ATM Address Formats and Variables (Platform Notes: The SunATM Driver Software)

Platform Notes: The SunATM Driver Software

ATM Address Formats and Variables

ATM addresses, like Network Service Access Point (NSAP) addresses, are 20 octets long, with each octet made up of 1 or 2 hexadecimal digits. The ATM address is divided into three fields: the End System Identifier field, the Selector field, and the Network Prefix field. The End System Identifier (ESI) field is a unique 6 octet value, which can be the IEEE hardware MAC address conventionally associated with every network interface. The Selector field is one octet long. The 13 octets that make up the rest of the ATM address are called the Network Prefix. This field should be derived from the ATM switch fabric to which the interface is connected. Every ATM switch fabric is configured with a 13 octet prefix.

To simplify references to ATM addresses in the SunATM software, several system-defined variables are built into the software. Variables are referenced with the $ operator, as in UNIX shell scripts. Table 2-3 summarizes the system-defined SunATM address variables.

Table 2-3 Predefined SunATM Variables


Variable	Description
`prefix`	The 13-byte prefix associated with the local switch.
`mac`	The 6-byte medium access control (MAC) address associated with the local host or interface.
`sel`	The default 1-byte selector for the local interface.
`macsel`	The concatenation of `$mac:$sel`.
`myaddress`	Concatenation of `$prefix:$mac:$sel`, resulting in the default address for the local interface.
`sunmacsel`N	Concatenation of one of a series of reserved MAC addresses and `$sel` to create a block of reserved ATM ARP server addresses. N should be a decimal number in the range 0 - 199.
`localswitch_server`	Concatenation of `$prefix`, a unique reserved MAC address, and `$sel`. When used as a server address, restricts server access to clients connected to the local switch only.

Note -

The $prefix variable, and any other variables that use it (including $myaddress and $localswitch_server), can not be used on interfaces that are not running ILMI.

ATM addresses are represented by 20 colon-separated octets, with each octet made up of 1 or 2 hexadecimal digits. You can combine variables representing portions of an ATM address with other variables and/or octets to make up a complete address. For example, $prefix:aa:bb:cc:dd:ee:ff:$sel represents a valid ATM address.