3.3.5.1 Receiving a BecomeBackup Frame

The local master browser server MUST send a BecomeBackup frame to a potential browser server when it determines that the number of current backup browser servers for the machine group on the local master browser server's subnet does not meet the criteria as specified in section 3.3.5.7.

A browser server that receives a BecomeBackup frame MUST attempt to become a backup browser.

If the browser server is incapable of becoming a backup (for example, because it is overloaded), the browser server MUST shut down as specified in section 3.3.7.

If the browser server does not recognize the name of the local master browser for its machine group, it MUST start the FindMaster timer and send an AnnouncementRequest frame request by issuing a mailslot write as specified in [MS-MAIL] section 3.1.4.1, passing in the following parameters.

Parameter name

Value

NetBIOS name of the remote server

<Machine Group Name>[0x1D]

Mailslot name

\MAILSLOT\BROWSE

Data

AnnouncementRequest as specified in section 2.2.2.

The server SHOULD continue processing as described below even if the send fails.

If the FindMaster timer expires before the server receives a LocalMasterAnnouncement frame, the browser server MUST issue another AnnouncementRequest frame request to <Machine Group Name>[0x1D] and reset the FindMaster timer. If the server issues an implementation-defined number of FindMaster frame requests without receiving a LocalMasterAnnouncement frame response, then the server MUST send a RequestElection frame as specified in section 3.3.5.11.

The server SHOULD continue processing as described below even if the send fails.

For more information on the election process, see section 3.3.5.8.<49>

The browser server MUST set Current Role to backup browser server. The browser server MUST enable advertising of the backup browser service as specified in [MS-SRVS] section 3.1.6.9, passing  SV_TYPE_BACKUP_BROWSER as the input parameter. If the browser server does not have a server list, it MUST attempt to retrieve a list of servers from the master browser for the machine group. If successful, the new backup browser MUST immediately send a HostAnnouncement Frame as specified in section 3.2.5.2, with the Flags field in the announcement reflecting the new state of the browser.<50>

The server SHOULD continue processing as described below even if the send fails.

Note that after the master browser receives the HostAnnouncement frame, it MUST hand out this browser server name in GetBackupListResponse frames, and clients will contact this browser server as if it were a backup browser server.

A nonbrowser server that receives a BecomeBackup frame MUST ignore the frame, as specified in section 3.2.5. Similarly, a browser server whose Current Role is equal to backup browser server receives a BecomeBackup frame MUST ignore the frame.

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