Sun Microsystems SunLink SNA 9.1 PU2.1, Руководство по настройке

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D-8 SunLink SNA 9.1 PU2.1 Server Configuration Guide—August 1997
D
the ring station. To have a multiple-ring transmission occur, the originating
ring station inserts source routing information into the frame. The presence of
source routing information is indicated by bit 0 of byte 0 of the MAC source
address being set to 1. The source routing format is shown in the following
figure.
Figure D-5 Source Routing Format
The first two bytes of a source route are the routing control field. This field
identifies the type of route used, the total length of the source routing
information, the direction of the route with respect to the originating station,
and the largest frame size that can travel over the route.
Following the routing control field are zero to eight optional 2-byte segment
number fields. The segment number fields consist of a ring number identifier
and a bridge number identifier. Each ring in a multiple-ring network must be
uniquely numbered, and individual bridges between the same two rings must
be individually numbered. Bridges that connect different rings can have the
same number. However, Sun recommends that bridge numbers are also
unique.
The following types of source routes are used in an IBM Token Ring network:
•
Nonbroadcast - Used when a route is known to a ring station on a remote
Token Ring network. The originating station transmits the frame with the
nonbroadcast source route attached. The Token Ring bridge, depending on
how it is configured, optionally transmits the frame on its second ring.