Traceroute path consistency
Hi all, I have a suggestion regarding the udp traceroute feature: allowing the user to specify the source port. The motivation for this suggestion is to keep consistent paths between two traceroutes towards the same destination. I understand that the source port is used to discriminate concurrent traceroutes, so perhaps allocating a range for user-defined source ports would do the trick. There is of course the issue of two users selecting the same source port for the same destination but this is very unlikely. Do you think this is feasible ? David
On 08/15/2012 07:39 PM, David Lebrun wrote:
There is of course the issue of two users selecting the same source port for the same destination but this is very unlikely.
Correction: the issue is two users selecting the same source port for *any* destination. This becomes a bit more likely, so perhaps delaying the measurement until the port is available would fix the problem.
On 8/15/12 12:39 , David Lebrun wrote:
I have a suggestion regarding the udp traceroute feature: allowing the user to specify the source port.
The motivation for this suggestion is to keep consistent paths between two traceroutes towards the same destination. I understand that the source port is used to discriminate concurrent traceroutes, so perhaps allocating a range for user-defined source ports would do the trick.
The paris-traceroute mode, which is default for firmware above 4400 keeps the source port consistent as long as a UDM is running on a probe. It does vary the destination port to trigger different routes, but the variation is included in the output (paris_id) Unfortunately, for IPv4 the source port is needed by the traceroute implementation, so it cannot be made user settable.
Unfortunately, for IPv4 the source port is needed by the traceroute implementation, so it cannot be made user settable.
could you go into a bit of detail on 'needed'? randy
On 8/15/12 15:12 , Randy Bush wrote:
Unfortunately, for IPv4 the source port is needed by the traceroute implementation, so it cannot be made user settable. could you go into a bit of detail on 'needed'?
To keep things simple, the source port encodes the index in a table of measurements. In theory, a user-settable source port together with the destination address could be used as input to a hash table or a red-black tree.
participants (3)
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David Lebrun -
Philip Homburg -
Randy Bush