3Com 4.2.2 manual Integrated ATM/Ethernet Switching

C-6APPENDIX C: ATM AND VLAN MANAGEMENT BASICS

Table C-2Comparison of SVC and PVC

SVC	PVC
Supported by signaling standard	Supported by MIB or other
	management entity

Integrated ATM/Ethernet Switching

ATM Backbone Network When Ethernet LANs are connected through a conventional switching hub or backbone, the bandwidth provided is restricted to the data rate of the Ethernet or FDDI technology running on it. If, instead, the Ethernet LANs are connected through an ATM backbone switch - creating an integrated ATM/Ethernet network - the bandwidth bottleneck is opened up and performance is increased across the combined network. The Ethernet switches pass only those messages whose sender and receiver are in separate Ethernet LANs to the ATM Switch, thereby reducing the message traffic on the combined system. Furthermore, the high-speed switching rate and efficient time-utilization of ATM are responsible for the high throughput of the ATM/Ethernet network system.

The ATM/Ethernet network system also opens new possibilities in network design. Instead of being restricted to LANs, whose users are connected by a physical cable, new efficient LANs can be created which cross physical LAN boundaries. The sophisticated address handling of ATM allows related users in separate physical LANs to be effectively grouped into a common broadcast domain called a Virtual LAN. Virtual LANs are described in the next section.

Virtual LAN Basics Just as an Ethernet LAN enables a group of stations to communicate efficiently on a common physical bus, so new networking technology such as ATM makes it possible for stations on different LANs to communicate with almost the same efficiency, even when separated by great distances. This allows network managers to group remote stations that need to communicate frequently into a common high-bandwidth broadcast domain called a Virtual LAN. For example, marketing department personnel who happen to work in different physical locations could be formed into one Virtual LAN and engineering department personnel into another. The term “Virtual LAN” is used because communicating stations continue to transmit and receive as though they were on the same physical Ethernet LAN. In this manual, the abbreviated expression “VLAN” is used for a Virtual LAN.