gtpc1m1p | Transmission Control Protocol/Internet Protocol |
The IP message table (IPMT) contains the following:
The IPMT resides in main storage and consists of a pool of 4-KB entries that are assigned dynamically on demand.
Output messages reside in the send buffer of a socket. Input messages reside in the receive buffer of a socket. The IPMT is the physical storage used by send and receive buffers. IPMT entries are not preallocated to send and receive buffers. Instead, IPMT entries are assigned only when needed. For example, assume the receive buffer size for a socket is 100 KB and there are no input messages queued for this socket. For this, there are no IPMT entries being used for input messages. Next, assume a 500-byte message arrives for this socket. An IPMT entry will be assigned to the receive buffer of the socket and the 500-byte message will be copied into that entry. When the application reads the 500-byte message, the IPMT entry will be returned to the system.
The IPMTSIZE parameter on the SNAKEY macro in CTK2 defines the number of 4-KB entries in the IPMT. The IPMT is usually the TCP/IP native stack support table that requires the most main storage. The following factors must be taken into consideration when determining the size of the IPMT: