jfmezei
Premium
join:2007-01-03
Beaconsfield, QC
 ·ELECTRONICBOX
| QoS question (sort of urgent)
Question:
Is it technically correct to state that many routers today support QoS and can prioritise a user defined traffic ?
Also, in such a scenario, does the router set the "urgent" bit in the packet header ? Or is there no tagging of packets that are considered "priority" by the user ? |
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planiwa
join:2009-02-19
Toronto M5S
| QoS in consumer-appliance routers is not the same as (original) internet-routing QoS.
Consumer-router QoS consists strictly of classifying traffic, and allocating the upstream bandwidth between the class-queues.
For each class there are two parameters:
MIN -- guranteed BW for this class
MAX -- maximum BW that this class may use, even if there are no queues of higher priority.
The idea behind all this is that by slowing Upstream traffic we can slow Downstream traffic, and removing upstream congestion will let higher priority traffic flow both ways.
While some routers make it possible to class-restrict downstream traffic as well, it is generally considered too late, since the BW is used up by the time the packed arrives, and discarding it will result in its being resent and using even more BW (&congestion).
What happens when the sum of the MINs exceeds 100% is undefined.
There is an implicit (but rarely stated) assumptions that the classes have an intrinsic priority sequence. Sometimes this is assumed to be implicit in their name (A,B,C ...). Sometimes it is assumed to be implied by their MIN value.
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»[RFC] Connection / Speed Problems Checklist |
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An_Onymous
@teksavvy.com
| reply to jfmezei
The user to define on a per physical port and/or /TCP/UDP port basis. They can reorder the packets in the Egress queue based on the priority.
The QoS only let the user set the Egress traffic as it has no control what so ever on the Ingress path. |
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Angelo_
The Network Guy
Premium
join:2002-06-18 | reply to jfmezei
it's user descided... without the user setting what they consider is class 1 -6 for instance qos will never work... |
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Martian3
join:2004-10-17
Lindsay, ON
·TekSavvy Solutions..
| reply to jfmezei
said by jfmezei  :Question: Is it technically correct to state that many routers today support QoS and can prioritise a user defined traffic ? It's technically correct, although I'd call it a partial answer due to the reasons mentioned above. QoS as implemented by consumer-grade networking hardware as not the same as QoS as implemented by commercial-grade stuff. So far as I know consumer-level QoS does not modify the outgoing packets in any way, but simply classifies it and queues it accordingly.
There's no way to implement downstream traffic shaping effectively at the router, if that's what you're asking; by the time it gets that far, it's already passed the major bottleneck, which is generally speaking the broadband link. If, for example, I wanted to throttle bittorrent traffic myself to ensure adequate bandwidth for a VoIP line, I'd have to do it in the bittorrent software or not at all. Since incoming traffic is in almost all cases solicited, this isn't usually a major concern. |
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