Configuration Recommendations - Teldat Regesta-PLC Manual

Teldat S.A.
Chapter 3 Configuration Recommendations
• Keepalive mechanism in the tunnels
The keepalive mechanism determines the time (T) the device takes to detect a drop in a tunnel. Its value is determ-
ined by the Keepalive Period Reachable, Keepalive Period Unreachable and Keepalive Stability Threshold para-
meters in the following way:
T = Keepalive Period Reachable + (Keepalive Period Unreachable * (Keepalive Stability Threshold - 1))
DMVPN – Global Tunnel Settings.
Fig. 85:
To determine what values you should select, keep the following in mind:
- Short T Values
Advantages :
(a) They allow for a drop in tunnel connectivity to be detected rapidly, thereby reducing the time the device re-
mains inaccessible.
Drawbacks:
(a) The traffic generated by this mechanism isn't application traffic. Therefore, the lower the frequency these
packets are sent at, the more traffic is generated. Thus, the communication performance is lower.
(b) In low speed channels, if a traffic peak is produced, there is a high possibility keepalive packets won't arrive in
time and trigger a tunnel drop.
(c) They increase the possibility of tunnels being dropped due to small instabilities.
- Long T Values
Advantages :
(a) They reduce the traffic this mechanism generates and, consequently, increase communication performance.
(b) Traffic peaks and small connection instabilities do not affect tunnel maintenance.
Drawbacks:
(a) The device remains inaccessible for a longer period, as it takes longer to detect a drop in the tunnel.
In view of the foregoing, we recommend that this mechanism is configured with the following values. This way, a
drop in a tunnel will be detected in (approximately) 60 seconds:
Keepalive Period Reachable = 10 seconds between each keepalive transmission.
Keepalive Period Unreachable = 30 seconds between keepalive transmission in an unreachable state.
Keepalive Stability Threshold = 3 polling packets in an unreachable state to consider that the tunnel is down.
Regesta-PLC

3 Configuration Recommendations

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