Code change:
Some diffs are due to me reflowing text to fit the line limits, so please ignore those. Once we have this and a limit on announce IDs, it seems likely that we'll be able to get rid of 'Role', but for now it can stay.
Thanks NAME . this looks like a good improvement. I have few clarification questions and bit of extra work for you to add some informative text, if my comment seems ok to you.
Unfortunately, that makes it much more difficult for the server to tell abusive clients from valid ones, as we discovered with the recent HTTP/2 rapid reset attacks. In the end we did develop heuristics, but they're imperfect and in the process we broke a bunch of applications in an effort to defend against DDoS attacks. In contrast, QUIC had a system like this and experienced no issues and we didn't need to develop any new heuristics.
Currently, there's no way to limit the number of simultaneous subscriptions. QUIC stream limits cannot effectively be used to limit the number of subscriptions, so I'd suggest MoQ have a limit. The simplest idea would be to have a limit specified as a parameter in the server's SETUP message. As a related question, even with limits, what happens if a client subscribes to a number of streams that it doesn't have the bandwidth to support? ie: 10 4k video streams and they're on a slow link? Possibly the subscriptions could fail with an error code indicating that the server didn't have enough bandwidth to request them and/or serve them to the client?
rofl I just came here to post the same issue. See: URL I think we follow QUIC and have a MAXSUBSCRIBES frame. The initial value can be set in the SETUP message. The subscribe is considered active until the publisher sends or (TODO). I think we're okay with the subscriber/publisher using arbitrary subscription IDs if there's a single control channel. It would be easier if we required incremental subscribe IDs and you couldn't reuse them though.
Also do we need ? That seems like a potential attack vector too, since it involves inserting into a potentially CDN-wide routing table.
A few months ago, I would have said we should go with the HTTP/2 style design of just having a limit on number of streams, but given the recent issues, I'd be inclined towards the QUIC style of specifying the max number. But I think that works better if we also have a subscription ID that's monotonically increasing for subscriptions, ie: Announces also likely need some limits, but I'm less clear on how that might work.
I propose a monotonically increasing in the message. You can't reuse Subscribe IDs. We add a message containing the maximum allowed ID and possibly a SETUP parameter to set the initial value. The corresponding messages use that ID instead of echoing the full track name. This removes ambiguity and overhead. We would still have Track ID for compressing the full track name (maybe renamed?). You could have multiple SUBSCRIBE reference the same Track ID but contain different Subscribe IDs. For example: Same for .
Adding a Subscribe ID used as you're describing SGTM and as you said remove any ambiguity about what subscription is being referenced. Unless we are absolutely never going to have multiple subscriptions, I believe we'll need a Subscribe ID.
This is related to
may be better to name it as transaction_id . since it is id tied to a given subscribe transaction ..
As a follow-up to adding a Subscribe ID, we'll add a SETUP field or param to indicate the initial value and a MAXSUBSCRIBEID frame to increase the limit, similar to QUIC flow control.
The consensus at the session today was to go with a QUIC style approach, so I wrote There was interest in a similar approach for announces, but announces don't yet have an ID, so that will have to wait.
Will assign to Mike English
This seems like a really complicated way to limit the subscribes. I understand how it mirror streams but that had pretty different constrains. Why don't we just have an subscribe error of "too many subscriptions"? Discussed open issues in the 7 August 2024 virtual, not recorded here. Remaining issue (just do a SUBSCRIBE_ERROR?) went to the list and chairs declared rough consensus, although at least 2 participants would prefer not to have this.

Related discussion:
text: Duplicate Track Alias: The endpoint attempted to use a Track Alias that was already in use. <ins> Too Many Subscribes: The session was closed because the subscriber used a Subscribe ID equal or larger than the current Maximum Subscribe ID. </ins> GOAWAY Timeout: The session was closed because the client took too long to close the session in response to a GOAWAY (message-goaway) message.  See session migration (session-migration).