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Comment by jeroenhd | Hacker News Reader

Practically: however many your computer and uplink can serve. OBS needs to be tested, but this browser to browser test may give some indication: https://tensorworks.com.au/blog/webrtc-stream-limits-investi....

If you've got 100 viewers and can manage to saturate a gigabit uplink (which can be difficult because of routing and other upstream crap) you should be able to send about 9mbps video + overhead, which is pretty close to Twitch's bandwidth cap.

Because consumer ISPs generally don't have great routes between them and sustained gigabit uploads probably don't always work reliably because of overbooking with consumer lines, you'll probably be better off setting up an SFU on a cheap (temporary) cloud server somewhere.

Theoretically: media streams are identified by a 32 bit number, so about 4 billion clients.

Data streams are limited to 65535 endpoints (a signed 16 bit number with a reserved 0).

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Not sure why you think that? Maybe on cable modems, because DOCSIS is highly asymmetrical, but on FTTH GPON et al (pretty much the only technology which supports gigabit upload; docsis gigabit upload is extremely rare), there is no reason it couldn't saturate upstream at 1gigabit+. If anything, consumer ISPs are usually way more contended on the downlink side than the upstream side.

> Maybe on cable modems

Maybe I'm wrong but I'm pretty sure cable modems are still wha the vast majority of consumer households have.

Yes but the parent is referring to gigabit upstream connections. Very few gigabit upstream services are over DOCSIS. I don't know of a single provider that offers gigabit upstream on docsis. In the UK Virgin Media offer 100mbit/sec up on their top tier (1gigabit down). I think the fastest Comcast goes in the US is 200mbit/sec up over docsis and that's only in certain areas.

GPON is typically shared bandwidth; 2.5Gbps for n customers (that could be an entire building, or the 4 houses adjacent to a box in the backyard, etc.)

More advanced fiber networks split bandwidth based on frequency ("color") instead of giving each ONT a time slot based on the current network capacity. But basically, if you're uploading at 1Gbps, that is fine until 1.5 more neighbors decide to do the same thing. It's rare. When I worked at Google Fiber we kept an eye on PON utilization and there was never a case where a customer couldn't get the requested bandwidth. We even had customers that maxed out 1Gbps/1Gbps 24/7 in an attempt to get banned or something, but of course we wouldn't ban you for that. We did worry about PON capacity and had some tech ready to go in case we ever needed to switch to truly dedicated per-customer gigabit connections.

At another ISP I worked at, our marketing material described the 1Gbps GPON-based link as "dedicated", but many customers noticed it was shared. It would slow down during peak business hours, and then get fast when other people in the building went home from work. We removed the term "dedicated" from our marketing. A political battle that I paid dearly for, but hey, they still exist and didn't get sued into oblivion by the FTC, so that's nice. (We also sold frequency-multiplexed 10Gbps circuits that really were dedicated... I suppose until our uplink to our ISP was saturated. I think we had 100Gbps transit and that never happened. But yeah, there is no such thing as dedicated unless you are physically plugged into the network that you want to reach. The Internet tries its best.)

I know that GPON is shared; but as you say it's rarely the 'weak link'. Regardless, even if it was, it's much more likely that the downstream would be saturated on the gpon level vs the upstream - consumer ISPs are much more downstream heavy than upstream heavy, so I have no idea what the parent post means when he says that its hard to saturated gigabit uplink on consumer connections. It's the opposite if anything.

It’s not about bandwidth inside the AS, but about fiber peering from ISP datacenters “to the Internet”. I don’t have anyone’s internal informations but that must cost 10-100x more than $35/Gbps/month. Residential internet is gym membership model, a best effort offering. Resources are always heavily over-committed based on typical use cases of groups of average users.

“consumer ISPs generally don't have great routes between them” is the way more important part.

An eyeball network will generally have considerably more, and considerably higher bandwidth, peering relationships with content provider networks than with other eyeball networks.

At AVStack we experimented quite a bit with P2P multiparty video calls, it’s certainly possible but as you scale up the number of participants there’s huge variance in quality depending on the combination of ISPs used by the participants, the time of day, network conditions etc.

What do you mean by Twitch's bandwidth cap? Obviously Twitch supports more than 100 viewers, so is this an upstream cap from the streamer or a downstream per user cap or something different all together.

A glace over Twitch's broadcasting guidelines was not enlightening, but I'm clueless in these matters.

He means the cap on the bitrate of the video that twitch will ingest. Twitch will then send this video to any number of viewers, as you say.

If you send more than about 6.75mbps of video to Twitch, you'll start getting errors. With the variable size of encoded streams you need to play with the cap a little to get a problem-free experience.

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