My off-the-cuff answer is that the udpEndpointInstance
exists in order to distinguish between multiple UDP Endpoints
that are otherwise identical, so its specific value doesn't
matter at all (otherwise than that it's unique, which is
required by the fact that it's in the INDEX). One imagined
implementation is to use the [low-order bits of] the address
of the kernel data structure (e.g., see BSD's "netstat -A"
output).
This could work and is quite efficient however what happens if the structure is
freed. It could be part of a cache (in solaris it is) and can be reused possibly
for the same ip/port combination. How would one differentiate that it's a new
instance
and not the old one. Actually this is a generic issue even when the index is zero. How does
a consumer know that it's a new instance and not an old one ? Also it seems strange that the
index numbers would be so high and out of sequence.
Hello,
Just wanted to add that in our TCP/IP implementation, the instance identifies
an endpoint to a
network management application. We created a proprietary SNMP table
that augments udpEndpointEntry, so we could provide counter statistics
(datagrams, octets) for the endpoints. So if a management app is
polling the UDP endpoint information, it uses the instance to recognize
updated counters for an endpoint. We increment the instance value
for each new endpoint.
How do you assign an instance id and what do you do about reuse and roll over.
I think the working group should clearly define the characteristics of the
instance id.
Provided instance ID's can be reused I suggest we use an incremental instance id.
When an endpoint is created it's assigned the highest instance id or zero if its the first instance.
Instance ID's can roll over to find the next unused ID. This lowers the
frequency of ID being reused.
Rao.
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