Implementation guide for the ISO Transport Protocol

Abstract

It is assumed that the reader is familiar with both the formal description technique, Estelle [ISO85a], and the transport protocol as described in IS 8073 [ISO84a] and in N3756 [ISO85b]. 1.1General interpretation guide.The development of the formal description of the ISO Transport Protocol was guided by the three following assumptions. A generality principleThe formal description is intended to express all of the behavior that any implementation is to demonstrate, while not being bound to the way that any particular implementation would realize that behavior within its operating context. Preservation of the deliberate nondeterminism of IS 8073The text description in the IS 8073 contains deliberate expressions of nondeterminism and indeterminism in the behavior of the transport protocol for the sake of flexibility in application.(Nondeterminism in this context means that the order of execution for a set of actions that can be taken is not specified. Indeterminism means that the execution of a given action cannot be predicted on the basis of system state or the executions of other actions.)

WTRP—Wireless Token Ring Protocol

“…WTRP is inspired by the IEEE 802.4 token bus protocol, which in turn was motivated by applications in factory automation, with requirements of bounded latency and robustness against multiple node failures [18], [22]. WTRP combines these features of bounded latency and robustness with the more versatile ad hoc wireless networks.…”

Improving the efficiency of the OSI checksum calculation

“…The checksum chosen for the first round of these international standards ( [IS86], [IS87], for example) was first proposed by John Fletcher [Fl82] as a way of providing the same order of protection as the more computationally expensive CRC algorithm. It has some interesting error detection properties, but is still somewhat expensive to compute, and has a decided impact on the total throughput of these protocols [Mc87]. Thus, even a modest improvement of five to ten percent in the speed of checksum computation conceivably could translate to a four to eight percent increase in transport throughput.…”

“…The OSI implementation given in [Mc87] (no unrolling, using ediv, aob, etc.) Each of these routines includes the mechanism (and consequent overhead) to process packets buffered in a segmented fashion.…”