[pcp] differentiating traffic, draft-wing-pcp-flowdata

[Dan Wing <[e-mail]>]

Many networks have insufficient access bandwidth and it is desirable to handle flows differently over that access link based on the flow's needs (high bandwidth, low loss, high delay) or if the flow is to a certain device or certain user ((living room television, tablet, mom/dad/kid).  Hosts don't have a way to prioritize flows downstream (towards the host) and have poor capability to prioritize flows upstream, especially among the various hosts on the network.  Various solutions to this problem have been developed over the years (DSCP, RSVP, NSIS) but have drawbacks.

I hope the problem described above resonates with people on this list.  If so, read on.


In draft-wing-pcp-flowdata we propose a solution:  the host describes the flow characteristics to the network and the network indicates its (in)ability to accommodate the flow.  That flow description can be used by the default network, or propagated along the network.  For example in a home network the flow description can propagate from in-home CPE router to the ISP's access router, and in an enterprise network the flow description can propagate within the enterprise network and up to the ISP's access router.  When the flow characteristics are communicated to both sides of a resource-constrained link, the routers on both end can provide different packet forwarding treatment to the flow.

The mechanism draft-wing-pcp-flowdata brings some advantages:

  * incrementally deployable.  This can be implemented entirely within a subscriber's network without participation of their ISP, providing some value (but of course not as much value as being deployed by the ISP's access router).  Similarly, this can be implemented on the ISP's router and the host could signal directly to that ISP's router without needing support of the intermediate network.
  * adaptive bit rate applications can improve user experience by avoiding attempts to exceed the network's upper bandwidth limit
  * traffic differentiation can be per-"event" (e.g., streaming TV of the Olympics, VoIP call with an important customer), in addition to more traditional per-user or per-device or per-application.

Details are in http://tools.ietf.org/html/draft-wing-pcp-flowdata.

Comments welcome.
-d