Hi, Dhruv: My take to this is what we specify is cost metrics between endpoint to endpoint or between PID and PID, shall we need to distinguish whether a cost metric is end to end cost or link cost, to me E2E cost and link cost are both path metric, the different is one is whole path metric while the other is sub-path metric.
Yes, users may only care about end to end cost metrics, but sub-path can be used as filter or constraint to select a best path. From this point view, end to end cost metrics should definitely be mandatorily supported (e.g., delay, jitter, packet loss)while sub-path metric is optionally supported(e.g.,available bandwidth). In addition, we also have bandwidth metric to be defined in this draft, shall we view this bandwidth metrics as end to end path metrics and set it to mandatory? E.g., from application point of view, we have upstream bandwidth or downstream bandwidth, I think both are end to end path metrics. Regards! -Qin -----邮件原件----- 发件人: alto [mailto:[email protected]] 代表 Dhruv Dhody 发送时间: 2014年7月22日 8:23 收件人: Qin Wu 抄送: [email protected] 主题: Re: [alto] statistics operators for ALTO cost metrics Hi Qin, One point to note that would be that metrics in IGP drafts are in terms of a TE link, in ALTO we need to worry about E2E cost ( or cost of an abstract link incase when ALTO also convey an abstract topology), so these cost metrics are composite metrics. ALTO server may rely on database populated by routing protocols, or a PCE, or a measurement system. Thus ALTO server rely completely on the source on how this cost metric is derived and all it can do is to specify the source (or composition mechanism) in its reply. Bandwidth is a bit different from the delay, jitter and loss which can be easily composed to an end to end metric. Bandwidth is well suited to filtering to get endpoints that can provide the requested bandwidth. As a cost it might either represent the bottleneck link for the E2E path. Question for us to consider is - do we need all of max bandwidth, max resv bandwidth, available bandwidth etc; and what format they should be in. Dhruv On Fri, Jul 18, 2014 at 8:13 AM, Qin Wu <[email protected]> wrote: > Hi, > > Motivated by RFC3630 and draft-ietf-isis-te-metric-extensions, we > define 11 alto cost metrics, > > The value of these alto cost metrics are high aggregated value, we may > have several statistics operators, e.g., > > Mean, variance, avg, percentile). > > In the current draft, delay and delay jitter are both on delay, we use > mean > > For delay and use variance for delayjitter. > > It is not clear these statistics operator are appropriate for them? > E.g., should we use percentile for bandwidth related cost metric? > > Any opinion? > > > > Regards! > > -Qin _______________________________________________ alto mailing list [email protected] https://www.ietf.org/mailman/listinfo/alto _______________________________________________ alto mailing list [email protected] https://www.ietf.org/mailman/listinfo/alto
