Distributed Delay Jitter Control in Packet-Switching Internetworks

			     Domenico Ferrari

				 ABSTRACT


	     Delay jitter is the variation of the delays with  which
	packets traveling on a network connection reach their desti-
	nation.  For good  quality  of  reception,  continuous-media
	(video,  audio,  image)  streams require that jitter be kept
	below a sufficiently small upper bound.  This paper proposes
	a  distributed  mechanism  for controlling delay jitter in a
	packet-switching network. The mechanism can be applied to an
	internetwork  that  satisfies the conditions detailed in the
	paper, and can coexist with  other  schemes  (including  the
	absence  of  any  scheme) for jitter control within the same
	network, the same node, and even the same real-time channel.
	The  mechanism  can  guarantee small jitter bounds even when
	the clocks of the host systems  and  the  gateways  along  a
	channel's  route are only loosely synchronized; furthermore,
	it makes the distribution of buffer space requirements  more
	uniform  over  a  channel's  route,  and  reduces  by a non-
	negligible amount the total buffer space needed by  a  chan-
	nel.   The paper argues that, if these advantages are suffi-
	cient to justify the higher costs of the distributed  jitter
	control  mechanism with respect to a non-distributed one, it
	would be useful to offer to the  network's  users  a  jitter
	control service based on the mechanism proposed here.