EDI GUIDELINE
GENERAL SECTION
6
COMMUNICATIONS
Communication
This section is concerned with computer to computer communication and contains information on
protocols, communication options, and network interconnects.
6.1
General Introduction
There are two parts to EDI, the message standards and the communication option for transmitting
those standards. This section provides an overview of the communication options available to a
company planning to implement EDI. Its purpose is to highlight the areas in which key data
communication design decisions must be made. There is no single or preferred solution in this
decision making process. Each company must determine the proper approach based on current
and projected transaction volume and level of investment.
When a company plans to implement EDI, consideration should be given as to how the data will
be communicated between trading partners, either physical or electronic means. Physical
communications include the use of magnetic tapes/cartridges, floppy disks or CD’s. Electronic
communications employs the use of public or private telecommunications lines
When electronic communications are selected, all parties need to identify, negotiate, and select
the communication transfer mode. Issues to be addressed include the sending and receiving
location, protocol and transmission parameters. Both long and short term EDI communications
strategies should be analyzed to determine the current and future business and/or industry
environment with respect to their EDI trading relationships. Criteria to be considered when
determining the communication mode of data transfer include the following:

Distance of transport

Number of destinations

Costs required
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Delivery time frame
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Frequency of transport

Security

Volume of transactions
The exchange of EDI data can be accomplished using various methods, such as: dedicated or
switched networks, TCP/IP, U.S. Mail or courier service, and more recently, the Internet. Each
exchange method should be analyzed to determine if the approach meets the company’s and
trading partners' communication needs.
No matter, which approach, is selected a contingency plan should be formulated to address the
possible event of a communication failure.
Issues to be considered are backup procedures to address system failures, transmission error
recovery including the establishment of a maximum number of retransmit attempts, security,
network response time, and error reporting.
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
COMMUNICATIONS
References:
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ASC X12 Publications



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IBM Publication References



"An Introduction to Electronic Data Interchange"
"Transfer of ASC X12 Data Using Asynchronous or Binary Synchronous
Communication Protocol"
"EDI Asynchronous Guideline"
Binary Synchronous Communications Order #GA2730042
IBM 3780 Data Communications Terminal Order #GA2720633
Ordering and Billing (OBF) Publication References

Lower Layer Protocol Specifications for EDI over TCP/IP (This document
describes in detail the lower layer protocol specifications of doing EDI over
TCP/IP)
6.1.1 EDI Communication Network Alternatives
Following are three EDI data communication network alternatives:

Dedicated networks

Switched networks

Network value added services
Dedicated networks incorporate point to point circuits that permanently connect two sites.
Switched networks employ circuit switching, message switching, or packet switching technology.
In each, connections between sites are made by one or more switches and are disconnected after
the transmission is over.
Network value added services are features provided by telecommunication networks in addition to
transporting data. Common examples include electronic mailboxes, storage, speed and code
conversion, compliance checking, and translation. Security is also provided as a value added
service. Service providers usually employ switched network technology.
An organization's own specific EDI transmission requirements, including current and future
systems, will determine the appropriate mix of these alternatives. A communication survey of the
proposed trading partners should be conducted in the early stages of planning to determine the
software/hardware environment.
Questions that need to be answered:

What type of computer will be used to process EDI messages?

What operating system software is the computer running?

What type of communication equipment will be used to send and receive EDI messages?
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
What translator will be used to convert application data into an EDI format?

The throughput for each EDI transaction?
6.1.2 Data Communication Function
The ASC X12 publication, "Guideline: Transfer of ASC X12 Data Using Asynchronous or
Binary/Synchronous Communication Protocol" provides guidance on the technical procedures
needed to ensure accurate data transfers between EDI trading partners. The guideline provides a
definition of the data communication function and discusses the critical elements of data
communication planning which include:

Identification of intended communication partners

Establishment of authority to communicate
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Agreement of privacy mechanisms
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Authentication of communication partners

Determination of the adequacy of resources

Determination of acceptable quality of service
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Synchronization of cooperating applications

Selection of dialogue description

Agreement of responsibility for error recovery

Agreement of procedures for control of data integrity

Identification of constraints on data syntax/structure
The guideline also references basic requirements concerning the trading partner's EDI
communication system.
These requirements are:

Sufficient data storage for the retention of transmitted and received EDI data, trading
partner authentication information, and status of data transfers.

Ability to provide the current status of data transfers.

Reliable storage devices provide data backup and restoration capability.
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6.2
COMMUNICATIONS
Protocols
Protocol is the collective term for the rules that govern communication at a given layer in network
architecture. They are important because in each layer, in any communication system, a set of
rules must be agreed to and followed in order for communication to be successful.
6.2.1 EDI Data Transfer Protocol
The ASC X12 publication, "Guideline "Transfer of ASC X12 Data Using Asynchronous or Binary
Synchronous Communication Protocol" defines the basic requirements to be addressed by EDI
trading partners. They are communication compatibility, security, and data integrity.
Communication compatibility refers to:

Electrical signaling




Line control protocol








between communications software, such as asynchronous, binary
synchronous, and other protocols
call establishment
data blocking and organization
acknowledgement and signaling for handshaking and error control
line turnaround procedures
character synchronization
escape interrupt disconnect
Data transfer protocol


signaling between communication hardware, modem communications, and
channel modem
modem types
transmission speed compatibility
compatible EDI data transfer programs and techniques for managing
data transfer
Security issues to be considered:



EDI data going only to the intended trading partner
control over access to communication and business systems
identification and authorization of trading partners
Data transfer process integrity refers to the actions taken to prevent problems. An objective of the
EDI communication system is to provide a high degree of data process integrity in order to:

Minimize potential loss of data by providing intermediate safe storage, interchange
authorization, retransmission approval, mutual results commitment

Minimize the potential for data duplication by providing temporary data suspension

Minimize the potential for situations that require human intervention by providing status
retention and transfer restart capabilities. Error detecting protocols should be considered
as the minimum communication requirement for EDI.
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6.2.2 Transmission Protocols
Data link protocols fall into two major categories, character oriented and bit oriented.
A character-oriented protocol that uses a particular code set for transmission with some of the
characters in the code set reserved for control functions. Asynchronous and binary synchronous
protocols are examples of this protocol.
Asynchronous transmission is defined as a transmission that is synchronized by the sending and
receiving data transmission equipment (DTE) before each character is sent. Each character has
a start and stop bit to indicate beginning and end of each character. The start and stop bits are
the mechanisms by which synchronization is established. Typical asynchronous communications
accommodated by microcomputers transmitted at a baud rate ranging between 300-4800 bits per
second (BPS) or higher. See ASC X12 draft publication: "EDI Asynchronous Guideline".
Binary-synchronous transmission is different from asynchronous in that bit synchronization is
established for a much longer duration, usually for the time it takes to transmit several thousand
bits. This results in less transmission overhead but requires more complex circuitry. Typical
binary synchronous communication is supported by a mainframe or communications front-end
processor transmitted at a baud rate ranging between 2400-9600 BPS or higher. See ASC X12
publication: "Transfer of ASC X12 Data Using Asynchronous or Binary Synchronous
communication Protocol".
A bit-oriented protocol is independent of any particular code set, and no character codes are
reserved for control functions. High level data link control (HDLC) and advanced data
communication control procedures (ADCCP) are examples of this protocol. The major advantage
is in speed and standardization.
6.3
Point-to-point (Dedicated Network)
Point-to-point circuits connect users on dedicated networks, typically through leased lines, private
networks and dial-up. These dedicated facilities are used when the need to transmit EDI
transactions between the two ends is steady and continuous. Since the users are paying for the
link regardless of the number of transmissions, its usage must be high for it to be economical.
See the figure below.
Company A’s
Micro
Computer
Point to Point
Company B’s
Mainframe
Computer
Selection of this alternative requires an in-house staff capable of managing the network. Items
that must be addressed:

Network availability
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6.4
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Service level
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Network response time

Network communications
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Communication speed
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Transmission mode
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Modem capability

Line protocol

Cost
COMMUNICATIONS
Third Party Services
Third party services are those employing switched network technology and providing value added
services.
Switched networks with connect and disconnect circuits are required to transmit data. The three
common methods are:

Circuit switching

Message switching

Packet switching
Circuit switching is used in public telephone systems. A circuit is dedicated between the source
and destination for the duration of the transmission. The sender and receiver must be available at
the same time. Message switch networks package the data in messages and pass the messages
from switch to switch. The sender and receiver do not have to be available at the same time,
since the message is stored at each intermediate step. For this reason, message switched
networks are also referred to as store and forward networks.
Packet switching is similar to message switching, but it divides the data into smaller, equal-sized
pieces called packets. The time it takes to move data through the network is less, since large
messages don't have to be stored at each intermediate switch. The reduced delay, over message
switching, allows the two users to carry on a dialogue, referred to as an interactive process. In
addition, the reduced delay aids transaction processing by moving the transactions to their
destination quickly.
The advantage of packet switching versus circuit switching is in making efficient use of the data
lines. Each packet carries a destination address, so packets from multiple sources heading to
different destinations can be transmitted down the same data line if it is desirable.
The above facilities and services may be obtained from commercial networks (third party service)
rather than developed in-house. The commercial networks provide the network management and
knowledgeable staff to support communication requirements. Commercial networks now offer
more than moving data from one site to another. Services provided include mailbox service, data
storage, speed and format conversion, or translation.
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A communication survey will help companies choose the services needed. If a commercial
network alternative is selected, the network will provide technical instructions required for access
to the network. The same items listed in Section 6.3 must be addressed.
Typically, not all companies have the communication facilities to accommodate the multiple
communication protocols in use by their potential trading partners. Third party service providers
eliminate the need for a company to invest heavily in communication hardware, software, and
personnel. A third party service provider allows the convenience of a single data transfer link to
multiple trading partners independent of operating schedules, protocol conversion, hardware
interface, and conversion requirements.
When selecting a third party service provider, a company should evaluate the service capabilities
and performance offered. Issues to consider:

Speed of delivery mode

Outdial capabilities (e.g., autodial, scheduled)

Data integrity

Reliability

Job queuing options

Interconnect capabilities

Tracking and control reporting (audit, historical, and exception reporting)

Costs
Before data transfer begins with a third party service, communications should be mutually defined
and agreed upon. The use of third party communications should be transparent to trading
partners.
Usually each trading partner pays for the EDI services it received. Costs associated with the use
of a third party service include:
6.5

Start up charges

Monthly mailbox fee

Connect charge

Data storage

Network interconnect

Character charges

Reports
Network Interconnects
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When multiple commercial networks are needed to satisfy EDI requirements, an additional level of
complexity is added to communication solution. It is important that each network representative be
included in the planning process. Agreement must be reached on the items listed in Section 6.3.
Most EDI third party service providers’ offer a network interconnection capability. This capability
allows one, third party network to communicate with another. The connection is transparent to the
EDI trading partners. Network interconnects should be defined by all parties involved.
The interconnection service eliminates the need for a company to have mailboxes on multiple
third party service networks. There is an additional charge for the service, and thus must be
weighed against the cost of establishing additional mailboxes on other networks.
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