TS Supplement (Includes RFC-1006 Support)

Changes in the Transport Layer When Using RFC-1006

Introduction to RFC-1006

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is performed on the server (by calling Accept_nw2 socket routine). This will result in

an N-CONNECTION.CONFIRMATION event on the transport service client.

In OSI/TS, a TS server does not listen (perform a PASSIVE open, or perform an N-

ATTACH action) until the called TS-user performs a T-ATTACH action.

Data Transfer

The procedures used during data transfer are identical to those presented in ISO 8073,

with one exception: expedited data may be supported (if the use of it was negotiated

during connection establishment) by sending an ED-TPDU. The ED-TPDU is sent on

the same TCP/IP connection as are all of the other TPDUs.

In the Tandem RFC-1006 implementation, each received ED-TPDU is not

acknowledged with an Expedited Acknowledge (EA) TPDU. (An EA-TPDU is an

invalid TPDU in RFC 1006 OSI transport protocol class 0 service.) In addition, an ED-

TPDU with a zero-length data field is treated as a protocol error.

To perform an N-DATA.REQUEST action, the sending transport service peer

constructs the desired DT-TPDU transport packet and uses the TCP Send Data service

primitive. The receiving transport service peer reads a DT-TPDU transport packet

using the TCP Read Data service primitive. Note that TCP does not trigger an

N-DATA.INDICATION action (does not inform receiving transport service peer that

data is ready to read).

In OS/TS, a receiving TS-peer does not read data until the receiving TS-user informs

the TS-peer to read.

Connection Release

To perform an N-DISCONNECT.REQUEST action, the transport service peer simply

closes the TCP connection, using the TCP Close service primitive. The TCP process

does not trigger an N-DISCONNECT.INDICATION action (does not inform transport

service peer that the TCP connection is closed). When the TCP connection is closed,

the only signal that is received is the completion of a RECV_NW call with a length of

zero (0).

Connection Reset

OSI/TS does not perform N-RESET.REQUEST actions on RFC-1006 transport

connections, but TCP connections can be reset. When a TCP connection is reset, the

only signal that is received by a transport service peer is an error code ECONNRESET,

returned on a RECV_NW or SEND_NW socket call. This is a type of

N-RESET.INDICATION primitive. The transport service peer just needs to call

CLOSE to close the socket.