I have a 2811 router connected via one of it's FastEthernet ports to a managed Cisco router which provides Internet access for us.
I would like to use QOS to give traffic to certain key websites priority over other traffic. I am familiar with QOS over serial connections, and those work great. But yesterday a group of our students all launched BitTorrent and World of Warcraft, and completely saturated our 3Mb/sec of Internet bandwidth the entire day. I would have expected our important traffic to be given more bandwidth and less likely to be dropped, but even at it's worst, the queueing did not seem to work.
Can anyone help?
set dscp af21
bandwidth remaining percent 75
set dscp default
bandwidth remaining percent 25
class-map match-any class_toMerit
match access-group name ACL_dest_merit
service-policy output pmap_Merit_Out
During the height of the bandwidth problems this is what a "show queue" displayed; which is not at all what I would expect from a totally saturated link:
#show queue fastethernet0/0
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
The most overlooked issue with managing Internet bandwidth is that the amount of outgoing traffic has no direct relation to the amount of incoming traffic. To state it simply: One mouseclick (=packet) will suffice to initiate a multi-megabyte download that will completely saturate the downstream link with the Internet for a long time. This seems to be exactly what is happening here as well.
It is not useful to police the outgoing (=upstream) traffic while your problem is with the downstream. You could rate-limit incoming traffic but that will not help you much; the traffic has already traversed the WAN-link (i.e. used bandwidth) and will be retransmitted by the sender when there is no acknowledgement. TCTIP is great in that! ;-)
When you look carefully at where the problem originates, the only place where policing the traffic would be useful is at the ISP-end of your Internet connection. Most ISP's are reluctant of this.
Thank you so much for your extremely fast and detailed reply! That is exactly what I was missing. I was focused on the speed differential (100 Mb/sec FastEthernet vs only 3 Mbit/sec of Internet), and completely overlooked the fact you mentioned.
That makes a lot more sense... In any case that I have used QOS successfully, it has been on a point to point link that I had control over both sides. But that is quite different than this case.
the problem is that the FE doesn't see congestion so the service-policy is ineffective. You need a "nested class map" so that traffic is first shaped at the 3 mbs that you can send to the internet, under it you will have your qos config that I *think* should work.
Hi everyone, I would like to thank you in advance for any help you can provide a newcomer like myself!
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