Handbook of Local Area Networks, 1998 Edition:Applications of LAN Technology Click Here! Search the site:   ITLibrary ITKnowledge EXPERT SEARCH Programming Languages Databases Security Web Services Network Services Middleware Components Operating Systems User Interfaces Groupware & Collaboration Content Management Productivity Applications Hardware Fun & Games EarthWeb sites Crossnodes Datamation Developer.com DICE EarthWeb.com EarthWeb Direct ERP Hub Gamelan GoCertify.com HTMLGoodies Intranet Journal IT Knowledge IT Library JavaGoodies JARS JavaScripts.com open source IT RoadCoders Y2K Info Previous Table of Contents Next Evolving Bandwidth Management Protocols From an integration perspective, however, one of the most important advantages of planning the network using IP is that IP as well adapted to LAN as WAN environments. DVMRP. At the network architecture level, prioritization schemes in the IP specifications issued by IETF working groups hold the greatest promise for improved management and distribution of video over IP networks. In the late 1980s, the IETF ratified the distance vector multicast routing protocol (DVMRP) to transport live video feeds in IP multicast mode over the Mbone. DVMRP works by essentially “flooding” all available routes with a broadcast message, something which could be tolerated more easily before the Internet grew in popularity. IPv5, or Streaming II Protocol. About the same time DVMRP was introduced, the Streaming II (ST-II) protocol was proposed by Bolt Beranek and Newman (BBN). A connection-oriented routing protocol, ST-II is used in end-point and router software and offers a call setup facility that lets the originator control bandwidth in a video and audio session by allocating bandwidth through the router upon request. Virtual links are established for the duration of the session and resources are allocated along the virtual links. ST-II—also known as IPv5 and sometimes called ST-II+—is evolving to address connection setup delays and options for allowing both receivers and senders to open sockets without a conference administrator’s approval. Today’s version of ST-II+ is not backward-compatible with ST-II. Protocol Independent Multicasting (PIM). To address the inherently “unscalable nature of DVMRP,” the PIM system was proposed in 1994. This protocol designates so-called rendezvous points for registration of both senders and receivers of multimedia multicasts. Because the protocol (implemented in routers such as those shipping from Cisco Systems) is not restrictive, it also works with any unicast routing protocol (as in the case in a private videoconference over an IP WAN). Dense mode PIM—which applies where the volume of multicast traffic is high and senders and receivers are in close geographic proximity to one another—uses reverse path forwarding and operates much like DVMRP. RSVP. The bandwidth management protocol with the most enthusiastic following to date is known as the reservation protocol (RSVP). Implemented in end-point and router software on the Mbone and currently under review for IETF ratification, RSVP guarantees bandwidth allocation in connectionless networks according to a receiver-driven model. RSVP is fixed-bit-rate allocation, with routines to handle available bit rate in the future. It is also technology independent and can run on ISDN and private network connections such as Ethernet-based intranets. Prototype support for RSVP has been demonstrated by several different router vendors and will be available in many products by mid-1997. With these new products, RSVP will be quickly deployed throughout intranets, although it is unlikely that the same protocol will be deployed throughout the Internet until at least a year later. Billing and Related Issues In addition to the impediments cited so far—namely, complex management challenges associated with video— current Internet pricing models do not reflect guaranteed bandwidth allocation. As a result, most commercial Internet service providers will be reluctant to implement RSVP in their routers because in using this protocol, a few users could potentially monopolize router resources without appropriately compensating the service provider. New research at BBN and in the IETF’s Internet Services Working Group promises to address the problem with specific billing protocols built into end-points and routers. Researchers at the University of Illinois-Champagne are exploring a solution to circumvent the successive layers of management code over IP. The video datagram protocol (VDP) eliminates TCP and works at the IP level to move video, audio, and data simultaneously. The protocol itself addresses the delivery timing issues by dynamically using a best-effort adaptive flow control methodology. Previous Table of Contents Next Use of this site is subject certain Terms & Conditions. Copyright (c) 1996-1999 EarthWeb, Inc.. All rights reserved. Reproduction in whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Please read our privacy policy for details.