Current call setup mode. The 1xEV-DO system supports packet
data connections to a public or private data network using
either mobile IP or simple IP protocol. For simple IP
protocol, moving from the coverage area of one PDSN to another
PDSN constitutes a change in packet data session. For mobile
IP protocol, a packet data session can span several PDSNs as
long as the user continuously maintains mobility bindings at
the Home Agent (the IP address is persistent). The modes are:
unknown(1) - mode is unknown
simpleIpOnly(2) - simple IP only
mobileIpPreferWithSipFallback(3) - prefer mobile IP with
simple IP as fallback mode
mobileIpOnly(4) - mobile IP only