Hello dear MANRS community, We, at IELO (AS29075), are working on the question of DSPC tags transparency as ISP. To give more context, we are a French neutral infrastructure network operator, Tier 2 over France and west-europe and our main focus regarding products like transit or our FTTO with DIA are to be as neutral and efficient using peering over western Europe, PNI and multiple tier1 transits. On our internal network, like a lot of others, we have classification over equipment using for exemple Cisco "Traffic class", seeing old IP Precedence matching to mark signaling protocols from the very old RFC 791 to ensure that for our core interface, signaling protocols are put inside the best queue of the 7 on them. We currently do not (in most of cases) move any of DSCP service fields on our network, however, we do know that on our equipment, by defaults, DSCP fields P.E. of clients traffic will be, by default on the equipements, be interpreted and moved automatically into queues, that we might want to avoid. For exemple any client pushing all DSCP traffic with high priority value would if not changed, be interpreted as important as internal protocols. We do have seen other network resetting DSCP fields to 0 and other QoS parameters of trafic they do transport. On our side, we hesitate on how to manage client trafic "abnormal" trafic. Let's not say it's not non-legitimate, but might be wrongly interpreted by default behavior of network equipment. We do mostly do think that a best practice for a network operator should be to change clients interfaces to restrict high priority queues while not resetting DSCP field. It's an easy way to ensure to this day that we would keep everyone equal, but changing it, is by our current point of view, is a non-neutral action. However, attacks using DSCP field to abuse queuing behavior and might disturb equipment since they don't care what trafic it is before moving the queues is a difficult questions. RFC 4594#section-6 tries to answer a bit of it but lacks content and real issue. So, after exposing that, what we do ask for your opinion on the subject is : Should ISP and IXP remove (for exemple, many variants exists here) DSCP CS6 and CS7 fields from client trafic to reserve them for real signaling protocols and internetworking ? Or should we adapt our equipment policy to explicitly change the queue of such traffic without modifying them, thus making keeping the information of it quite difficult. Or should do not change any of them to keep as transparent as we can even though we might have trafic abusing equipment mechanics appear over the time. Or maybe should we all implement it the other way around by never using high priority to be used unless we exactly know that the trafic is to be treated as is and so only make priorisation where we are perfectly sure of it. Or anything else? What do you all think and manage these fields on your backbone and how we should reacts over them ? What should be/is the best practice for being neutral to them without having abusive flows? I think this question is important as well over IXP, where I think it could be as well be something to watch, and where the answer to the best practice to apply might vary here. I know this question clearly is NOT an hot topic for anyone, and probably is, let's say... not in vogue at all for anyone. But while it went inside our minds as we saw it and talked about it in our own team we could not reach an informed consensus on what's best for both internet transparency while avoiding abuse nor find. Best regards -- Martin Passard AS29075.net ielo.net Peering Manager / Network engineer