Topology Services defaults and limitations

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The maximum node number allowed is 2047. The maximum number of networks it can monitor is 48.

Topology Services is meant to be sensitive to network response and this sensitivity is tunable. However, other conditions can degrade the ability of Topology Services to accurately report on adapter or node membership. One such condition is the failure to schedule the daemon process in a timely manner. This can cause daemons to be late in sending their heartbeats by a significant amount. This can happen because an interrupt rate is too high, the rate of paging activity is too high, or there are other problems. If the daemon is prevented from running for enough time, the node might not be able to send out heartbeat messages and will be considered, incorrectly, to be down by other peer daemons.

Since Topology Services is a real time process, do not intentionally subvert its use of the CPU because you can cause false indications.

On AIX® nodes, Topology Services sets all four of the following options to 1 so that the reliable message feature, which utilizes IP source routing, will continue to work:
  • ipsrcroutesend (default is 1)
  • ipsrcrouterecv (default is 0)
  • ipsrcrouteforward (default is 1)
  • nonlocsrcroute (default is 0)
Disabling any of these network options can prevent the reliable message feature from working properly.

ATTENTION - READ THIS FIRST

The network options to enable IP source routing are set to their default values for security reasons. Since changing them may cause the node to be vulnerable to network attack, system administrators are advised to use other methods to protect the cluster from network attack.

Topology Services requires the IP source routing feature to deliver its data packets when the networks are broken into several network partitions. The network options must be set correctly to enable the IP source routing. On Linux® Systems, the Topology Services startup command will set the following options:
IP forward: enable
echo 1 > /proc/sys/net/ipv4/ip_forward
Accept Source Routing: enable
echo 1 > /proc/sys/net/ipv4/conf/all/accept_source_route

echo 1 > /proc/sys/net/ipv4/conf/interface/accept_source_route

RP Filter: disable
echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter

echo 0 > /proc/sys/net/ipv4/conf/interface/rp_filter