Lets talk about common QoS implementation

[azev]

For most home users, they enabled QoS in effort to improve their VoIP or whatever traffic that they choose to give priority over others. I do not know about consumer grade routers, but In cisco implementation of QoS, most advance queuing technique can only be applied outbound. In congested enterprise LAN environment I can see many benefit that QoS provide, but I don't really see any benefit of QoS from typical home user.
Most home user traffic is "download" from the internet and maybe some upload traffic.
Unless you are pegging your upload traffic QoS doesnt really take effect.

Imagine this scenario; a user with 3Mb/1Mb internet speed is torrent-ing at maximum download speed, but limit his upload to 512K. When making a voip call during the download the inbound voice quality will suffer because the download speed is maxed torrenting. Then the user decided to play game; and noticed that the lag time is very high.
Let say the user enabled QoS, it really wouldn't do anything at all to improve the inbound Voice Quality, or the game lag time because QoS probably never really take effect. The only way to improve both the game and voice call is to police the download traffic to maybe 2.5Mb

IMHO the best method of QoS for home user (internet traffic) is really to police their most bandwidth hungry apps to not use all the download pipe.

just my 2c, let me know what you guys think on this topic.

Thx

 

[drebo]

Unless you control the entire network end-to-end, the only benefit from QoS that anyone will receive (business user or home) is in prioritization. Using a weighted fair queue forwarding policy, as opposed to strict round robin, will send your higher priority packets before your "best-effort" packets. Serialization delay is one of the biggest contributors to latency in a congested network, and can cause terrible quality issues with VoIP.

 

[alpineranger]

Sounds like you are confusing outbound from the perspective of a router with outbound from the perspective of a network. Lets say you have a cisco (or whatever non consumer grade router) between your home network and your isp. You could just use QoS and traffic policing on all outbound interfaces, but this corresponds to both upload and download traffic from the perspective of your home network.

So in the scenario you mentioned, you could control this, particularly if you could do QoS with respect to individual traffic streams (I'm not a cisco expert, so I'm not sure if this can be done, although I'm 100% sure it can be done with respect to generically different types of traffic using traffic classification prior to qos). That said, it's much easier to do it on the pc, and most people's routers either won't be able to do this sort of advanced qos, or won't be able to take the performance hit.

For most home users, they enabled QoS in effort to improve their VoIP or whatever traffic that they choose to give priority over others. I do not know about consumer grade routers, but In cisco implementation of QoS, most advance queuing technique can only be applied outbound. In congested enterprise LAN environment I can see many benefit that QoS provide, but I don't really see any benefit of QoS from typical home user.
Most home user traffic is "download" from the internet and maybe some upload traffic.
Unless you are pegging your upload traffic QoS doesnt really take effect.

Imagine this scenario; a user with 3Mb/1Mb internet speed is torrent-ing at maximum download speed, but limit his upload to 512K. When making a voip call during the download the inbound voice quality will suffer because the download speed is maxed torrenting. Then the user decided to play game; and noticed that the lag time is very high.
Let say the user enabled QoS, it really wouldn't do anything at all to improve the inbound Voice Quality, or the game lag time because QoS probably never really take effect. The only way to improve both the game and voice call is to police the download traffic to maybe 2.5Mb

IMHO the best method of QoS for home user (internet traffic) is really to police their most bandwidth hungry apps to not use all the download pipe.

just my 2c, let me know what you guys think on this topic.

Thx

 

[imagoon]

Sounds like you are confusing outbound from the perspective of a router with outbound from the perspective of a network. Lets say you have a cisco (or whatever non consumer grade router) between your home network and your isp. You could just use QoS and traffic policing on all outbound interfaces, but this corresponds to both upload and download traffic from the perspective of your home network.

So in the scenario you mentioned, you could control this, particularly if you could do QoS with respect to individual traffic streams (I'm not a cisco expert, so I'm not sure if this can be done, although I'm 100% sure it can be done with respect to generically different types of traffic using traffic classification prior to qos). That said, it's much easier to do it on the pc, and most people's routers either won't be able to do this sort of advanced qos, or won't be able to take the performance hit.

You have no control over what is sent to your network from outside unless you control the other side. QoS controls outbound per device. Once you hit the internet, most if not all routers will not honor your QoS settings and as such just send you packets as they come in.

So yes you can wreck a VoIP call or MMO session easily if inbound (download) is at 99% while upload is at 5%. Even if the channel sizes are different.

QoS would need to be implemented on the ISP side for you to QoS and control the download side on your network. Once the packets are on your line, it is pointless to have your router reject them as they have already been sent down the line over the slower connection.

QoS is a 2 way street. Both sides need to use it for it to be effective both directions.

 

[jlazzaro]

Once the packets are on your line, it is pointless to have your router reject them as they have already been sent down the line over the slower connection.

For UDP sure, but if you're policing TCP traffic inbound this act alone would throttle the transfer to the configured rate. QoS is both directions...queuing/shaping is outbound only.

 

[imagoon]

For UDP sure, but if you're policing TCP traffic inbound this act alone would throttle the transfer to the configured rate. QoS is both directions...queuing/shaping is outbound only.

And in many apps eventually drop the connection due to excessive TCP IP retries. Also that TCP information has already hit your line. You might be able to delay the acks or something but even that is hit or miss depending on what method is used to send the data.

If your app negotiates 1 ack / 50 packets, your still going to have 50 packets bombing your slow connection. Rejecting or trying to throttle on the receive end is largely ineffective.

 

[azev]

I guess policing a certain tcp steam inbound will cause it to reduce it's transfer speed to the pre-configured rate, but in theory, if I have a T3 line, I would like each of my tcp stream to get the maximum bandwidth available if the line is open. Only when there's congestion that I want certain traffic to be prioritized compared to other traffic. Lets say you have a T3 line, and during regular business hours the line is maxed out with typical business traffic (web,mail,ftp,etc), you aslo want to maintain great VoIP quality during this congestion period. You configured your outbound internet router for CBWFQ and shaping to give priority for your VoIP traffic, but unless your ISP/next-hop router can do the same, there's little benefit to enable QoS on your outbound traffic. Unless of course, if you internet traffic is primarily upload, you will surely benefited from the QoS that you applied.

 

[imagoon]

I guess policing a certain tcp steam inbound will cause it to reduce it's transfer speed to the pre-configured rate, but in theory, if I have a T3 line, I would like each of my tcp stream to get the maximum bandwidth available if the line is open. Only when there's congestion that I want certain traffic to be prioritized compared to other traffic. Lets say you have a T3 line, and during regular business hours the line is maxed out with typical business traffic (web,mail,ftp,etc), you aslo want to maintain great VoIP quality during this congestion period. You configured your outbound internet router for CBWFQ and shaping to give priority for your VoIP traffic, but unless your ISP/next-hop router can do the same, there's little benefit to enable QoS on your outbound traffic. Unless of course, if you internet traffic is primarily upload, you will surely benefited from the QoS that you applied.

When you start hitting the T3 levels, most ISP's will custom configure a router for you. Another trick is to channelize the connection and run the sensitive traffic on the 'priority' side. As the VoIP traffic increases, it 'pushes' the bulk channel smaller. What is best varies a lot. I know when you look at ATT SIP trunking, they want a dedicated line for them. However your internet line can act as a back up at reduced performance.

 

[azev]

When you start hitting the T3 levels, most ISP's will custom configure a router for you. Another trick is to channelize the connection and run the sensitive traffic on the 'priority' side. As the VoIP traffic increases, it 'pushes' the bulk channel smaller. What is best varies a lot. I know when you look at ATT SIP trunking, they want a dedicated line for them. However your internet line can act as a back up at reduced performance.

Interesting, we have multiple internet circuit (ds3 and gig metro e) from 3 different provider and we have no custom configuration with them other than the typical bgp stuff.
Maybe we need to engage the ISP and have a discussion about QoS with them.

Anyway, our MPLS circuit on the other hands are QoS enabled with different traffic classifications, all we have to do is mark the traffic and trust that the ISP will perform the QoS on their network.

I am thinking more in the realm of small networks with not enough leverage with ISP. I saw many current SOHO router claiming that they can do QoS, and I was curious if this is really the case.