Brian E Carpenter <brc@xxxxxxxxxxxxxx> wrote on 11/14/2006 11:36:40 AM: > ... > > This illustrates some of my concerns about this requirements work being > done outside the IETF. > ... > > 2. The notion that solutions such as precedence and preemption > are (a) requirements and (b) applicable to all applications just > doesn't compute for me. We'd actually need to understand at a more > basic level what the functional requirements are, in terms that are > meaningful for a datagram network. I don't believe that will > happen in ATIS or ITU-T. > > Brian (personal opinion) > Exactly. In the circuit switched world, a circuit is either up or down, and "preemption" means taking the circuit down. But in the IP world, there is a full continuum of states in between. Some of these are candidates for a useful service, and some of which aren't. The understanding of this continuum, and of the (intended and unintended) consequences is much stronger in the IETF than in the historically-circuit-switched world. Some of the possibilities in that continuum include (in no particular order): - Allowing extra sessions in, and permitting degradation in QoS across all sessions. - Allowing a higher packet drop rate across all the "lower priority" calls. - Negotiating a lower bandwidth allocation, possibly accompanied by a changing to a lower rate bandwidth codec when a higher priority session needs to "preempt". - Negotiating (or arbitrarily imposing) a different PHB (e.g. AF or BE rather than EF) for lower priority sessions when a higher priority session needs to "preempt". - Different Capacity Admission Control mechanisms for different priority sessions. The analysis/understanding of these (and other) alternatives is much better done in the IETF than in the historically-circuit-swiched SDOs. Janet > _______________________________________________ > Ietf mailing list > Ietf@xxxxxxxx > https://www1.ietf.org/mailman/listinfo/ietf _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf