Echelon IP-852 Channel - Manual (Page 32)

24 IP-852 Channel Parameters
packets. The resolution of the timer depends on the IP-852 device. The resolution for
SmartServer and i.LON devices is in multiples of 10 milliseconds. The default
aggregation time is 16 milliseconds.
Figure 3.2 Aggregation Settings
If the network is idle and a single L ON W ORKS packet arrives at the
IP-852 device, the aggregation timer starts and the first packet is sent across the IP
channel without delay. If the network remains idle, the timer resets. However, if
another L ON W ORKS packet arrives within the aggregation time period, the router waits
the designated time for subsequent packets to arrive (anticipating a burst) so it can
aggregate before sending them onto the IP channel.
MD5 Authentication
MD5 authentication is a channel-wide property that uses an authentication key to set
security on an IP-852 channel. The authentication key is used to calculate the MD5
digest. When authentication is enabled and the IP-852 device prepares to send an IP
packet, the IP-852 device uses the authentication key and the public MD5 algorithm to
compute a digest over each L
ON
W
ORKS
packet in the UDP payload.
For standard channels, the packet format is described in the ISO/IEC 14908-4 standard
for sending L ON W ORKS packets over IP. The computed digest is appended to the end of
the packet and the packet is sent over the network. Authentication digests are appended
to both L ON W ORKS data packets and the IP-852 Configuration Server control packets.
One or more IP-852 devices receive the packet and use their authentication key to
compute a digest over the same payload (not including the appended digest). The
receiving IP-852 device compares the digest it computed to the one that was sent in the