TS Supplement (Includes RFC-1006 Support)

Changes in the Transport Layer When Using RFC-1006

Introduction to RFC-1006

1–16 107751 Tandem Computers Incorporated

Transport Service User

Data

When TCP/IP is the NSP process, user data is exchanged during connection

establishment. Up to 32 octets of transport service user data can be exchanged during

connection establishment in CR-TPDUs and CC-TPDUs.

If you use a CONTROL 17 or CONTROL 11 procedure to request or respond to

connection establishment, user data cannot be sent in the CR- and CC-TPDUs. If you

use a WRITEREAD procedure to request or respond to connection establishment, user

data can be sent in the CR- and CC-TPDUs.

When X25AM is the NSP process, user data is not exchanged during connection

establishment for OSI transport protocol class 0.

Transport Expedited Data When TCP/IP is the NSP process, OSI/TS supports transport expedited data transfer

service for OSI transport protocol class 0. OSI/TS can use network expedited data

transfer service (TCP/IP out-of-band data facility) for Expedited Data (ED) TPDUs.

The Tandem RFC-1006 implementation defines the default for the EXPEDITED

configuration attribute as OFF.

When X25AM or TLAM is the NSP, OSI/TS supports ED-TPDU transfer service for

classes OSI transport classes 1, 2, 3, and 4 only.

Larger TPDU Size When TCP/IP is the NSP, OSI/TS supports TPDU sizes up to 65531 octets. Use of a

larger TPDU can improve throughout due to decreased numbers of interprocess

communication (IPC) messages.

When X25AM or TLAM is the NSP, OSI/TS supports a TPDU size up to 8192 octets for

OSI transport classes 1, 2, 3, and 4 and supports up to 2048 octets for class 0.

TPDU and Transport Packet

Structure

Table 1-2 lists the six TPDUs used by OSI/TS when it is using RFC-1006.

Table 1-2. TPDUs Used by RFC-1006

TPDU Function

CR-TPDU During connection establishment, used to request a transport connection

and to exchange user data

CC-TPDU During connection establishment, used to confirm a CR-TPDU and to

exchange user data

DT-TPDU During data transfer, used to transfer user data

ED-TPDU * During data transfer, used to transfer expedited user data

DR-TPDU During connection release, used to request a connection release

ER-TPDU Used to convey error information

*Normally the ED-TPDU is not provided for OSI transport protocol class 0, but it is included when

using RFC-1006.