Multimedia over IP: A new choice?

ATM is being touted as the ultimate solution for multimedia applications because it can tailor different levels of quality of service to individual service applications, be they voice, video or data. But now, with Internet usage growing exponentially, the Internet protocol community wants a piece of this multimedia action, too. So the question of the day is: How much will these new requirements affect carrier implementations of network platforms and services to support multimedia? The Internet Engineering Task Force, which, as the name implies, focuses on the development of Internet technology, is currently working on a new set of standards that would give IP networks the same QoS that exists in ATM. A key part of this standards effort is the Resource Reservation Protocol (RSVP), which allows applications to reserve bandwidth on the network. It's simply a mechanism to make a reservation, but guaranteeing that reservation will depend on whether the network will support and deliver the desired bandwidth. Since an IP environment is connectionless-packets transferred between two locations may take different paths-it can be more of a challenge to guarantee bandwidth, compared with ATM where the paths are pre-defined. To meet the IETF mandate for IP QoS, IP equipment will have to perform some of the following functions: * Identify the different incoming traffic types using source and destination addresses, port number and protocol types. * Fragment the frames to reduce delay and jitter. Frame fragmentation minimizes the likelihood of a delay-sensitive voice frame being stuck behind or delayed by a long data frame. * Assign the traffic to the appropriate priority queue. The parameters for the queue are defined based on the QoS needed by the application. * Send signaling information to other equipment on the network to make sure that the traffic is handled appropriately throughout the network. To assure performance, IP equipment vendors may need to implement these new standards with software and/or hardware upgrades. Whether end users want to do multimedia over IP, ATM, or both, it's the carrier's job to support it over a public network. Ironically, while end-to-end QoS can be addressed more easily in cases where ATM is used at the desktop, at this point, few users have ATM networks that reach this far into their organizations. IP and Ethernet seem to have won out in the desktop and LAN arenas, with ATM in the wide area network. With IP standards for multimedia, end users may not have to make the leap to desktop ATM just yet, hence protecting their current investments. Does this mean that carriers would have to implement IP-based networks to support customers that run multimedia over IP to guarantee end-to-end (desktop-to-desktop) QoS? The biggest issue that carriers need to consider with IP networks is scalability. If the carrier already has an IP network to deliver Internet access, supporting multimedia on this network may be a good interim solution. Yet carriers must ascertain if the IP network can scale to meet the traffic volumes of a carrier's public service in the long run. Another solution is for carriers is to use ATM on the backbone. This certainly minimizes the concern of scalability. The issue here, however, is how to map a user's multimedia IP QoS to the carrier's ATM QoS. There are some vendor-specific solutions in the works to provide this functionality, but there aren't any standard nor generally available products that can do this mapping today. The good news is that there are vendors that attend both the IETF and the ATM Forum working groups to drive complementary solutions between IP and ATM. Multimedia over IP could be a good thing for public ATM services. It's another enabler for the multimedia market in need of a jump-start. However, vendors need to be careful in creating controversy by positioning the issues as IP vs. ATM, rather than positioning one as being more appropriate for specific situations than the other. Controversy may confuse the market and stagnate growth. Java and the emergence of multimedia applications on the World Wide Web are also fueling the fire for multimedia adoption. But the real questions are: When and will end user demand, vendor solutions, and carrier services for multimedia all converge at the right time to drive critical mass? Liza Henderson is a Broadband Consultant with TeleChoice, Verona, N.J. Her e-mail address is lhenderson@telechoice.com.