paCmdIpFrag_t Struct Reference
[PA LLD Data Structures]

IP fragmentation information. More...

#include <pa.h>

Data Fields

uint16_t ipOffset
uint16_t mtuSize

Detailed Description

IP fragmentation information.

paCmdIpFrag_t is used to create the IPv4 fragment command. The IP fragment command is used to instruct the PASS to perform IPv4 fragmentation operation. This operation can be applied to both inner IP prior to IPSEC encapsulation and outer IP after IPSEC encapsulation. This command should go with a next route command which provides the destination information prior to the fragmentation operation.

For the inner IP fragmentation, follow the following procedure:

For the outer IP fragmentation, the overall operation is stated below:

Note:
the next route command is required for step 2
The IP fragment command can not be combined with some other tx commands such as checksum and CRC commands since those commands may require the PASS operation across multiple fragments. The workaround is to break the tx commands into two groups. The first group consists of the checksum, CRC, other commands and a next route command which routes the packet back to the same PDSP to execute the second command group which consists of the IP fragment command and the next route command which points to the final destination.

The IP fragment command can be combined with a single blind patch command to support the IPSEC AH use case in which the SASS passes the IPSEC AH packet with the blind patch command to the PASS so that the autentication tag can be inserted into the AH header. The recommended order of the tx commands is as the followings:

The IP fragment command can be also combined with up to two message length patching commands to support the message length field updating for each IP fragment. This operation is required for certain L2 header which contains a length field such as 802.3 and PPPoE. The order of tx command is as the followings:


Field Documentation

Offset to the IP header.

Size of the maximum transmission unit (>= 68)


The documentation for this struct was generated from the following file:

Copyright 2012, Texas Instruments Incorporated