Showing papers on "Transmission delay published in 1974"

A Protocol for Packet Network Intercommunication

Abstract: A protocol that supports the sharing of resources that exist in different packet switching networks is presented. The protocol provides for variation in individual network packet sizes, transmission failures, sequencing, flow control, end-to-end error checking, and the creation and destruction of logical process-to-process connections. Some implementation issues are considered, and problems such as internetwork routing, accounting, and timeouts are exposed.

The stability problem of broadcast packet switching computer networks

Abstract: Certain computer networks have been implemented using a radio broadcast frequency over which a large set of terminals are allowed to transmit packets of bits; one such example is the ALOHA computer network [1]. In such systems, a basic problem is that of the blocking of terminals whose transmission of a packet has overlapped in time with transmission by some other terminal. In this paper we consider a "slotted ALOHA" packet transmission scheme with an infinite set of terminals each transmitting at an infinitesimally small rate. We present a probabilistic model of such a system to show that the slotted ALOHA system with an infinite population is inherently unstable. This paper confirms the simulations and results of Kleinrock and Lam [8].

Fault detection process and system for a time-division switching network

Abstract: A fault detection process and system is disclosed for large multistage time division-space division-time division switching networks. In the input time-division switch an origin bit is simultaneously transmitted with each sample to the related output channel of the output time division switch. The origin bit is produced by modulating a selected bit of the input channel address by an associated sample parity bit. In the output switch the modulated origin bit is demodulated by the received sample parity bit. This demodulated origin bit is compared with the corresponding bit of the input channel address which has been stored in a memory of the output switch under control of the network computer unit. In addition, means are provided for taking into account input delay, transmission delay and output delay.

Time delay circuit for modems

Abstract: This invention relates to a time delay circuit for switching on and off modems used for data transmission over cables in local telephone networks. The time delay circuit comprises a shift register controlled by a signal pattern recognition circuit, to register signals representative of being information signals, a delay counter which is controlled to initiate a predetermined delay time at the occurrence of an information signal, and gating circuits controlled by said shift register and said delay counter to switch on the modem if solely information signals have been received during the delay time required by international conventions.

Analysis of overheads in packet-switched data networks

Abstract: Theoretical and simulation results are presented for the overheads in packet-switched networks. These overheads arise owing to the operational spects of the network and `blank' padding of the last packet of a message. Message lengths have been assumed to be exponentially distributed. Results indicate good agreement between theoretical and simulation results. It is concluded that overheads can be reduced in this case if the ratio of mean message length to packet length is kept high. In such cases, it is also possible to find an optimum packet size such that the combined overheads are minimised, under certain restrictions.

Optimum packet size in a packet-switched data network

Abstract: In packet-switched data networks, overheads are incurred primarily due to two aspects: the protocol, i.e. headers. acknowledgements etc. and blank padding of the partially used packet. In the letter, the overhead factors due to these two sources are derived under certain assumptions. Simulations using exponentially distributed messages have been carried out, and results from these are also presented. It is shown that, under certain conditions, it is possible to have a packet size that minimises the total overheads.

Throughput degradations for single packet messages

Abstract: The transmission of digitized speech over the ARPANET represents a new dimension in the use of packet switching systems. The throughput and delay requirements for this newly emerging application area are quite different from the throughput and delay requirements for interactive use or file transfers. In particular, we need to achieve a high throughput for small messages since long messages result in long source delays to fill the large buffers. Therefore we are currently studying the throughput limits for single-packet messages. We realize that up to now little attempt was made to optimize throughput for low delay traffic. It was nevertheless surprising for us to find out that the observed throughput for single-packet messages is in many cases only about one fourth of what one would expect. In what follows we are going to explain why this happens and what could be done to correct this situation. On April 1, 1974, we sent, using the IMP message generator, single-packet messages at the highest possible rate ("RFNM-driven") from the MOFFET-IMP to the SRI-IMP. There are two three-hop paths from MOFFET to SRI, one of them involving two 230.4 kbs circuits. Since there was hardly any interfering traffic we expected an average round-trip delay of not more than 100 msec. Assuming that there are, on an average, 3 messages in transmission between MOFFET and SRI and assuming a message length of about 1000 bits this should result in a throughout of more than 30 kbs. The observed through was, however, less than 8 kbs. A repetition of the experiment showed the same result. A more detailed analysis of the collected data revealed that an average number of 3.5 messages were simultaneously in transmission between MOFFET and SRI. The throughput degradation could therefore not have been due to interfering traffic between these two sites. Also the channel utilization for all channels that were involved in the transmission was less than 40 percent. The observed mean round-trip times between MOFFET and SRI, however, were about 500 msec. Since these large round-trip times were obviously not due to physical limitations, we studied the flow control mechanism for single-packet messages and were able to come up with an explanation for this undesirable behavior. When a single-packet message arrives at the destination IMP out of order (i.e., the logically preceding message has not yet arrived there) it is not accepted by the destination IMP. It is rather …

Note on Inherent and Imposed Priorities in Packet Switching

Abstract: When messages are transmitted as a series of possibly noncontiguous packets, an effective priority is introduced which favors short messages. The strength of this effect upon transmission time is investigated and compared with schemes where an additional priority scheme is imposed. It is found that imposing a real priority structure can markedly influence delays when: first, the trunks are relatively heavily loaded, and second, the nodes' incoming traffic arrives over high-speed channels.

On the Packet-Interleaved Interface Between Packet-Switched Network and Computers

Abstract: This paper describes a study of transmission control procedure for computer-to-computer and computer-computer-to-terminal communication through a public packet-switched network. Four types of basic data link are defined over a packet travel path in the network, and the functions required for the data link are discussed. A process number and its associated control method are proposed as a method of packet-interleaved communication. By applying the result of the discussion and introducing the concept of a data link and a process number, a transmission control method and a call control method between packet-switched network and computers are proposed for the packet-interleaved communication on the basis of the HDLC procedure (high-level data link control procedure).