Network Upgrade for the Slc: Control System Modifications
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چکیده
Current communications between the SLAC Linear Collider control system central host and the SLCmicros is built upon the SLAC developed SLCNET communication hardware and protocols. We will describe how the Internet Suite of protocols (TCP/IP) are used to replace the SLCNET protocol interface. The major communication pathways and their individual requirements are described. A proxy server is used to reduce the number of total system TCP/IP connections. The SLCmicros were upgraded to use Ethernet and TCP/IP as well as SLCNET. Design choices and implementation experiences are addressed. I. CURRENT SLC CONTROL SYSTEM The current SLC Control System micro communication services are based on the SLCNET communications protocol. The SLCNET system was developed at SLAC in the 1980’s and consists of a master node and up to 255 slave nodes connected by custom hardware and software. The master, or VMS central host is a DEC Alpha computer running the OpenVMS operating system. The slaves, or SLCmicros, are Intel ix86 single board computers in Multibus I crates running the iRMX real time operating system. The SLCNET clock rate is one megahertz and the protocol used is SDLC. Message passing is supported between individual processes on the VMS host to individual tasks on the SLCmicros. The most prevalent VMS host process is the SLC Control Program or (SCP), of which there can be many running concurrently. The SCP provides the main user interface to the SLC Control System. There are also stand-alone processes which communicate directly to the SLCmicros to collect error reports, distribute database and timing information. All together this involves 50-100 processes on the VMS host communicating with 1-10 tasks on the SLCmicros. The basic tools to boot, debug, and query diagnostic information from the SLCmicros are also available over SLCNET. The VMS host is equipped with Ethernet and FDDI interfaces which provides support for TCP/IP. The VMS host TCP/IP stack is Multinet which provides communications to various network nodes used in the control system such as EPICS nodes, X-terminals and others. The SLCmicros do not presently support Ethernet or TCP/IP. II. ENTER ETHERNET AND TCP/IP The decision to upgrade the SLC Control System VMS host and SLCmicros to use TCP/IP protocols was based on projected bandwidth requirements, hardware availability, and maintenance issues. Please refer to the network upgrade paper for more information1. The upgrade of the SLC Control System and the SLCmicros would make TCP/IP the common communications protocol for all PEP-II control system nodes. This upgrade project required that code be modified or written for both the VMS host and the SLCmicros. This code supports both SLCNET and TCP/IP communications paths since we plan to upgrade as schedule and budget constraints permit. There are some applications that require significant modifications and others that require complete new software to use TCP/IP. The TCP stream-based protocol was chosen for nearly all the applications since a reliable data stream with flow control is required. TCP connections are setup once and remain for the lifetime of the SLCmicro task or VMS host process. This reduces connection overhead. Since the VMS host and the SLCmicros enjoy the same byte alignment, the data will be passed in little-endian order. The Multinet package on the VMS host supports both TCP/IP BSD3.4 socket interface and the standard VMS QIO interface. The SLCmicro uses the Fusion TCP/IP stack ported to the iRMX operating system
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تاریخ انتشار 1998