The route distinguisher (RD) is an 8-byte value consisting of 2 major fields, the Type field and Value field, as shown in the following figure. The Type field determines how the Value field should be interpreted. The 7210 SAS implementation supports the three (3) Type values as defined in the Internet draft.
The three Type values are:
Type 0: Value Field - Administrator subfield (2 bytes) Assigned number subfield (4 bytes)
The administrator field must contain an ASN (using private AS numbers is discouraged). The Assigned field contains a number assigned by the service provider.
Type 1: Value Field - Administrator subfield (4 bytes) Assigned number subfield (2 bytes)
The administrator field must contain an IP address (using private IP address space is discouraged). The Assigned field contains a number assigned by the service provider.
Type 2: Value Field - Administrator subfield (4 bytes) Assigned number subfield (2 bytes)
The administrator field must contain a 4-byte ASN (using private AS numbers is discouraged). The Assigned field contains a number assigned by the service provider.