The GDPS data handling system can be subdivided into three main functional sub-systems:

• Communication Links
• Automatic Message Switching and Data Base Management
• Products Generating/Applications

The Application subsystem can, in turn, be divided into several modules, which can be independently implemented.

The WMO GTS circuits use both terrestrial and satellite communication links to provide NMCs with different types of meteorological data and products; which can be in text, GRIB, BUFF, Satellite and Radar image format.

Presently, several satellite-based data distribution systems are available to Members of RA I , which include:

• The Meteorological Data Distribution (MDD)
• The International Satellite Communication System (ISCS)
• SADIS
• RETIM and FAX-E (for North Africa )

To be able to receive and display satellite data/products the NMCs and RTHs require ground equipment, which include receivers and computers. By the year 2003, all current MDD, DRS and DCP services and the HRI and WEFAX which are provided by METEOSAT will be replaced by fully digital LRIT and HRIT of the MSG receiving systems. This requires new ground receiving equipment.

At an NMC different types of data such as synoptic, upper air, etc., may be received through a variety of means.

• Radio
• Telegraphic lines
• Telephone/data lines, fax
• Dedicated data lines using X.25 or IP protocols.
• Internet (e-mail, FTP Server)

Where national observing stations are spread over large areas and are at long distances to the NMC, it may be cost-effective, in a number of ways, to group them into zones and then establish a medium speed link to one station within a designated zone as "zone office". Resources permitting and where the technology exists, the zone offices could be networked using Frame Relay on the Public Telephone Network System to form a single "Cloud". The practical benefits of the cloud approach include:

• Cost Effectiveness

• Generally more cost-effective then dedicated leased circuits.
• Economy of scale for large centres.
• Capacity can be selected incrementally.

• Flexibility

• Virtual circuits can be added and removed easily.
• Virtual circuits' capacity can easily be adapted.

• Technical support and services from the Network Services provider facilitates operation and management.

• Opportunity to accelerate TCP/IP implementation.

The implementation of a cloud which extends beyond single NMC, while has benefits, has problems regarding:

• Standardisation of the cloud system.
• Sharing of costs.
• Security aspects related to TCP/IP and a mixed Internet/GTS environment.

Could the following political groupings in RA I be used to bring about the establishment of clouds?

• ASECNA which already has SATCOM.
• SADC which is planning for a telecommunication network for civil aviation.
• IGAD which could establish another cloud covering the Horn of Africa, etc.

The strategic direction in the development of the GTS is based on the Open System Interconnections (OSI) as set out by the International Standards Organisation (ISO). In consideration of the hyper evolution of the Internet and the supporting technical standards, vis-à-vis, WMO is expanding functional needs of its various programs. The WMO has decided to replace X.25 with IP of the TCP/IP protocol suite for supporting GTS operational needs.

The OSI is a layered model consisting of seven layers. There are several protocols, which operate in the network layer (third layer) of this model including: IP, CLNP, IPX, etc. The WMO has chosen the IP protocol because:

• IP (TCP/IP) is more or less the Internet Industry Standard and vendors are now concentrating on this protocol, thus making it relatively cheap and very popular.
• IP (TCP/IP) supports numerous applications which are available off-the-shelf, e.g. telnet, FTP, e-mail, web browsers, multimedia, RAS, etc.

• IP (TCP/IP) is routable and offers connectivity in a heterogeneous environment, thus enabling it to connect and inter-operate with many other TCP/IP-based hosts such as UNIX, VMS, IBM Mainframes, Macintosh, etc.

These IP (TCP/IP ) characteristics ensure savings in both direct costs and in the cost of human resources development. However, a wide spread application of IP protocol on the GTS requires not only adoption of switching applications, naming convention and IP address convention but also a very serious security consideration. These are some of the things which stand as challenges to the WMO as the Organisation contemplates applying Internet technology to the process of building up an improved GTS.

The Internet is a global network of PC networks. It is an open system as opposed to the likes of CompuServe, AOL, the WMO GTS, etc., which are basically closed systems. Several services are presently available on the Internet:

• e-mail
• File Transfer
• Web Browsing, etc.

The commercial closed systems are collaborating with the Internet by making themselves gateways to these services, thus acting as ISPs, so too the WMO GTS. Using the above Internet services an NMCs could:

• Complement GTS function of data and products exchange

• Reach the "world" both in providing its services and products; and in its own general exposure

• Interact with each other and the WMO Secretariat. etc

but considering:

• that evolution of the Internet is just as phenomenon as it is unpredictable, being driven and controlled only by market forces and so making its present (year 2000) performance, in terms of GTS data/products transmission, unpredictable due to its variable load and hyper growth.

• that one of the most important functions of the GTS is to provide a SURE means of real-time data handling capability to NMCS.

• that at certain NMCs, as a result of the local telecommunication infrastructure, Internet availability may be at an unacceptable low level.

There is a need to protect the WMO GTS operating in a mixed environment with Internet.

But from where, exactly, the GTS be protected? The GTS should be protected from the adverse results of the modalities of its interaction with the Internet and its technology. The nature of the mix in the application of GTS and Internet technology. The mix can be as outlined below.

In this scenario the GTS is viewed as a closed private network system - an INTRANET- in which:

• IP addressing would be private and unlimited.
• Security concern would be much reduced.
• The WMO would take charge of its own destiny while enjoying the benefits of Internet technology.

Assuming that Internet security issues have been resolved satisfactorily and WMO, therefore, decides to replace the complete GTS with the Internet system. In this situation the following remarks are pertinent:

• The WMO will, from then on, have to manage the GTS according to the rules of the Internet; with all its unpredictability. For example, the WMO will need to modify some of its GTS procedures to fit into Internet rules, such as rules regarding IP addressing

• The WMO will have to ensure that it provides the fast response to change the market-force-driven that the Internet goes through.

• With Internet’s hyper growth it is unlikely that many of RA I Telecommunication Institutions will provide services to the level required by GTS real-time data and products communications. The Internet is already very crowded and in RA I speeds to access is relatively low.

In the countries where Internet put through is high and connection tariffs are cost-effective the less time-critical meteorological data and products can gradually be put on the Internet. The gradual approach is preferred not only to ensure non-interruption to data/products transmissions but also to protect the investment of the NMCs in RA I have made on GTS. Besides, the WMO itself requires time to prepare guidelines on Internet implementation, design Internet compatible data/products formats etc.