On Mon, 14 May 2007, Alia Atlas wrote:
In general, I find the specification having features that I don't see
necessary. Reporting ifIndex is not necessary (and the index is not
very useful as is to a human) if ifName is reported. Addresses are
already known from the source address though somewhat less reliably so
those need not be reported for outgoing interface use, and could also
result in reporting IPv6 link-local addresses (or IPv4 private
addresses) which wouldn't necessarily be useful or desired.
The idea with reporting the ifIndex is to provide the easy ability
to correlate that to MIB data. It is a common look-up key and I
believe it to be useful.
Using simply the source address doesn't handle topologies with
parallel links between routers. In that case, knowing the exact
outgoing link for troubleshooting is useful. ...
(A potentially interesting note: at least one implementation has an
internal 'interface index' which is different from 'SNMP ifIndex'.
The intent should be clear in the spec.)
If ifName is reported, is there significant benefit in reporting
ifIndex as well?
It could be more easily used for correlation, but that's only useful
for the operators of the network who could know the ifIndexes on the
routers, not outsiders. On the other hand, those network operators
can very well map the ifName to ifIndex using SNMP or similar tools as
well.
I'm not strongly against being able to report ifIndex (but I'd rather
that it doesn't get reported by default, at least to everyone), but it
seems like a feature that's more likely to clutter the traceroute
output with little added value: ifName should already provide the same
benefits and is a more generic mechanism.
[[ I don't have further to say about ifName vs IP address/nexthop/iif
reporting, so I've deleted it below ]]
--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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