L-IP User Manual
95
LOYTEC
Version 6.1
LOYTEC electronics GmbH
Timing Parameter
Value
Channel Timeout
Average ping delay + Aggregation Timeout
Escrowing (Packet
Reorder Timer)
The smaller value of: 0.25*Channel Timeout or 64ms
Aggregation Timeout
(Packet Bunching)
Typically 16 ms
Channel Delay in
LonMaker
Average ping delay +10% + 2* Aggregation Timeout
Table 8: Advanced IP-852 timing parameters.
Please use a PC to determine the average ping delay between the different CEA-852 devices
in the network. If multiple devices are communicating with each other always use the largest
measured average ping delay for the input value for the calculations in Table 8.
Escrowing should be disabled in a LAN (0 ms). The Channel Delay in LonMaker should be
set to 2*Aggregation Timeout in a LAN if MD5 is disabled.
In LANs, Channel Timeout is only required if MD5 authentication is enabled. Set Channel
Timeout to 200 ms and Channel Delay to 20 ms.
7.5.1 Channel Timeout
The Channel Timeout is a property of the IP-852 channel. If a packet travels across this
IP-852 channel for longer than what is specified in Channel Timeout in ms, the packet is
discarded. The device always needs to synchronize with an SNTP timeserver when a
Channel Timeout is set other than 0 ms.
Channel Timeout is highly recommended if MD5 authentication is enabled in order to
prevent replay attacks. Set Channel Timeout to 200 ms and Channel Delay to 20 ms in a
LAN environment. Please refer to Section 6.2.12 on how to enable or disable the Channel
Timeout.
If an LNS based network management tool like LonMaker or NL220 is used on a network
that has channel timeout enabled, please install an NTP client program (e.g., achron4.exe)
on this PC that synchronizes the PC clock to the NTP time. Otherwise the PC clock and the
clock inside the CEA-852 device will drift apart and communication between the PC and
the device will terminate.
7.5.2 Channel Delay
Channel Delay is an LNS channel property that specifies the expected round-trip time of a
message and its response. This value is used by LNS to adjust the protocol timers in the
CEA-709 nodes. Please consult the documentation for your network management tool about
the Channel Delay details.
7.5.3 Escrowing Timer (Packet Reorder Timer)
The Escrowing Timer or Packet Reorder Timer is an IP-852 channel property that specifies
the amount of time the device will wait for an out-of-sequence IP packet to arrive. This
parameter is important in WANs like the Internet where packets pass many routers that can
change the order in which packets arrive at the destination node. The default value is 64 ms.
Do not use the Escrowing Timer in LANs since the packet order is always guaranteed in a
LAN. This will add unnecessary delays, which negatively impacts the performance of your
CEA-852 devices if a packet is lost or destroyed.
If enabled or disabled, out-of-sequence packets are never sent to the CEA-709 channel.
Please refer to Section 5.7 and 6.2.10 on how to enable or disable escrowing.