Handbook of Local Area Networks, 1998 Edition:LAN Interconnectivity Basics 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 SNA Internetworking RFC 1490 is not limited to use for IP and Internet Packet Exchange (IPX) LAN internetworking. Because of networking equipment vendors’ continuing efforts to provide effective internetworking solutions for IBM SNA users, another vendor-sponsored group was started: the 1490 Market Development Group. This group, which includes the networking consultancy NetResults and several vendors of multiprotocol-capable frame relay access devices and other networking components (e.g., Andrew, Eicon, FastComm, Motorola, Netlink, Presticom, Source-Comm, and Sync Research), sponsors seminars on the uses of RVC 1490 for networking over frame relay as an alterative to traditional IBM SNA/SDLC networking (usually over leased lines) or other, newer methods such as data link switching (DLSw), which is endorsed by router vendors Bay Networks, Cisco, Proteon, and others. Because of the addition of direct frame relay support to IBM front end-processors starting with Network Control Processor version 6.3 through the more recent versions 7.1 and 7.2, and also AS/400 midrange computers in recent OS/400 releases, it is now possible to use frame relay for streamlined SNA communications. Customers incur less overhead with encapsulation of SNA in IP compared with DLSw. Because both the front-end processor and AS/400 can communicate over frame relay, only remote sites need frame relay access devices to provide the means to communicate over the wide area. A central site router and the additional bandwidth required by encapsulation in IP are not necessary. RFC 1490 versus DLSw As illustrated in Exhibit 3-4-4, DLSw can also be transported over frame relay when the IP carrying the information is routed over frame relay (using RFC 1490). Each technology has its advantages and disadvantages and can be used beneficially in different applications. Exhibit 3-4-4.  RFC 1490 and Data Link Switching Over Frame Relay DLSw is often suited to environments where the core network of the organization is already an IP internetwork. When IP is not the core, it makes sense to examine RFC 1490-style networking, because significant bandwidth and equipment savings can result. Likewise, when Token Ring is used instead of serial SDLC (synchronous data link control) communications, as is the case when using source route bridging, frame relay can also be used advantageously to carry the wide area communications between the bridges. FRAME RELAY AND ATM: COOPERATION, NOT COMPETITION Another new technology has risen to the attention of the media and the market: asynchronous transfer mode. ATM is often described as the next wave in networking technology because of its applicability to both local and wide area communications and its potential for carrying data, voice, and video. Paralleling the developments in frame relay, there is currently a fast-growing ATM Forum with an associated user group known as the ATM Enterprise Roundtable. The ATM Forum now numbers more than 900 members (including companies and organizations). Many users and media analysts became concerned that the arrival and popularity of ATM would affect frame relay, possibly even making frame relay obsolete. Potential end users of frame relay may ask whether they should make an investment in frame relay or simply wait for ATM. To further complicate the situation, just as frame relay was gaining momentum and ATM was emerging, switched multimegabit digital service (SMDS) offerings, supported by Bellcore, were also being touted by several local and long distance carriers. The facts concerning the simplicity of implementation and relative low cost of frame relay have helped to ensure its place in the corporate network. However, many of the players in the development of frame relay have also been involved in ATM, and some have an interest in SMDS as well. There have been cooperative education efforts by the ATM Forum and Frame Relay Forum, various consultants and analysts, and Bellcore. Frame relay and ATM will most likely coexist within the networking hierarchy. A situation that already exists behind the scenes at some carriers is frame relay feeding ATM (discussed in more detail later in this chapter). The Current Standings Frame relay services are available and attractive in price, and many businesses are running their corporate communications over frame relay. Usage of ATM for LANs and in campus environments is beginning to happen. However, this LAN deployment of ATM has been impacted by Switched and Fast Ethernet products and the promise of Gigabit Ethernet. In the wide area, however, most carriers have not yet fully deployed nationwide or international networks. Some standards work remains to be finalized. It would appear—for a variety of reasons, most of which relate to cost and the speeds typically used in networking today—that at or below T1/E1 speeds (i.e., from 56K bps up to 1.5M and 2M bps), frame relay will be the service of choice. At speeds above T1/E1 through T3/E3 and higher (e.g., OC-1 and OC-3), ATM will be the choice—assuming availability and cost-effectiveness of services for new applications that mandate network bandwidth (more about the impact of ATM in a later section of this chapter). What About SMDS and ISDN? In the case of SMDS, the offerings and pricing were too little and too much, respectively, when compared to frame relay. Though services are available, unless SMDS is reborn as a future ATM access gateway—much in the way that ISDN appears to be reemerging in North America as a technology for feeding frame relay and Internet services—it would appear that SMDS will remain in the minority in most of the world (with several countries such as Germany and Australia being notable exceptions). Customers should, however, remember that outside the North American market, ISDN is quite popular and has widespread availability. ISDN is a practical technology, and with increasingly attractive pricing in the US, over the next few years it may become as widespread in North America as it is overseas. ISDN, as noted previously, is taking hold as an excellent feeder technology for medium to large networks using frame relay, in addition to being a book to lower-speed (64K to 128K bps) switched connectivity for smaller networks or for on-demand services. 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.