H3C Technologies H3C MSR 5600 - Manual (Page 13)

6
• Use temporary TCP connection mode for POS applications on Router A.
TPDU
Transport Protocol Data Unit (TPDU) is a field in a POS packet. A TPDU header is five bytes in length and
includes the following options:
• ID—One byte. It identifies the TPDU type. Typically, the correct packet type is 0x60. The incorrect
packet type is 0x68.
• Destination Address—Two bytes, also called the Network International Identifier (NII). It indicates
the destination address of the packet. Typically, the address is assigned by the transaction center to
identify the FEP of a bank.
• Originator Address—Two bytes. It identifies the POS terminal device.
For the reply packet of a POS packet, the originator address and destination address in the TPDU header
are reversed.
TPDU address change policy
Before the router forwards a packet from a POS terminal that uses TCP or dial-up access mode to an FEP,
it changes an address in the TPDU field to a cookie. Upon receiving a response from the FEP, the router
forwards the response to the corresponding POS terminal according to the cookie in the response.
FEPs require either the TPDU header's originator or destination address to change. Determine the TPDU
address change policy according to the requirements of FEPs.
Router Operation modes
The router may operate in transparent or nontransparent mode.
Transparent mode
In transparent mode, a POS terminal template directly forwards a packet received from a POS terminal
to a specific POS application template without checking the packet format. The router then creates a
dedicated TCP connection for the POS terminal in the POS application template.
POS terminals might send out packets that do not follow the TPDU format. You must use transparent mode
to transmit this type of packets. Otherwise, the packets are discarded.
The transparent mode does not support the flow connection mode between a POS application template
and an FEP.
The transparent mode supports FEP backup. For more information, see "
FEP backup ."
Nontransparent mode
In nontransparent mode, the router checks the format of each packet received from a POS terminal. If a
packet does not follow the TPDU format, the router discards the packet. If a packet is valid, the router uses
a POS application template based on the originator and destination addresses in the TPDU header, and
sends the packet to an FEP according to the application template.
In nontransparent mode, the router can use the same TCP connection for multiple POS terminals to
communicate with the FEP.