Subject: doctoral dissertation

From: Ashish Mehra <[email-masked]>
Date: Wed, 24 Sep 1997 18:02:26 -0400 (EDT)

Hi everyone,

FYI, the following dissertation is now available in postscript
from http://www.eecs.umich.edu/~ashish. 

Any feedback/comments are welcome.

Thanks,

Ashish Mehra

=================================================================
Title: 
       Structuring Host Communication Software for 
       Quality of Service Guarantees

Abstract:
	
This dissertation addresses several open issues in structuring
communication software at end hosts to provide per-connection QoS
guarantees.  Our primary thrust is on realizing deterministic QoS
guarantees in an experimental setting.

We design a novel QoS-sensitive communication subsystem architecture
that provides components and mechanisms to manage communication
resources in a QoS-sensitive fashion.  This architecture is based on
three key design principles: maintenance of QoS guarantees, overload
protection via per-connection traffic enforcement, and fairness to
best-effort traffic.  We demonstrate the efficacy of the architecture
via experiments using our xkernel-based prototype implementation.

We develop admission control extensions to capture important
implementation-related aspects not considered by theoretical resource
management policies proposed in the literature.  Communication
performance is significantly affected by implementation-related
aspects such as preemption overheads and constraints, simultaneous
management of CPU and link bandwidth, link scheduling paradigms at
sending hosts, and packet input mechanisms at receiving hosts.

We build a full-fledged guaranteed-QoS communication service on a
contemporary microkernel operating system using a new service
architecture integrating a QoS-aware application programming
interface, a reliable signalling and resource reservation protocol,
and QoS-sensitive data transmission and reception.  We develop
architectural and admission control enhancements that capture new
overheads and constraints imposed by a microkernel server
configuration.  The service is implemented and evaluated on
Pentium-based PCs running OSF MK 7.2 and communicating across switched
Ethernet.

To enhance the portability of guaranteed-QoS communication services,
we design self-parameterizing protocol stacks that can parameterize
themselves appropriately during data transfer.  We experimentally
evaluate a self-parameterizing guaranteed-QoS communication service to
demonstrate the feasibility of our approach.  Self-parameterizing
protocol stacks are a natural way to design portable QoS-sensitive
communication software.

To provide ``better than best-effort'' Internet connectivity, the
performance impact of supporting integrated services in TCP/IP
protocol stacks must be assessed.  We have designed, implemented, and
evaluated an RSVP-based QoS architecture for TCP/IP protocol stacks
supporting an integrated services Internet.  Using detailed
kernel-based profiling of RS/6000-based servers running AIX 4.2, we
explore the performance impact of QoS support in TCP/IP protocol
stacks.

We conclude by outlining strategies for integrating QoS-sensitive
communication subsystems with QoS-sensitive application scheduling
policies within host operating systems.