PRIMECLUSTER Global Link Services Configuration and Administration Guide: Multipath Function (for Solaris(TM) Operating Environment)

B.1.1 Fault Monitoring

In the multipath method, monitor frame is periodically transmitted from the communication path of the "active" state to switches, and the response is monitored. If there is no response from switch, the communication path is change to the "fail" state. And the communication path of "standby" state is changed to the "active" state. Then Line Monitoring is continued.

In addition, when the communication path becomes "fail" state by Link Down detection of cable disconnection etc., it can recover automatically by removing the cause of Link Down (e.g. connect the cable). In the failure monitoring of standby NICs, the link status of the driver that controls a standby NIC is monitored periodically.

• This daemon is supporting IPv4 protocol. It is not supporting IPv6 protocol and FNA protocol, SNA protocol.
• When using ATM cards or FDDI cards, this daemon is not started. The conventional daemon, mpnetd, is started.
• This daemon is not supporting the Multilink Ethernet method. When using Multilink Ethernet method, the conventional daemon is started.

The line monitoring method of two communication paths is shown in "Figure B.1 Line Monitoring of Multipath method (two communication paths)."

[Figure B.1 Line Monitoring of Multipath method (two communication paths)]

When the Multipath method is activated, a monitor frame is periodically transmitted from the online NIC to switch which is connected standby NIC, and the response is monitored. If there is no response from the switch (2) monitoring-count times, this daemon is considered that there are a certain failure is in the route from the online NIC to the switch (2). Next, a monitor frame is transmitted to the switch (1) connected to the online NIC. If there is the response of the monitor frame to switch (1), it can be regarded as the failure of the switch (2), or the failure of the cascade cable between the switch (1) and switch (2). And it continues line monitoring to switch (1). Conversely, if there is no response from switch (1), it considers that the failure of the online NIC, the failure of the switch (1), or the failure of cable which connects between NIC and switch, and the standby NIC is changed to the online NIC.

The line monitoring method of four transmission paths is indicated below.

[Figure B.2 Line Monitoring of Multipath method (four communication paths)]

When the Multipath method is activated, a monitor frame is periodically transmitted from the online NIC to switch which is connected standby NIC, and the response is monitored. In order to clarify which devices is failure, if there is no response from the switch (4), like the switch (3), the switch (2), the switch (1), the candidate for the line monitoring will be brought close to online NIC in order, and will be monitored. The failure is detected by either the switch (1), the cable connected to it, or NIC, and the state after the communication path was changed is shown in "Figure B.2 Line Monitoring of Multipath method (four communication paths)." In this case, monitor frames are transmitted from the online NIC to both switch (1) and switch (4) simultaneously, and responses are monitored.

The communication path of "fail" state can be recovered as "standby" or "active" state by removing the cause of Link Down. In the failure monitoring of standby NICs, the link status of the driver that controls a standby NIC is monitored periodically.