Verilink 9000 Series (34-00271) Product Manual - Manual (Page 284)

262 C HAPTER 15: IP L AYER A PPLICATION
IP datagram Time-to-Live
In each datagram sent by an IP device contains a Time-to-Live field in the IP
header. When originally supposed to represent a time interval, this parameter is
used as a hop count instead of a duration because the practice of networking shows
that it is almost impossible to synchronize a time base in a network. For historical
reasons, the name has remained but its usage is different. The selections for this
field range from a decimal 0 to 255, 16.
Reassembly timer
When a fragmented datagram is received, the IP Layer reassembles it before
passing it to the destination upper layer. Since IP is defined as an unreliable
protocol, there is no guarantee for the reception of all fragments of the datagram.
If, after the configured value, all the fragments are not received, the reassembly
process is aborted and all received fragments are flushed. The selections for this
field range are in seconds and range from a decimal 0 to 255, 30.
Link layer
This parameter specifies the protocol layer used by IP for communication with the
outside world. For now, only ETHERNET is supported.
IP auxiliary links
In the future, this will contain a list of auxiliary links used by the IP Layer for
communication with the outside world. It is not defined.
IP routers list
The IP routers list provides a list of available routers to the IP Layer for
communication with other networks. If a datagram has to be sent to a remote IP
device, the NETID portion of its IP address is compared with the local NETID. If
different, the datagram must be sent to a router to take care of delivering the
datagram using an unknown path. If all the devices desired to access are located on
the same network, they do not need to be configured.