Re: [mpls] Reference Augmented Forwarding - MPLS RAF

[Haoyu Song <[e-mail]>]

[TS3]: Yet for other applications (like delay budgeted ones), the delay budget is for each path (and for each segment or transit hop on that path). Signaling such delay budget on that path will make it a per path state.

As noted this is an unrealistic use case. Unless you illustrate how to synchronize time in WAN to   the 10s of ns precision I am not going to spend any time on such a use case.

Besides you are going to waist much more precious forwarding time to analyze such budget at selected LSR then if budget is not met blindly and randomly drop packet ? If packets come too late receiving application can drop it. Putting burden to do such filtering into the IP/MPLS network is a truly terrifying idea (to say it lightly :)).


I actually don’t think this is a terrifying idea. 😊 If a packet is set to miss its delay target, it makes no sense to continue forwarding it because that will waste network bandwidth and processing power for both routers and end hosts.
Also, there is no need for network-wide synchronization for this use case. Each node can use its local clock to count the budget that has been used and pass the remaining  budget to the next hop. Of course, this way the transmission delay can’t be counted but that is constant for a link so it can be discounted in advance.
If we design also for possible innovations in future, we can’t ignore such use cases.

Best regard,
Haoyu