EMBEDDED APPLICATIONS FCT
LZT 123 8019 R1A
16
2.10
Advanced Technical Details
This section lists a number of advanced technical points
for users who wish to understand more of the fine details
of the TCP/IP stack in the radio device. For most readers
this information will not be relevant.
2.10.1
Time-to-Live (TTL)
The radio device IP stack uses a Time-to-Live (TTL)
setting of 64. This figure is fixed as far as the application-
writer is concerned; there is no high-level method for
changing it. Many modern systems use a TTL of 128, but
apart from the most complex of routing arrangements, a
figure of 64 will be perfectly adequate.
2.10.2
DNS Name Caching Period
The TCP/IP stack of the radio device caches DNS name
to address mapping data for a period of approximately 120
seconds after a successful lookup. During this period
subsequent name lookups for the same host will be
serviced from the cache with no query being sent to the
servers.
A maximum of six resolved hosts can be held in the cache
at any one time. If the cache is full and a new lookup is
submitted, the new lookup will fail until such time as the
oldest entry in the cache is deleted due to expiry of its
timeout.
