[c-nsp] QoS - questions

[varaillon]

Hi,


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?

* If any of my CBWFQ queues is full, can it borrow bandwidth from any other
non full queues including the default one?


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

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?

* Since the default queue has the remaining 10% of the bandwidth, HDLC and
ISIS won't go down, right?

* So, in this case and despite Cisco advices on that matter, is it safe to
use the "max-reserved-bandwidth 90" command?

* Do I risk to lose the serial link due to a lack of bandwidth?

* Do I risk anything else?


Thank you in advance for any comments/suggestions about this topic.


Christophe