Bandwidth Constraints model

["Francois Le Faucheur (flefauch)" <flefauch@cisco.com>]

Title: Message

Hello,

 

Quickly went through the thread we had on BC models before/during Yokohama. My take on it is that:

 

1) There is some concensus on BC Model objectives:

    -i- it should be possible to disable preemption as some network may not want to use preemption
    -ii- when preemption is disabled, the Model should still work "reasonably" well.
    -iii- there should be effective use of bandwidth (ie good bandwidth sharing among CTs).
    -iv- there should be some isolation (ie a CT cannot hogg the bw of another CT).
    -v- there should be protection against QoS degradation (at least of the premium CTs e.g Voice, Premium Data...).
    -vi- the BC model should be reasoanly simple and shouldn't require additional IGP extensions.

 

2) Maximum Allocation Model (MAM) :

    - MAM is "intuitive"/easy to conceptualise

    - In environments where preemption is not to be used, MAM is attractive because:

        * it is good at achieving isolation.

        * if one doesn't worry too much about "QoS degradation" of lower/medium classes, then MAM can achieve reasonable bw efficiency.

    - it cannot simultaneously achieve isolation, bw efficiency and protection against QoS degradation

 

3) Russian Dolls Model (RDM):

    - In environments where preemption can be used, RDM is attractive because it can simultaneously achieve Bw efficiency, isolation and protection against QoS degradation (ie -iii-, -iv- and -v-)

    - in environments where preemption is not to be used, RDM cannot achieve good isolation.

 

4) Other Models:

    - Jerry indicated it is actually possible to achieve -iii-, -iv-, -v- without preemption and will document another BC Model (maximum allocation with reservation (MAR)) which achieves this.

 

Are we in synch?

 

Cheers

 

Francois