RE: [EXTERNAL] Re: Can a prefix be never routed on Internet but used only for source address in IP packets?

["Sriram, Kotikalapudi (Fed) via NANOG" <nanog () lists nanog org>]

> We see this for example in a generalized pattern like instrument -> DAQ system -> UDP firehose -> FPGAs -> compute, 
> which is a completely unidirectional application workflow.

Is the prefix used in source address of the traffic unadvertised/unrouted on the Internet?

Is there any kind of check to see if the far side (FPGAs, compute) is available/ready to receive the data? 

Any thought given to what if the next hop AS (say, upstream to the DAQ system) is doing source address validation using 
uRPF? 

Thanks, Dale.

Sriram


-----Original Message-----
From: Dale W. Carder <dwcarder () es net> 
Sent: Tuesday, August 19, 2025 1:24 PM
To: North American Network Operators Group <nanog () lists nanog org>
Cc: Sriram, Kotikalapudi (Fed) <kotikalapudi.sriram () nist gov>
Subject: [EXTERNAL] Re: Can a prefix be never routed on Internet but used only for source address in IP packets?

Thus spake Sriram, Kotikalapudi (Fed) via NANOG (nanog () lists nanog org) on Tue, Aug 19, 2025 at 04:34:18PM +0000:
> Question:  Can a prefix be never routed on the Internet but used only one-way for source address in IP packets? 
>
> That is. a user owns an IP prefix. They never advertise a route to it in BGP on the Internet. But they use the prefix 
> solely for source address in IP traffic from a source to a destination (sink).  In this set up, the destination 
> server obviously cannot/doesn't return any acknowledgements etc. to the source.  Anyone aware if there is any such 
> known application in use on the Internet - even if it is rare? Thanks.

We see this for example in a generalized pattern like instrument -> DAQ system -> UDP firehose -> FPGAs -> compute, 
which is a completely unidirectional application workflow.

Dale

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