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Optimizing the use of X and VNC protocols for support of remote observing Robert Kibricka, Steven L. Allena, Al Conradb, Terry Stickelb, and Gregory D. Wirthb aUCO/Lick Observatory, University of California, Santa Cruz, CA 95064 USA bW. M. Keck Observatory, Kamuela, HI 96743 USA ABSTRACT Remote observing is the dominant mode of operation for both Keck Telescopes and their associated instruments. Over 90% of all Keck observations are carried out remotely from the Keck Headquarters in Waimea, Hawaii (located 40 kilometers from the telescopes on the summit of Mauna Kea). In addition, an increasing number of observations are now conducted by geographically-dispersed observing teams, with some team members working from Waimea while others collaborate from Keck remote observing facilities located in California. Such facilities are now operational on the Santa Cruz and San Diego campuses of the University of California, and at the California Institute of Technology in Pasadena. This report describes our use of the X1 and VNC2 protocols for providing remote and shared graphical displays to distributed teams of observers and observing assistants located at multiple sites. We describe the results of tests involving both protocols, and explore the limitations and performance of each under different regimes of network bandwidth and latency. We also examine other constraints imposed by differences in the processing performance and bit depth of the various frame buffers used to generate these graphical displays. Other topics covered include the use of ssh3 tunnels for securely encapsulating both X and VNC protocol streams and the results of tests of ssh compression to improve performance under conditions of limited network bandwidth. We also examine trade-offs between different topologies for locating VNC servers and clients when sharing displays between multiple sites. Keywords: remote observing, X protocol, VNC protocol, ssh protocol 1. INTRODUCTION Over the past several years, the Internet-2 initiative has spurred significant improvements in network infrastruc- ture throughout the U.S. As a result, many Keck telescope observing programs can now be conducted remotely from any one of several Keck remote observing facilities located in California. Details of the motivation and planning for those facilities and the software architecture on which they are based were discussed in several previous reports.4–7 Key aspects of those reports are excerpted in Sections 1.4 and 1.5 below to provide the context for the sections that follow them. 1.1. The Keck Remote Observing Model Keck’s remote observing model was first adopted in 1996 and is based on two fundamental principles: 1) all observing applications (including user interfaces) run on summit control computers, and 2) the displays generated by those applications are re-directed to the remote sites from which the observers operate (See Fig. 1). This model provides a generic method for supporting remote operation of a large variety of both optical and infrared instruments, and ensures that all observers, regardless of the location from which they observe, run identical versions of the observing applications. Further author information- (Send correspondence to R.K.) R.K.: Email: [email protected]; http://www.ucolick.org/˜kibrick; Telephone: 831-459-2262; Fax: 831-459-2298; S.A.: Email: [email protected]; Telephone: 831-459-3046; Fax 831-459-2298; A.C.: Email: [email protected]; Telephone: 808-881-3812; Fax: 808-885-4464; T.S.: Email: [email protected]; Telephone: 808-885-7887; G.W: Email: [email protected]; Telephone: 808-885-7887 Observing Support Astronomer Assistant Astronomer X Video X Video X Video Display Conference Display Conference Display Conference W/S W/S W/S INET2 Fiber FR R F RR Remote Observing Net Keck Summit Net Keck HQ Net Santa Cruz, CA Mauna Kea, HI Waimea, HI T T Legend Control Control F - Firewall Computer Computer R - Router T - Telephone Co. Switch W/S - Workstation Telescope Instrument ISDN Circuit Figure 1. Global overview of connectivity between Santa Cruz, Mauna Kea, and Waimea 1.2. Motivation The primary motivation for this approach is to minimize the overall level of technical and administrative support required to maintain the operation of observing software at Keck. Under this model, only the single copy that runs on the summit control computers needs to be maintained. As a result, it also reduces the support burden at the remote sites, since the workstations used for remote observing only require installation and maintenance of generic software (e.g., the X Window system and VNC). This is of particular concern, given current efforts to reduce, consolidate, and centralize information technology support on each U.C. campus; those efforts are driven by budget cutbacks that are a result of California’s multi-billion-dollar State budget deficits. In addition, since different Keck instruments were developed by different institutions, there are significant differences in the way in which they operate and in the underlying communication protocols (e.g., RPC,8 EPICS channel access,9 MUSIC10) that they use. Some of those protocols are sensitive to packet throughput, latency, and jitter issues that are difficult to control across wide area networks (WAN), while others pose challenges in cases where firewalls need to be traversed. By requiring all observing software to run at the summit, these protocol issues are confined to the summit network. This simplifies the task of remote operation in that these WAN-related issues only need to be addressed for generic protocols, such as ssh, X and VNC. 1.3. Goals of the current effort While the Keck remote observing model provides the advantages noted above, it often does not deliver optimal interactive performance to all remote sites. In most cases, it delivers performance that is quite acceptable, but in a few cases interactive response is sluggish at best. A major goal of our current and ongoing effort is to experiment with various combinations of generic protocols to determine which ones provide the best overall performance over the widest range of circumstances. An additional goal of this effort is to enable summit observing support staff to monitor the operations conducted by observers from the remote sites. 1.4. Remote Observing from Keck Headquarters in Waimea Most observations with the Keck telescopes are now carried out from one of the two remote operations rooms located at Keck Headquarters in Waimea (see Fig. 2). The workstations in these rooms communicate with instrument and telescope control computers at the summit via a dedicated, 45 Mbit/sec fiber link (See Fig. 1). The observer is supported by an observing assistant (OA), who operates the telescope, and a support as- tronomer (SA), who assists the observer in setting up and operating the instrument. During the first part of the night, a SA is present in the remote operations room and during the latter part an on-call SA can be reached by telephone at home. The OA is usually located at the summit, but in some cases will operate the telescope from the same control room in Waimea from which the observer is running the instrument. A video-conferencing system links each remote operations room in Waimea with its corresponding telescope control room at the summit. Figure 2. Keck remote operations room in Waimea Figure 3. Santa Cruz remote observing room 1.5. The Keck Remote Observing Facilities in California The remote observing facilities in California (see Fig. 3) are primarily targeted towards observers scheduled for short-duration observing runs and who live within commuting distance of one of those facilities. They are not intended to duplicate the Waimea facility nor to operate independently of it. Rather, each is an extension of the facility in Waimea. That facility and those on the mainland are intended to operate in collaboration, sharing resources where practical. We rely on the existing instrument support staff at Waimea and provide video-conferencing and shared software environments so that they can most effectively support the observers at the mainland sites. In some cases, an observing run may be conducted by an observing team in which some of its members observe from Waimea while others elect to observe from the mainland. If an observing team is composed of observers from widely separated mainland sites (e.g., Santa Cruz and San Diego), then simultaneous remote operation for multiple mainland sites may prove desirable. A key objective of the mainland facilities is to provide observers with the flexibility to choose the observing site that is most practical and productive for them. That choice depends on the needs of the members of their observing team and the specific circumstances and duration of a given observing run. That objective can best be achieved if the mainland sites are operated in close collaboration and cooperation with the Waimea facility. 2. USING X PROTOCOL TO REDIRECT DISPLAYS TO REMOTE LOCATIONS In 1996, Keck initiated remote observing from its headquarters in Waimea. That initial implementation4 relied exclusively on the use of the X protocol to redirect to Waimea the displays generated by observing client applications running on the summit computers (See Fig. 4). Given the relatively high bandwidth and low latency (under 1 millisecond) between the two sites, this scheme worked relatively well and provided comparable interactive performance at both sites. Its main limitation was that multiple instances of a given client application needed to be run if the display from that application was needed at both sites. In the case of single-copy applications, their displays could be directed to one site or the other, but not simultaneously to both. Telescope Conrol Computer Instrument #1 Control Computer Telescope Conrol Computer Instrument #1 Control Computer Client Client Client Client App. App. App. App. SUMMIT SUMMIT Client Client Client Client Client Client Client Client App.

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