All, We recently implemented iPCRF on our EPC to great effect. We added a QCI 1 profile that we apply to our dedicated bearer, and are prioritizing our VoIP service using that. So that we can easily see and verify the effectiveness of this, we also started sending ICMP over the same dedicated bearer. Average latency and jitter to CPEs dropped like a rock right after we did that, so it is clearly working.
When our ENBs start to become moderately busy, we still notice that RTT for traffic on the default bearer can become both exceptionally latent and jittery. This is easy to see if we run a constant ping to a CPE and then stop prioritizing ICMP to that CPE in the middle of the ping test. Ping jitter goes up significantly almost immediately. When we prioritize ICMP, all we end up doing is masking that problem. Unfortunately, release 6.6 only allows for one dedicated bearer, so we can't classify different types of traffic across multiple QCI levels in order to try to help deal with this better. But after looking at the various QCI levels that are defined in the LTE spec (https://en.wikipedia.org/wiki/QoS_Class_Identifier), I am wondering if there isn't a short-term answer to this problem while we wait for multiple dedicated bearer support. Specifically, I see that each level also has a defined "packet delay budget". QCI 6, the default pick for the default bearer, has a PDB of 300ms. What would happen if we were to, say, switch to using QCI 7, which has a PDB of 100ms, for our default bearer? Would we actually see an overall improvement in RTT? And if so, would it be at the expense of anything/what would be the downside(s)? (For example, would overall throughput end up taking a hit because it is trying to service UEs less efficiently so that it can make good on the latency budget?) I'm curious to know if anyone has tried this. Thanks, -- Nathan Anderson First Step Internet, LLC [email protected] _______________________________________________ Telrad mailing list [email protected] http://lists.wispa.org/mailman/listinfo/telrad
