gtpc1m0uTransmission Control Protocol/Internet Protocol

Storage Considerations

To calculate the number of bytes you will need for TCP/IP control block structures, you must consider:

SNAKEY Parameters

The following list shows the approximate number of bytes of storage allocated for TCP/IP control block structures for SNAKEY parameters:

Parameter
Approximate Number of Bytes

CLAWADP
303 220

CLAWFD
280

CLAWIP
64

Miscellaneous Control Block Structures

There are approximately 4 120 bytes allocated for additional TCP/IP control block structures whose size does not depend on the values of any of the three SNAKEY values described in this chapter.

Socket Thread Control Blocks

There are 32 bytes allocated for each socket thread control block. The number of socket thread control blocks allocated is equal to the total number of entry control blocks (ECBs) in the system.

Calculating the Approximate Total Number of TCP/IP Bytes

The following formula calculates the approximate total number of bytes required for the TCP/IP control block structures:

(303 220 × clawadp) + (280 × clawfd) + (64 × clawip) +
miscellaneous + (32 × ecbs) = the total number of bytes

where:

clawadp
is the value set for the CLAWADP parameter in the SNAKEY macro.

clawfd
is the value set for the CLAWFD parameter in the SNAKEY macro.

clawip
is the value set for the CLAWIP parameter in the SNAKEY macro.

miscellaneous
is 4120 bytes in block structures not associated with the SNAKEY macro.

ecbs
is the total number of ECBs in the system.

Example Calculating the Approximate Total Number of TCP/IP Bytes

Table 1 assumes values for the given SNAKEY parameters. Based on these values, the table shows the total number of bytes required for TCP/IP.

Table 1. Assumed TCP/IP Values

Parameter Approximate Number of Bytes for Each Value Value Used Total Number of Bytes for Each Parameter
CLAWADP 303 220 2 606 440
CLAWFD 280 4000 1 120 000
CLAWIP 64 3 192
ECBs 32 200 6 400
Miscellaneous 4 120 N/A 4 120
Total N/A N/A 1 737 152

The approximate total number of bytes allocated for the control block structures allocated by SNAKEY parameters, socket thread control blocks, and miscellaneous bytes required for TCP/IP support for this example is:

(303 220 × 2) + (280 × 4000) + (64 × 3)
+ (200 × 32) + 4120 = 1 737 752 total bytes