NTAC Peering Working Group

[Michael H Lambert <>]

Paul,

On 30 May 2013, at 11:53, Paul Schopis wrote:

> 4. Substrate comment by Michael - Agreed, it is not very interesting if all 
> it is used for is IP transport. But not sure I get the comment about 
> test/diagnostic packets, again I think depends on what it is your trying to 
> diagnose. Could you elaborate?

My thoughts were sort of meandering this this direction:

Let's say I am sitting on a.hawaii.edu and running an application between 
that host and b.maine.edu (that should make for a long path with lots of 
devices).  On a traditional IP network, if I do a traceroute I'll feel fairly 
confident that the traceroute packets are following the same path as my data 
packets.  However, if I'm running my SDN-aware application on an SDN-enabled 
network, I probably won't have that same confidence.  The application can 
provide hints, requests or demands to the network; these can affect the 
path(s) taken through the network (short-circuiting layer-3 completely, 
perhaps).  Unless sdntraceroute is provided with the same parameters (and 
maybe not even then if the volume of data affects the path), there is no 
reason to assume any congruence between the application and traceroute paths, 
except, perhaps, at the first and last hops.

An issue now during an initial deployment of an IP network on top of SDN?  
Probably not.  A problem a few years from now when we are actually leveraging 
SDN?  Quite likely.

Michael