Expand Configuration and Management Manual (G06.24+)

Subsystem Description
Expand Configuration and Management Manual—523347-008
18-55
Expand-over-IP Connection Establishment
that provides a mechanism for identifying the ultimate destination in a host, such as an
application program or other high-level process.
Each NonStop TCP/IP process appears to an IP network as a separate host and is
associated with a separate IP address. An IP address is a 4-octet (32-bit) numeric
value identifying a particular network (network address portion) and a local host on that
network (local address portion). A NonStop TCP/IP process can be associated with
more than one IP address. There can also be more than one NonStop TCP/IP process
on the system at any one time; each process acts as a separate NonStop TCP/IP host.
Parallel Library TCP/IP and NonStop TCP/IPv6 provide a feature called single IP
which allows a single TCPSAM or TCP6SAM process to act as a single host for all 16
processors. NonStop TCP/IPv6 also provides the option of using IP version 6 (IPv6)
communications. IPv6 provides several new networking features and a longer, 128-bit
IP address.
Both TCP and UDP use a 16-bit port number to select a socket on the host. TCP and
UDP add to IP the capability of having several simultaneous sessions with a given
host. Multiple sessions are accommodated by specifying a port number, which
identifies the communications path, along with the IP address. Each end of the
communications path is assigned a port number for that session.
Expand-over-IP line-handler processes perform addressing by specifying a unique
combination of a destination IP address, destination port number, source IP address,
and source port number.
Expand-over-IP Connection Establishment
When the system is started up, the Expand-over-IP line-handler process waits for the
NonStop TCP/IP, TCPSAM, or TCP6SAM process (with which it is associated) and the
QIO Monitor process (QIOMON) to start. These processes must be running before
Expand-over-IP lines can be started. Next, the Expand-over-IP line-handler process
binds to its associated NonStop TCP/IP, TCPSAM, or TCP6SAM process.
Once the Expand-over-IP line-handler process has successfully bound to the NonStop
TCP/IP, TCPSAM, or TCP6SAM process, it attempts to establish a connection to the
remote Expand-over-IP line-handler process. There are two ways the Expand-over-IP
line-handler process can attempt to establish a connection: active connect or passive
connect.
The default connect method is active connect. You can cause the Expand-over-IP line-
handler process to use the active connect method by specifying the
CONNECTTYPE_ACTIVEANDPASSIVE modifier.
Note. The Expand End-to-End protocol already provides the sequencing, error-recovery, and
congestion control functions that a reliable stream transport service such as TCP/IP provides,
making it unnecessary for the Expand-to-IP interface to duplicate these functions.