Managing Serviceguard 12th Edition, March 2006

Understanding Serviceguard Software Components
How the Network Manager Works
Chapter 3 105
During the transfer, IP packets will be lost, but TCP (Transmission
Control Protocol) will retransmit the packets. In the case of UDP (User
Datagram Protocol), the packets will not be retransmitted automatically
by the protocol. However, since UDP is an unreliable service, UDP
applications should be prepared to handle the case of lost network
packets and recover appropriately. Note that a local switchover is
supported only between two LANs of the same type. For example, a local
switchover between Ethernet and FDDI interfaces is not supported, but
a local switchover between 10BT Ethernet and 100BT Ethernet is
supported.
Figure 3-16 shows two nodes connected in one bridged net. LAN
segments 1 and 2 are connected by a hub.
Figure 3-16 Cluster Before Local Network Switching
Node 1 and Node 2 are communicating over LAN segment 2. LAN
segment 1 is a standby.
In Figure 3-17, we see what would happen if the LAN segment 2 network
interface card on Node 1 were to fail.