By default, the key update time
is 10 seconds and the
encryption reply timeout time is
3000 milliseconds.