Related Links IP Multicast Gigabit Ethernet External Link IEEE Catalog

Packet™ Magazine Archives, Fourth Quarter 1998 Multicast Standards Taking Shape With distance learning and other multimedia applications rapidly gaining popularity, users await an open-standards approach for multicast routing. Growth in implementation has driven the quest for more efficient, scalable multicast mechanisms. Recently, one such mechanism co-authored by Cisco engineers cleared another hurdle on the path to becoming an Internet standard when the IETF issued RFC 2362, Protocol-Independent Multicast, Sparse Mode (PIM-SM). The global IP Multicast Backbone now uses PIM for most connections and major Internet service providers (ISPs) are beginning to offer PIM-based multicast. Cisco IOS® software supports interoperability between both sparse-mode and dense-mode PIM and the traditional Distance Vector Multicast Routing Protocol (DVMRP). In addition to PIM protocols, Cisco products also support Internet Group Management Protocol Version 2 (IGMPv2), IGMP snooping, and ATM interoperability More information is available from Cisco's IP Multicast page. True Ethernet at Gigabit Speeds The recently ratified IEEE 802.3z standard defines Gigabit Ethernet with backward compatibility for seamless integration with the vast installed base of 10- and 100-Mbps Ethernet networks and systems. "Gigabit Ethernet is truly Ethernet," says Howard Frazier, a Cisco engineer who chaired the IEEE 802.3z Gigabit Task Force. "All speeds use the same frame format and frame sizes, and we preserved the management parameters already familiar to network administrators." Gigabit Ethernet is the most cost-effective high-bandwidth LAN, requiring no additional investment in protocol stacks or middleware. It is well suited for backbone connectivity between 10/100BaseT switches, connection to high-performance servers, or a migration path to connect high-end desktop computers above 100BaseT. The 802.3z specification includes full- and half-duplex operating modes. For speed and simplicity, most installations are likely to use full duplex (no collisions, no contention), which supports router, switch, and end-station connections. The 802.3z specification supports these distances for physical media: Single-mode fiber -- to 5 km Multimode fiber -- to 550 meters Shielded copper cable -- to 25 meters Category 5 UTP cable -- to 100 meters, to be supported by IEEE 802.3ab, 1000BaseT Exceeding these specifications, Cisco products use 802.3z-compliant 1000BaseLX/LH optical components to support spans of single-mode fiber up to 10 km. The full text of the 802.3z standard is available for purchase from the IEEE. Cisco's Gigabit Ethernet page also offers technical briefs and white papers. Modular Choices for Upgrade Flexibility Using industry-standard, hot-swappable Gigabit Interface Converter (GBIC) modular technology, Cisco products can intermix any combination of 802.3z-compliant 1000BaseSX or 1000BaseLX/LH interfaces on a port-by-port basis. This modular approach makes it easy to upgrade to the latest interface technology. Table of Contents Posted: Thu Feb 4 17:10:37 PST 1999 Copyright © 1998 Cisco Systems, Inc.