Toshihiko Kato

Design of Protocol Monitor Emulating Behaviors of TCP/IP Protocols

Recently, the TCP/IP protocols are widely used and it is mentioned that, in some cases, throughput is limited due to problems such as network congestion. To solve such problems, the details of communication need to be examined. In order to support these examinations, we are developing an ‘intelligent’ protocol monitor which can estimate what communication has taken place by emulating the behaviors of the TCP protocol entities in a pair of communicating computers. This paper describes the overview of the monitor and the detailed design of the TCP behavior emulation function for both the state transition based behaviors and the internal procedures for the flow control, such as the slow start algorithm.

Interoperability Testing System of TCP/IP Based Communication Systems in Operational Environment

Recently, TCP/IP protocols are widely used. Here, although the protocols are realized in operating systems and users of communication systems pay no attention to their detail, some system errors are actually reported. Since those errors occur only in specific communication situations, the interoperability testing by watching communication by a testing system is appropriate to detect them. This interoperability testing has the following requirements. Firstly, since the system that includes system errors is not unidentified, the testing system needs to check all communication systems attached to a network. Secondly, for the similar reason, all protocols in the TCP/IP protocol stack need to be checked. Thirdly, the testing system needs to discriminate operational failures, such as server down and mis-configuration of parameters in clients, from system errors, when it detects any problems in the communication. Based on these considerations, we have designed an interoperability testing system of TCP/IP based communication systems applied in an operational environment. This paper describes the detailed design of our testing system and the testing algorithm for DHCP (Dynamic Host Configuration Protocol), for which some system errors are reported.

High speed TCP/IP experiment over international ATM test bed

AT&T, KDD and NTT conducted a joint ATM trial called Multimedia Application Project (MAP) for the purpose of testing and validating network-based broadband multimedia applications and services between US and Japan. Although the Internet based network is promising for broadband multimedia communications, there is a performance problem that TCP is the throughput bottleneck in an international ATM network with large propagation delay. In MAP, the high speed TCP/IP experiment was jointly performed by the three companies with the leadership of KDD, for the purpose of validating the high speed TCP/IP infrastructure using TCP gateway proposed by KDD. In this infrastructure, a pair of TCP gateways are introduced in international ATM networks, and they improve the TCP throughput by introducing a link-by-link flow control and a sufficient window size between gateways, without any modifications to end terminals.

Design of Intelligent OSI Protocol Monitor

As the OSI protocols come to be widely adopted in various communication systems, the testing of OSI protocol implementations becomes important. In this testing, the interoperability testing is performed to examine the interconnectability which cannot be checked in the conformance testing. In this paper, we propose the Intelligent OSI Protocol Monitor which observes PDUs (Protocol Data Units) exchanged between OSI system and analyzes the protocol behaviors as well as the PDU format according to the protocols of OSI 7 layers. This monitor is effectively used to observe the actual communication for a long period and to detect protocol errors which cannot be detected by the conformance testing. This paper describes the detailed design of the Intelligent OSI Protocol Monitor and shows how it works for actual OSI protocols.

OSI protocol testing system based on user friendly test scenario specification functions

As the OSI protocols come to be widely adopted in various communication systems, the testing of OSI protocol implementations becomes important. In this paper, we propose the OSI protocol testing system with user friendly test scenario specification functions aiming to support both the state transition oriented testing and the parameter oriented testing for the Transport through Application layer protocols. Our system introduces the separate tools with friendly human interface for specifying the test scenarios, for the test execution and for analyzing the test results. This paper describes the function and implementation of our system and shows its usefulness compared with the conventional testing system based on formal specification language.

A TCP Test System Specifying only Exceptional Packet Sequences

Although TCP is widely used in Internet, new specifications are still proposed and implemented. In the circumstance above, it is highly possible that some errors are detected on the communication between new and old implementations. Several test tools were developed so far. However, they do not have enough function to customize test sequence or need significant effort to specify the sequence. We developed a TCP test system which specifies only exceptional packet sequence in the test scenario. The system performs exceptional packet sequence only when the condition specified in the test scenario is satisfied. Otherwise, it performs ordinary TCP behavior. The system is implemented by modifying TCP module of NetBSD with SACK code developed by Pittsburgh Supercomputing Center. We also evaluated SACK implementation as an example of recent specification using the test system.

Intelligent Protocol Analyzer for WWW Server Accesses with Exception Handling Function

Recently, the TCP/IP protocols are widely used and it is mentioned that there are problems such that the throughput is limited due to protocol procedures such as retransmission and congestion control of TCP. In order to analyze these problems, we have developed an “intelligent” protocol analyzer which can estimate what communication has taken place by emulating the behaviors of the IP, TCP and HTTP protocol entities, which are used for WWW server access communications. This analyzer also supports the handling of exceptional situations such as monitoring errors and network misbehaviors. This paper describes the details of the emulation functions of HTTP and the exception handing functions, and shows some results of applying the analyzer to actual WWW server accesses.