varaillon <> wrote on Tuesday, August 21, 2007 9:20 AM: > I have few questions about queuing on Cisco. > > 7200----HDLC/ISIS/TDP----26xx > > I have set-up QoS between the two Cisco routers mainly use to carry > voice traffic, as follow: > > Queue1: Voice Bearer - LLQ - priority bandwidth 55% > Queue2: Voice Signaling - CBWFQ - bandwidth 10% > Queue3: Any IP traffic - CBWFQ WRED - bandwidth 10% > Queue4: default > > * If my LLQ queue is full, can it borrow bandwidth from any other non > full queues including the default one?
No, "priority" implicitly configures a policer, and excess packets are dropped. > * If any of my CBWFQ queues is full, can it borrow bandwidth from any > other non full queues including the default one? Yes. > If I use the command "max-reserved-bandwidth 90" on the serial > outgoing interface of both routers, and if I have the following > queues: > > Queue1: Voice Bearer - LLQ - priority bandwidth 70% > Queue2: Voice Signaling - CBWFQ - bandwidth 10% > Queue3: Any IP traffic - CBWFQ WRED - bandwidth 10% > Queue4: default Usually you don't want to provision more than 50% of your BW for LLQ. Experience has shown that this can introduce some delay.. What would you put into the default class? See also comment below. > What would happen in case of congestion: > > * Since I know that I have very little IP traffic, Queue 3, > guaranties that the TDP session won't go down, right? well, since you enabled WRED, we could also drop TDP packets.. > * Since the default queue has the remaining 10% of the bandwidth, > HDLC and ISIS won't go down, right? well, first of all you also want to reserve BW there, i.e. add "bandwidth percent 10" as well. Then check out http://www.cisco.com/warp/public/105/rtgupdates.html to see how your platform treats those packets. > * So, in this case and despite Cisco advices on that matter, is it > safe to use the "max-reserved-bandwidth 90" command? I would think so. > * Do I risk to lose the serial link due to a lack of bandwidth? > > * Do I risk anything else? No, looks good with the above changes.. oli _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
