NetWeave - Open Access to Legacy Systems

1. NetWeave - Open Access to LegacySystems Prem S Somu 11/15/99 Courtesy: NetWeave Coporation (http://www.netweave.com)

2. Open Access to Legacy Systems Allowsto interconnect yesterday’s incompatible legacy systems to make them tomorrow’s open and distributed systems Enables a program on a machine to run on a different machine irrespective of the O/S and architecture

3. Open Access Contd. Applications can reach to the remote data and processes of the following: Host MainframesWorkstationsSQL Databases IBM PC DOS Oracle Digital PC Windows Sybase Tandem NT Informix Stratus OS/2 Ingres Unisys Unix Unix Macintosh

4. NetWeave Architecture • Architecture is based on NetWeave Server, which consists of 3 layers • Netweave Kernel • Communication Layer • Services Layer • One Netweave Server for each and every machine on the network

5. Architecture Cond. The Kernel : • It provides all control, routing, data conversion and service invocation • required by NetWeave Agent • It uses NetWeave replicated dictionary containing object names and • locations Communication Layer : • Number of protocol stacks bound into it for the various protocols • it has to handle Services Layer : • All the services required by the NetWeave Agent are bound into this layer

6. Middleware Services • Transaction Services • Client is responsible for presentation services, editing of incoming data and • formatting of the outgoing data. • Server is responsible for implementing the business logic • Message Broadcast Services • Used to synchronize applications • Doesn’t depend on hardware capabilities • Database services • The application as a whole acts as a client to a remote database server • So, applications can be written solely on the client system with no prior • knowledge of the server

7. Middleware Services Contd. • Replication Services • Replication of the data is done at the workstations • The updates will not be written to the local copy but to the copy at the server • All the updates will be broadcast to all or interested clients • (including to the originator) immediately and the clients may also request • for notification of the updates • The host server guarantees notification of the updates to the clients • as in AFS • Concurrency control is provided by locking

8. Ancillary Services • Data Conversion Services • To reconcile differences in data formats between diverse platforms • Directory Services • The client need only know about a file by a pseudonym, like PAYROLL file • File transfer Services • Just acts like FTP, but the data in the file will be converted to suite that • platform • Remote Spooling Services • The beauty is, you can send a file resting on a remote platform • to a remote spooler for printing etc.

9. Ancillary Services Contd. • Dual LAN Support • The workstations involved in mission-critical applications and the servers • are connected not by one but with two LANs • The second LAN is not a standby one, NetWeave uses both the LANs • in normal conditions, but if one fails it uses the other • Security Services • Security is implemented by challenge/response protocol • The challenge can anything between a simple password or a token

10. NetWeave Applications It finds applications in any area which uses co-operative processing among different operating systems • Power at the Desktop : provides client/server functions necessary to support • the partial migration of application functions to the desktop • ex: PPG - for decision support systems • Peer - to - Peer Application : It supports peer-to-peer co-operative applications • where the application may span different systems • ex: Apple Computers for inventory control • Migration : During migration, applications on one platform must communicate • with applications on other platforms and be able to access and update the data • ex: COMSAT onto a VAX system

11. Applications Contd. • Data Replication: When a reasonably up-to-date data but not with absolute • synchronization is needed • ex: Amtrak used to depict the state of the railroad on each of the • many consoles • Legacy System Investment Protection: Corporate America has invested billions • of dollars in Legacy systems wishes to have that open system but doesn’t • want to loose even a single dollar • ex: ATM Security Trading: obtain stock quotes, buy and sell stock • from an ATM • “Open System” application: Are the open systems really ‘open’. How does a • UNIX application access PC files • ex: Dell Computer

12. Conclusions • Each database operation must be sent individually over the network • The catch - network congestion !!!! • Updates are done at the server instead of at the local machine, • so the copies at all the clients will be up-to-date at all time • Because of the dual LAN support the initial cost will be high • No caching has been implemented • It’s the only commercially available software to make otherwise • incompatible legacy systems into an open, distributed system