PeSIT SIT protocol: Start here

This book begin with this topic which provides an overview of the PeSIT protocol. The books is comprised of the following topics, which provide the information you need to configure the PeSIT protocol, and its variants, for Transfer CFT.

Topic Describes

Transfer parameters

The CFTPART parameters that must be defined to use the PeSIT protocol and transferred file characteristics.

PeSIT SIT examples

Details for an example, a file identified (SIT name), using the PeSIT SIT protocol.

Message characteristics

Additional information concerning PI codes and protocol errors when using the PeSIT SIT protocols.

PI codes

A table indicating the list of PI codes of PeSIT messages.

PGI codes

A table indicating the list of PGI codes of PeSIT messages.

Establishing a link

Details for a service item to establish a logical link between two PeSIT service users.

About the SIT profile

Basic features

The SIT profile, as a function of the level of the services required in exchanges between MSIT monitor and SIT workstation, corresponds to the basic PeSIT protocol. The definition of the SIT profile contains the fewest functional units.

The relative poorness of the SIT profile is due to its highly targeted application domain. This reflects the loss of a number of functions, at the ASIT application level. For example, as the compression of data transferred in the SIT network is not the responsibility of MSIT monitors, the SIT profile does not activate the PeSIT standard compression algorithms.

The SIT profile handles:

  • Send requests but not reception requests: only write transfers are supported
  • Concatenation of several transfers over the same connection
  • Synchronization points taken during transfer, as follows:
  • For each synchronization point there is a corresponding specific FPDU that the sender inserts between two data FPDUs. This FPDU (SYN) allows the receiver to acknowledge at the same time all the data received since the previous FPDU SYN.
  • In the protocol connection phase, PeSIT also allows two parties to dynamically negotiate the values of the parameters which control the definition of synchronization points and the acknowledgements during consecutive transfers
  • The resumption, from a previous synchronization point, of a transfer interrupted as a result of an incident or a temporary suspension

Specific features

The SIT profile also has many specific features in terms of both the values and the format of certain external parameters. These specific features stem directly from the architecture and operation of the SIT network.

These specific features are especially important in both the case of the parameters used to identify the files transferred, and or in the case of the parameters used to identify the parties (ie, ir, cte, ctr). This special naming and addressing is discussed further on in this sub-book.

  • Additionally, between the D version and the E version of PeSIT, the only profile whose definition remains unchanged is the SIT profile

The most recent specifications have, however, provided additional clarifications and are now considered as a reference.

  • PeSIT, in the SIT profile, is an unsymmetrical protocol. The result of this is that a ctb to workstation transfer does not follow the same protocol rules as a workstation to ctb transfer (the SIT stamp, in particular, is present in the workstation to ctb direction only)

Note that Transfer CFT is designed to be able to act as an MSIT but not as a workstation.

About Transfer CFT MSIT

In the SIT profile of the PeSIT protocol, Transfer CFT is an MSIT monitor, and is operational on a Processing Center site.

Functional architecture of SIT partners

Example of PeSIT SIT partners architecture with ASIT application

Transfer CFT parameter setting observes a particular syntax to designate the connected partners and the files exchanged.

Partner addressing

The SIT profile connects partners through installations:

  • Processing Centers, which are terminally connected logical partners:
  • CTE - Sender Processing Center
  • CTR - Receiver Processing Center
  • Logical installations hosted by physical computers, SIT stations routing the data flow. One station can host several installations

A distinction is made between Sender Installations, IE, directly connected to Sending Processing Centers, and Receiver Installations, IR, directly connected to Receiving Processing Centers.

The requester and server partner identifications are installation references formed by the:

  • Installation type: CTE, CTR, IE or IE
  • SIT installation number

A sending processing center will be coded as CTE00001, for example.

The four possible data flows are:

  • CTE to IE
  • IE to CTE
  • IR to CTR
  • CTR to IR

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