4 ms·

For something like live video conferencing, it's true the packet loss is worse for audio then video. I was responding to the previous comment about how his stre

For something like live video conferencing, it's true the packet loss is worse for audio then video. I was responding to the previous comment about how his streaming experience over TCP was nearly instant. In the TCP case, of course you don't need to worry about loss.

jacquesm 9y ago
> In the TCP case, of course you don't need to worry about loss. You do, because TCP packets get lost at roughly the same rate as UDP packets do (though, there are some caveats here: on some congested links UDP packets tend to be dropped earlier). The only major difference is that TCP will cause the packet to be - eventually - resent. The price of this complexity is added latency due to the requirement to buffer for a longer time than it could conceivably take to re-transmit packets so you can continue to stream. If you ever exhaust that time a TCP based system will grind to a halt. In live video / real time conferencing such latency is really annoying and if it gets too long can be killing.
- kwindla 9y ago
  Elaborating on the "on some congested links UDP packets tend to be dropped earlier" ... In our testing of lots of internet connections in the US, we've found that many of the "free" modems/wifi-routers that cable and phone companies supply really, really discriminate against UDP. It's not completely clear whether this is intentional, at least in part, or whether it's just buggy behavior. There are several models of routers that you can reliable cause to just stop delivering UDP for a while, if you send enough UDP through them. This happens on their little internal Ethernet switches as well as over WiFi, so it's a firmware thing. Some of these routers will perk up and behave perfectly well right away, if you access one of the well-known DSL speed test sites, while flooding them with UDP packets. :-)

jacquesm 9y ago

> In the TCP case, of course you don't need to worry about loss. You do, because TCP packets get lost at roughly the same rate as UDP packets do (though, there are some caveats here: on some congested links UDP packets tend to be dropped earlier). The only major difference is that TCP will cause the packet to be - eventually - resent. The price of this complexity is added latency due to the requirement to buffer for a longer time than it could conceivably take to re-transmit packets so you can continue to stream. If you ever exhaust that time a TCP based system will grind to a halt. In live video / real time conferencing such latency is really annoying and if it gets too long can be killing.

kwindla 9y ago
Elaborating on the "on some congested links UDP packets tend to be dropped earlier" ... In our testing of lots of internet connections in the US, we've found that many of the "free" modems/wifi-routers that cable and phone companies supply really, really discriminate against UDP. It's not completely clear whether this is intentional, at least in part, or whether it's just buggy behavior. There are several models of routers that you can reliable cause to just stop delivering UDP for a while, if you send enough UDP through them. This happens on their little internal Ethernet switches as well as over WiFi, so it's a firmware thing. Some of these routers will perk up and behave perfectly well right away, if you access one of the well-known DSL speed test sites, while flooding them with UDP packets. :-)