Vaughan Wesson, February 2003.

Introduction

This technical note covers the general philosophy of using the Internet to transfer data, the various components in the system and then describes in detail how this is implemented with the Kelunji D Series recorder.

A useful glossary of Internet terms is available as TN200302D.

Internet telemetry is the term used by the SRC to describe the use of the Internet (or more precisely IP based communications) as a significant link in the chain between a recorder and the analysis centre. There are a number of advantages of this system including:

• The cost of sending the data is independent of the distance travelled
• The Internet is a very reliable communications medium with much built in redundancy
• TCP/IP is a well tested, reliable set of communications protocols providing the basis for a number of higher level protocols such as FTP (file transfers), SMTP/POP3 (email) and HTTP (Web)
• Multiple communication sessions can be handled simultaneously on one IP based link. For example an FTP file transfer and a Web exchange can be handled simultaneously without any additional protocols
• Access points to the Internet are becoming more common and access is becoming cheaper as more and more companies and individuals use the Internet for business and pleasure

Components of the System

The components of the system can generally be described as the chain:

Kelunji <-> ISP <-> Internet <-> ISP <-> Analysis Centre

That is, the Kelunji connects to an Internet Service Provider (ISP) which is connected to the Internet. Similarly, the analysis centre (or data management centre or whatever) is also connected via an ISP to the Internet. The IP based protocols (see glossary) are used to transfer (route) the information from the Kelunji, through its ISP, through the Internet, through the other ISP to the analysis centre and vice versa.

The Internet

The Internet is often drawn as a fussy cloud or some other vague shape as it is difficult to describe it as having any physical form. It is a collection of cables and satellite links providing a series of communication channels between devices. It is the Internet Protocol (IP) that is the common factor allowing all the various devices to communicate with each other.

Internet Service Providers

The ISP's provide the ability for normal users to connect to The Internet. They will typically have more than one communication channel to The Internet backbone to provide a secure service and allow users to connect to them using various means. The most common means are:

• Dial up modem
• ADSL modem
• Cable modem
• ISDN
• Radio modem
• High speed digital cable

For example, ES&S has an ADSL connection to its ISP, while at home I have a cable connection to mine and many of our seismographs use a dial up modem connection. The main differences between the systems are speed, reliability and cost.

A useful resource for obtaining details about local ISP's in Australia can be found here. With this site you can search for an ISP using either a phone number or geographically.

If just sending triggered data files, a cheap Internet account may be used. Either one based on connection time (around $1 per hour) or a fixed monthly account with a limited number of hours can be used. However, for continuous data a more expensive account allowing for continuous connection is required. Finally, a fixed IP address for the site will usually cost more again.

Analysis Centre

The analysis centre is where all the data ends up. For the Kelunji Internet telemetry services, all that is required in (or associated with) the analysis centre is an FTP server. This is what the Kelunji will send the data files to. The Kelunji has settings for a user name and password for connecting to the FTP server and a directory may also be specified for where the files are to be stored. As of version V5.11A, the Kelunji supports both active and passive mode FTP file transfers, so should work with all FTP servers.

To make best use of the data, the SRC's eqLogger and eqWatch programs are designed to process continuous and triggered files respectively as produced by the Kelunji.

Kelunji Data Communications via the Internet

The Kelunji contains software to perform IP based communications and can therefore connect directly to an ISP or a computer. At present, Guria (V5.10A through to V5.11A) provides the following Internet based services:

• Sending of triggered data files via FTP. These may contain none, some or all of the channels being sampled and may optionally be compressed. If no channels are selected, only the trigger time and amplitude information are sent.
• Sending of continuous data files via FTP. These may contain some or all of the channels being continuously recorded and may optionally be compressed.
• Sending of a State-of-Health file via FTP at a specified interval. Since every trigger file also includes this state of health information, if a trigger file has been sent in the required time interval then the extra file is not sent.
• Running an FTP server. This allows standard PC's to examine the files present, retrieve them, delete them and so on as required.
• Running a Web server. This allows a user to connect using a standard Web browser. At present many, but not all, functions of the Kelunji are available through the Web based interface. For example, the recorders operation can be checked, data files viewed and some settings altered.

In the near future, we will be adding email support. This will provide some or all of the following additional services:

• Sending of triggered data files via email
• Sending state of health files via email
• AutoDRM for a variety of information including waveforms
• Receiving email commands to change operating parameters

The listed services are available through either an Ethernet connection or a serial connection using PPP. The Ethernet interface is faster but uses more power and may not be available in some situations. The PPP interface will probably be the most common in the field.

Network Interfaces

The Kelunji Internet connectivity is provided through what it calls its "Network interfaces". These are set up in the "Settings:Serial:Network interfaces" menu. For versions up to at least V5.11A only one interface is supported, but the code is written to support up to four separate interfaces - for example, one Ethernet and three PPP. Each interface may be operated in one of three modes:

Mode 0 - Permanent

In this mode, the Kelunji will try and keep the interface open at all times. For example if a phone call through a modem is dropped for some reason, the software will recognise this after some time and attempt to re-establish the connection.

Mode 1 - On Demand

In this mode, the Kelunji will normally have the modem set waiting to answer a phone call and establish a PPP connection. However, when it is required to send a file (e.g. after triggering), it will initiate a connection to the ISP as specified. After the file has been transferred, the connection will be closed and the Kelunji will revert to waiting for a phone call.

Mode 2 - Send Only

In this mode, the connection is usually closed. When it is required to send a file, the connection is opened, the file sent and then the connection is closed again.

Obviously, the mode to use will depend on what services are being used. Mode 0 (permanent) is the usual mode if continuous data files are being sent or either the FTP or Web server is required. Mode 2 (send only) will yield the lowest cost and power consumption if using a modem powered from the Kelunji.

Each interface has its own IP address. This may be obtained as part of the PPP negotiation process. It also has its own network mask, gateway address and up to three DNS server addresses. The PPP negotiation will also attempt to obtain a DNS server address from the ISP. The DNS servers are queried in turn to convert a domain name to an IP address if required.

PPP Interfaces

The Kelunji contains up to four serial ports that may be used for PPP connections. These are the Console ("Serial") port and the three Digitiser ports. Where possible, it is best to leave the Console port for a user terminal and use one of the Digitiser ports for the modem to connect to the ISP.

For PPP interfaces additional settings are available.

• An initialisation string for the modem. A typical string would be AT&F&D0&K0L3
• The power for the modem may come from the Digitiser port, the alarm/timing port or neither. Where possible it is best to power the modem from the Kelunji as then the Kelunji can power cycle the modem if required
• A number of seconds delay may be specified after the modem power is applied. For a landline modem this may be 5 or 10 seconds, but for a GSM modem it may be 20 or 30 seconds to allow the modem to "find" the network
• The phone number of the ISP may be specified. Alternatively, if a direct cable to a PC is desired then the strings WINNT or WIN95 may be specified to indicate this. The machine being connected to must be running Remote Access Server or a similar program
• Limits on the number of phone calls per day and minimum number of minutes between calls are possible. These limits are discussed below
• The user name and password to supply to the ISP

The limits on the phone calls are required to cope with situations where the Kelunji cannot establish a connection to the ISP for some reason. The first limit is the number of calls allowed in one 24 hour period from 0000 UT one day to 0000 UT the next day. Each time the Kelunji attempts to dial the ISP is considered one phone call (note that it does not have to actually connect for it to be counted). The second parameter forces a minimum time between phone calls. This is designed to cope with periods of congestion on the GSM network for example. The time is measured from when the previous call was attempted.

Ethernet Interface

A single 10 Mbit/s Ethernet interface is provided on the Kelunji recorder. This can be used for either twisted pair or coaxial cables. With the Ethernet enabled, the Kelunji power consumption increases considerably. This is from a combination of the power drawn by the Ethernet transceiver itself and the fact that the processor is required to run at high speed all the time rather than sleeping when no tasks are to be performed.

When using the Ethernet interface, the network mask and gateway address will usually be required.

An Ethernet port has a unique address assigned to it by the manufacturer, known as its MAC address. This is a 48 bit number usually written as six 8 bit numbers each written in hex and separated by either a hyphen or a colon. For example 08:00:69:02:1D:FC or 08-00-69-02-1D-FC. Each manufacturer obtains an allocation of address from the Institute of Electrical and Electronics Engineers, Inc (IEEE) usually by obtaining an "Organisationally Unique Identifier" (OUI) which is a three byte value that may be used as the first three bytes of an Ethernet address. Environmental Systems and Services has the OUI of 00-0B-22. For the Kelunji D series, its Ethernet MAC address is obtained by combing our OUI with the serial number of the DK board. Therefore the MAC address of DK board number 77 would be 00-0B-22-00-00-4D.

File Transfer Steps

This section lists the steps the Kelunji takes in sending a file via FTP. It includes the messages that may appear if the diagnostic debug messages are enabled.

There is a task in the recorders software that is dedicated to sending files via FTP. This task may be "triggered" by any of the following events:

• Expiration of a dedicated timer (180 seconds pre V5.11A, now 133 seconds)
• Creation of a trigger file or continuous recording file to be sent via FTP
• Creating of a state-of-health file
• Creation of an Intensity peak file
• Creation of a Finish Time file
• A Network Interface (PPP or Ethernet) successfully opening

Any files to be sent via FTP are written to either the FTP_CONT or FTP_TRIG directories. Continuous data files are stored in the FTP_CONT directory, all others are in the FTP_TRIG directory. Note that when using multiple drives, these directories will be present on ALL drives.

However the task is triggered, the same steps are followed. These are:

• If triggering is enabled and we have selected that trigger files will be FTPed, or we are calculating intensity and we have selected to FTP Intensity peaks THEN check and send files from the FTP_TRIG directory
• If continuous recording is enabled and we have selected that continuous data files will be FTPed THEN check and send files from the FTP_CONT directory
• Go back to sleep waiting for the next "trigger"

Check and Send Files From a Directory

Send a Group of Files

Open an Interface

Open an Ethernet Interface

Open a PPP Interface

Dial Modem and Connect to ISP

Send a File

Close the Interface