RFC 938 (rfc938) - Page 1 of 16
Internet Reliable Transaction Protocol functional and interface specification
Alternative Format: Original Text Document
Network Working Group Trudy Miller
Request for Comments: 938 ACC
February 1985
Internet Reliable Transaction Protocol
Functional and Interface Specification
STATUS OF THIS MEMO
This RFC is being distributed to members of the DARPA research
community in order to solicit their reactions to the proposals
contained in it. While the issues discussed may not be directly
relevant to the research problems of the DARPA community, they may be
interesting to a number of researchers and implementors. This RFC
suggests a proposed protocol for the ARPA-Internet community, and
requests discussion and suggestions for improvements. Distribution
of this memo is unlimited.
ABSTRACT
The Internet Reliable Transaction Protocol (IRTP) is a transport
level host to host protocol designed for an internet environment. It
provides reliable, sequenced delivery of packets of data between
hosts and multiplexes/demultiplexes streams of packets from/to user
processes representing ports. It is simple to implement, with a
minimum of connection management, at the possible expense of
efficiency.
Miller [Page i]
RFC 938 February 1985
Internet Reliable Transaction Protocol
TABLE OF CONTENTS
INTRODUCTION
1.1 Purpose ......................................... 1
1.2 Underlying Mechanisms ........................... 1
1.3 Relationship to Other Protocols ................. 2
IRTP HEADERS
2.1 Header Format ................................... 3
2.2 Packet Type ..................................... 3
2.3 Port Number ..................................... 3
2.4 Sequence Number ................................. 4
2.5 Length .......................................... 4
2.6 Checksum ........................................ 4
INTERFACES
3.1 User Services Provided By IRTP .................. 5
3.2 IP Services Expected by IRTP .................... 5
MODEL OF OPERATION
4.1 State Variables ................................. 6
4.2 IRTP Initialization ............................. 7
4.3 Host-to-Host Synchronization .................... 7
4.3.1 Response to SYNCH Packets ..................... 7
4.3.2 Response to SYNCH ACK Packet .................. 8
4.4 Transmitting Data ............................... 8
4.4.1 Receiving Data From Using Processes ........... 8
4.4.2 Packet Retransmission ......................... 10
4.5 Receiving Data .................................. 10
4.5.1 Receive and Acknowledgment Windows ............ 11
4.5.2 Invalid Packets ............................... 12
4.5.3 Sequence Numbers Within Acknowledge Window .... 12
4.5.4 Sequence Numbers Within the Receive Window .... 12
4.5.5 Forwarding Data to Using Processes ............ 13
IMPLEMENTATION ISSUES
5.1 Retransmission Strategies ....................... 14
5.2 Pinging ......................................... 14
5.3 Deleting Connection Tables ...................... 16
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RFC 938 February 1985
Internet Reliable Transaction Protocol
LIST OF FIGURES
Figure 1-1 Relationship of IRTP to Other Protocols . 2
Figure 2-1 IRTP Header Format ...................... 3
Figure 4-1 SYNCH Packet Format ..................... 8
Figure 4-2 SYNCH ACK Packet Format ................. 8
Figure 4-3 DATA Packet Format ...................... 9
Figure 4-4 DATA ACK Packet Format .................. 11
Figure 4-5 PORT NAK Packet Format .................. 11
ABBREVIATIONS
ICMP Internet Control Message Protocol
IP Internet Protocol
IRTP Internet Reliable Transaction Protocol
RDP Reliable Data Protocol
TCP Transmission Control Protocol
UDP User Datagram Protocol
Miller [Page iii]
RFC 938 February 1985
Internet Reliable Transaction Protocol
CHAPTER 1 - INTRODUCTION
The Internet Reliable Transaction Protocol (IRTP) is a full duplex,
transaction oriented, host to host protocol which provides reliable
sequenced delivery of packets of data, called transaction packets.
Note: throughout this document the terms host and internet address
are used interchangeably.
1.1 Purpose
The IRTP was designed for an environment in which one host will
have to maintain reliable communication with many other hosts. It
is assumed that there is a (relatively) sporadic flow of
information with each destination host, however information flow
may be initiated at any time at either end of the connection. The
nature of the information is in the form of transactions, i.e.
small, self contained messages. There may be times at which one
host will want to communicate essentially the same information to
all of its known destinations as rapidly as possible.
In effect, the IRTP defines a constant underlying connection
between two hosts. This connection is not established and broken
down, rather it can be resynchronized with minimal loss of data
whenever one of the hosts has been rebooted.
Due to the lack of connection management, it is desirable that all
IRTP processes keep static information about all possible remote
hosts. However, the IRTP has been designed such that minimal state
information needs to be associated with each host to host pair,
thereby allowing one host to communicate with many remote hosts.
The IRTP is more complex than UDP in that it provides reliable,
sequenced delivery of packets, but it is less complex than TCP in
that sequencing is done on a packet by packet (rather than
character stream) basis, and there is only one connection defined
between any two internet addresses (that is, it is not a process
to process protocol.)
1.2 Underlying Mechanisms
The IRTP uses retransmission and acknowledgments to guarantee
delivery. Checksums are used to guarantee data integrity and to
protect against misrouting. There is a host to host
synchronization mechanism and packet sequencing to provide
duplicate detection and ordered delivery to the user process. A
simple mechanism allows IRTP to multiplex and demultiplex streams
Miller
