Subject: Differential Services waypoint

From: [email-masked]
Date: Fri, 17 Oct 1997 11:57:55 -0500

I have seen a lot of good technical discussions on various aspects of 
     a simplified QOS/differential services solution on this list, but am 
     interested in getting a more complete picture.

     1. I am assuming that there is general list agreement on the need for 
     a simpler version of providing network operators with the ability to 
     offer differential services.(Simpler than RSVP I think RSVP is still 
     the ultimate way to go, but that today's routers, due to cost points, 
     don't have enough CPU power beyond their packet forwarding 
     requirements to implement RSVP.) This simpler solution needs to be 
     ready ASAP, or we will face a flood of non-interoperable solutions. 
     The market place is ready now. I'd like to see a draft of some sort 
     ready for Washington.

     2. I believe that most of the list agrees with Fred that precedence 
     and a fair RED algorithm are the way to go for grooming inbound 
     traffic at the "edge" of the network. I define edge to be the first 
     hop router encountered by the client.( fyi - In addition to the 
     Lin/Morris FRED paper,"Dynamics of Random Early Detection", a 
     Floyd/Fall paper, "Router Mechanisms to Support End-to-End Congestion 
     Control" also offers a fair RED based on a combined metric and a good 
     discussion on low overhead flow identification.) This combination 
     provides relatively well groomed input to the net. 
     
     3. The current list"s area of contention appears to be how to handle 
     the traffic interface that connects to the "bulk" of the internet. 
     Weighted and Stochastic Fair Queuing have been proffered, along with 
     the Drop Precedence(DP) bit(s), as possible aids in this area. 
     
     3a. SFQ and WFQ - Because WFQ and SFQ are methods used to shape 
     traffic, let's agree that they should be used only at the edge.
     
     3b. Dropping packets is a waste of bandwidth on any link, but it gets 
     more expensive the further they progress through the network. Let's 
     use a single DP bit beyond the edge and use the hop count as the drop 
     preference. The higher the hop count, the lower the drop 
     preference(discard something else first). Getting network 
     understanding/agreement of multitiered drop preference doesn't seem 
     to buy much in light of the complexity introduced.
     
     4. Trying to offer latency guarantees/values seems to be a bit far 
     fetched in light of the variability of the internet fabric(e.g.. frame 
     sizes on WAN links).  I don't want to go through the exercise of 
     complicating this simplified QoS solution with a negotiable parameter 
     only to find that, in practice, it's of no value. A real time/ 
     non-real time bit would be useful to allow routers that support 
     it(real-time and non-real time queues) to behave properly in 
     conjunction with the DP bit and hop count.
     
     5. Billing for differential services has to be done at the ingress 
     edge for now. The idea of a billing system throughout the network is 
     great in theory, but needs a lot of careful work and input from the 
     service providers/operators. Let's not try and put any signaling 
     schemes for billing in this simplified QOS system(SQOS). In fact, if 
     we avoid signaling schemes/information sharing altogether, the 
     likelihood of having the SQOS work with older gear is virtually 
     assured. The packet needs to carry all the information that is 
     required. 

     Ken Peirce

---

From: Fred Baker <[email-masked]>
Date: Fri, 17 Oct 1997 11:04:05 -0700

At 11:57 AM -0500 10/17/97, [email-masked] wrote:
>the edge.

which edge? The edge of each of the backbones a message crosses? The edge
of one of the layered ISPs that fed it to those backbones? The edge of the
company? The edge of the LAN that the fellow is attached to?

I think conceptually you're probably right, but identifying the point
you're talking about is not so easy.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
  "A beautiful idea has a much greater chance of being a correct idea
   than an ugly one."
                     -- Roger Penrose, "The Emperor's New Mind", 1989