Subject: QoS support in end hosts

From: Ashish Mehra <[email-masked]>
Date: Sun, 18 Aug 1996 00:04:53 -0400 (EDT)

I am taking the liberty of posting this email to these
lists in the belief that it is of relevance to this
community. Please accept my sincere apologies if 
that is not the case. 

I would like to bring to your attention the following 
papers focusing on communication support needed in the
end hosts to provide quality of service guarantees.
While the papers do not directly target the Internet,
the issues explored and solutions suggested can be 
applied to the design of communication software for 
Internet hosts (such as Web clients and servers) as 
well. A short summary of each paper is provided to 
highlight relevance to the provision of Integrated 
Services on the Internet.

1. Ashish Mehra, Atri Indiresan, Kang Shin,    
   "Resource Management for Real-Time Communication: 
   Making Theory Meet Practice," Proc. of 2nd Real-Time
   Applications and Technology Symposium, pp. 130--138, 
   June 1996.

   Focuses on admission control extensions to account for 
   protocol processing (fragmentation), implementation overheads 
   (context switching, cache misses, transmission-completion 
   interrupts, link scheduling), and the overlap between CPU 
   processing and link transmission. Only send-side communication 
   processing is considered (i.e., applicable to Web servers) and 
   the model for QoS communication is based on real-time channels, 
   a paradigm for guaranteed-QoS communication in packet-switched 
   networks. 

   The real-time channel model is similar to the QoS model being
   considered for integrated services on the Internet, although 
   only unicast communication is considered. In addition to end 
   hosts, the proposed admission control extensions may also be 
   applicable to routers that perform fragmentation to reconcile 
   differences in the MTU sizes on the attached incoming and 
   outgoing networks. 

2. Ashish Mehra, Atri Indiresan, Kang Shin,    
   "Structuring Communication Software for Quality-of-Service 
    Guarantees" To appear Proc. 17th Real-Time Systems Symposium, 
    December 1996.  

   While the first paper considered admission control (performed 
   during signalling), this paper focuses on data transfer once 
   signalling has successfully established a real-time channel. 
   A process-per-channel model of protocol processing is proposed 
   and implemented in an x-kernel communication executive; this 
   extends the process-per-message and process-per-connection 
   models proposed earlier in the literature. The design is based 
   on three key goals:
        - maintenance of per-channel QoS guarantees
        - overload protection between channels, and
        - fairness to best-effort traffic
   Various architectural features include per-channel "handlers" 
   with message and packet FIFO queues, cooperative preemption 
   between handlers, and earliest-deadline-first CPU and link 
   scheduling.  

   The x-kernel protocol stack adopted does not employ the TCP/IP
   protocol suite. However, the proposed software architecture 
   is relatively independent of the network and transport layer 
   protocols used, as long as a connection-oriented protocol 
   stack can be realized. The paper does not consider the issues 
   involved in integration with applications and the rest of the 
   host operating system. 

The postscript files are available from 
http://www.eecs.umich.edu/~ashish.
Any feedback (comments, criticism) would be greatly appreciated.

Thanks,

Ashish Mehra
(Graduate Student
Real-Time Computing Laboratory
University of Michigan at Ann Arbor)