Sun Microsystems 3U manual Classical IP and LAN Emulation Protocols, ATM Network Protocols

C H A P T E R 7

Classical IP and LAN Emulation

Protocols

This chapter describes ATM protocols and how they are supported by the SunATM software. This chapter is composed of the following sections:

■“ATM Network Protocols” on page 65

■“ATM Addresses and Address Registration” on page 66

■“Classical Internet Protocol” on page 67

■“LAN Emulation” on page 69

ATM Network Protocols

ATM is a connection-oriented network protocol, which means that a connection must be established between two communicating entities before data transfer can begin. IP is inherently connectionless. The implementation on the host must therefore reconcile the differences in these two paradigms.

There are two standard ways of doing this: Classical IP, standardized in RFC 1577, and LAN Emulation, standardized in the LAN Emulation 1.0 specification from the ATM Forum. The SunATM architecture supports both of these methods. This chapter discusses some of the key ideas of these two methods.

Both methods allow IP to run transparently over the ATM interface. Thus IP itself sees the ATM interface just as it sees any traditional network interface. Every SunATM interface has a subnet IP address. As an ATM interface starts up, appropriate modules and drivers are plumbed. All the TCP/IP and

UDP/IP applications run without modifications over these modules, and all the utilities associated with the network interfaces also run without modification and display similar results (for example, netstat and ifconfig utilities), with one exception. Because of the different plumbing of the ATM modules, the plumb and unplumb options of ifconfig will not work on ATM interfaces. The atmifconfig(1M) command may be used to plumb and unplumb ATM interfaces. IP treats the ATM interface as a subnet, choosing the interface used to send a packet out based on the IP address of the destination and on the IP address and netmask of the interface itself.

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