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The ADDRESS resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical address, used by a HOST or a ROUTER to find the physical address of another host on its network by sending a ARP QUERY packet that includes the IP address of the receiver.

The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.

The address resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical address, used by a host or a router to find the physical address of another host on its network by sending a ARP query packet that includes the IP address of the receiver.

The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.

The data UNIT created at the application layer is called a message, at the transport layer, 
the data unit created is called either a SEGMENT or an USER DATAGRAM, at the network layer,
the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a FRAME and finally transmitted as signals along the transmission media.

The data unit created at the application layer is called a message, at the transport layer, 
the data unit created is called either a segment or an user datagram, at the network layer,
the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a frame and finally transmitted as signals along the transmission media.

The data unit in the LLC level is called the protocol data unit (PDU). The PDU CONTAINS of FOUR fields a destination service access point (DSAP), a source service access point (SSAP), a CONTROL field and an information field. DSAP, SSAP are addresses USED by the LLC to identify the protocol stacks on the receiving and sending machines that are GENERATING and using the data. The control field specifies whether the PDU frame is a information frame (I - frame) or a supervisory frame (S - frame) or a unnumbered frame (U - frame).

The data unit in the LLC level is called the protocol data unit (PDU). The PDU contains of four fields a destination service access point (DSAP), a source service access point (SSAP), a control field and an information field. DSAP, SSAP are addresses used by the LLC to identify the protocol stacks on the receiving and sending machines that are generating and using the data. The control field specifies whether the PDU frame is a information frame (I - frame) or a supervisory frame (S - frame) or a unnumbered frame (U - frame).

The degeneration of a SIGNAL over DISTANCE on a network CABLE is called ATTENUATION.

The degeneration of a signal over distance on a network cable is called attenuation.

The function of PAD (Packet Assembler DISASSEMBLER) is described in a document known as X.3. The STANDARD protocol has been defined between the terminal and the PAD, called X.28; another standard protocol exists between the PAD and the NETWORK, called X.29. Together, these three RECOMMENDATIONS are often called "TRIPLE X".

The function of PAD (Packet Assembler Disassembler) is described in a document known as X.3. The standard protocol has been defined between the terminal and the PAD, called X.28; another standard protocol exists between the PAD and the network, called X.29. Together, these three recommendations are often called "triple X".

The HEADER should have a minimum length of 20 bytes and can have a maximum length of 60 bytes.

The header should have a minimum length of 20 bytes and can have a maximum length of 60 bytes.

The HELLO protocol USES TIME instead of distance to DETERMINE optimal routing. It is an ALTERNATIVE to the Routing INFORMATION Protocol.

The HELLO protocol uses time instead of distance to determine optimal routing. It is an alternative to the Routing Information Protocol.

The most common two letter combinations are CALLED as DIGRAMS. e.g. TH, in, er, re and an.
The most common three letter combinations are called as trigrams. e.g. the, ing, and, and ION.

The most common two letter combinations are called as digrams. e.g. th, in, er, re and an.
The most common three letter combinations are called as trigrams. e.g. the, ing, and, and ion.

The process that ALLOWS a NETWORK to self-repair networks problems. The STATIONS on the network NOTIFY the other stations on the ring when they are not receiving the transmissions. BEACONING is used in Token ring and FDDI networks.

The process that allows a network to self-repair networks problems. The stations on the network notify the other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token ring and FDDI networks.

The three types of ROUTING tables are fixed, dynamic, and fixed central. The fixed table must be manually modified every time there is a change. A dynamic table changes its information based on NETWORK TRAFFIC, reducing the amount of manual maintenance. A fixed central table lets a manager modify only one table, which is then read by other devices. The fixed central table reduces the need to update each machine's table, as with the fixed table. Usually a dynamic table causes the fewest PROBLEMS for a network administrator, although the table's contents can change WITHOUT the administrator being aware of the change.

The three types of routing tables are fixed, dynamic, and fixed central. The fixed table must be manually modified every time there is a change. A dynamic table changes its information based on network traffic, reducing the amount of manual maintenance. A fixed central table lets a manager modify only one table, which is then read by other devices. The fixed central table reduces the need to update each machine's table, as with the fixed table. Usually a dynamic table causes the fewest problems for a network administrator, although the table's contents can change without the administrator being aware of the change.

The Trivial File Transfer PROTOCOL (TFTP) allows a local host to obtain files from a remote host but does not provide reliability or security. It uses the fundamental packet delivery services offered by UDP.

The File Transfer Protocol (FTP) is the standard MECHANISM provided by TCP / IP for copying a file from one host to another. It uses the services offered by TCP and so is reliable and secure. It establishes two connections (virtual CIRCUITS) between the hosts, one for DATA transfer and another for control information.

The Trivial File Transfer Protocol (TFTP) allows a local host to obtain files from a remote host but does not provide reliability or security. It uses the fundamental packet delivery services offered by UDP.

The File Transfer Protocol (FTP) is the standard mechanism provided by TCP / IP for copying a file from one host to another. It uses the services offered by TCP and so is reliable and secure. It establishes two connections (virtual circuits) between the hosts, one for data transfer and another for control information.

Transmission is a physical movement of INFORMATION and concern issues LIKE bit polarity, synchronization, clock etc.
Communication means the MEANING full EXCHANGE of information between TWO communication media.

Transmission is a physical movement of information and concern issues like bit polarity, synchronization, clock etc.
Communication means the meaning full exchange of information between two communication media.

Virtual channel is NORMALLY a connection from one source to one DESTINATION, although multicast connections are ALSO PERMITTED. The other name for virtual channel is virtual CIRCUIT.

Virtual channel is normally a connection from one source to one destination, although multicast connections are also permitted. The other name for virtual channel is virtual circuit.

When hierarchical routing is used, the routers are divided into what we CALL regions, with each ROUTER knowing all the details about how to route PACKETS to destinations WITHIN its own region, but knowing nothing about the internal STRUCTURE of other regions.

When hierarchical routing is used, the routers are divided into what we call regions, with each router knowing all the details about how to route packets to destinations within its own region, but knowing nothing about the internal structure of other regions.

When the computers on the NETWORK SIMPLY listen and receive the SIGNAL, they are referred to as passive because they don’t AMPLIFY the signal in any way.
Example for passive topology - linear bus.

When the computers on the network simply listen and receive the signal, they are referred to as passive because they don’t amplify the signal in any way.
Example for passive topology - linear bus.

Wide-mouth frog is the simplest known KEY DISTRIBUTION center (KDC) authentication PROTOCOL.

Wide-mouth frog is the simplest known key distribution center (KDC) authentication protocol.

A stored procedure is named collection of SQL statements and procedural logic that is compiled, verified and stored in a server DATABASE. It is TYPICALLY treated like any other database object. Stored procedures ACCEPT input parameters so that a single procedure can be used over the network by MULTIPLE clients using different input data. A single remote message triggers the execution of a collection of stored SQL statements. The results is a reduction of network TRAFFIC and better performance.

A stored procedure is named collection of SQL statements and procedural logic that is compiled, verified and stored in a server database. It is typically treated like any other database object. Stored procedures accept input parameters so that a single procedure can be used over the network by multiple clients using different input data. A single remote message triggers the execution of a collection of stored SQL statements. The results is a reduction of network traffic and better performance.

ACID is a term COINED by Andrew Reuter in 1983, which STANDS for Atomicity, Consistence, ISOLATION and DURABILITY.

ACID is a term coined by Andrew Reuter in 1983, which stands for Atomicity, Consistence, Isolation and Durability.

EXTENDED SERVICES - These are add-on modular software COMPONENTS that are layered on TOP of base service.

Extended services - These are add-on modular software components that are layered on top of base service.

Client/Server applications development FRAMEWORK.
Firewalls of protection.
High AVAILABILITY.
Load balancing.
MOM integration.
SCALABILITY of functions.
Reduced system COST.

Client/Server applications development framework.
Firewalls of protection.
High availability.
Load balancing.
MOM integration.
Scalability of functions.
Reduced system cost.

DATABASE SERVERS
TP Monitors
Groupware
DISTRIBUTED OBJECTS
INTRANETS.

Database Servers
TP Monitors
Groupware
Distributed Objects
Intranets.

FILE servers are useful for SHARING files ACROSS a network. With a file SERVER, the client passes requests for file records over network to file server.

File servers are useful for sharing files across a network. With a file server, the client passes requests for file records over network to file server.

File servers
Database servers
TRANSACTION servers
Groupware servers
OBJECT servers
Web servers.

File servers
Database servers
Transaction servers
Groupware servers
Object servers
Web servers.

GENERAL MIDDLEWARE
Service-specific middleware.

General middleware
Service-specific middleware.

GROUPWARE ADDRESSES the management of semi-structured information such as text, image, mail, BULLETIN BOARDS and the flow of work. These Client/Server systems have PEOPLE in direct contact with other people.

Groupware addresses the management of semi-structured information such as text, image, mail, bulletin boards and the flow of work. These Client/Server systems have people in direct contact with other people.

HORIZONTAL scaling means adding or removing client workstations with only a SLIGHT performance impact. Vertical scaling means migrating to a larger and FASTER server MACHINE or multiservers.

Horizontal scaling means adding or removing client workstations with only a slight performance impact. Vertical scaling means migrating to a larger and faster server machine or multiservers.

If the BULK of the application runs on the CLIENT side, then it is Fat clients. It is used for DECISION support and personal software.

If the bulk of the application runs on the Server side, then it is Fat SERVERS. It tries to minimize network interchanges by creating more abstract levels of SERVICES.

If the bulk of the application runs on the Client side, then it is Fat clients. It is used for decision support and personal software.

If the bulk of the application runs on the Server side, then it is Fat servers. It tries to minimize network interchanges by creating more abstract levels of services.

If the NUMBER of incoming clients requests EXCEEDS the number of PROCESSES in a server class, the TP MONITOR may dynamically start new ONES and this is called Load balancing.

If the number of incoming clients requests exceeds the number of processes in a server class, the TP Monitor may dynamically start new ones and this is called Load balancing.

In 2-tier Client/Server SYSTEMS, the APPLICATION logic is either burried inside the user interface on the client or WITHIN the database on the server.
Example: FILE servers and Database servers with stored PROCEDURES.

In 2-tier Client/Server systems, the application logic is either burried inside the user interface on the client or within the database on the server.
Example: File servers and Database servers with stored procedures.

In 3-TIER Client/Server systems, the APPLICATION logic (or PROCESS) lives in the middle tier and it is SEPARATED from the data and the user interface. In theory, the 3-tier Client/Server systems are more scalable, robust and FLEXIBLE.
Example: TP monitor, Web.

In 3-tier Client/Server systems, the application logic (or process) lives in the middle tier and it is separated from the data and the user interface. In theory, the 3-tier Client/Server systems are more scalable, robust and flexible.
Example: TP monitor, Web.

In the transaction SERVER, the client component usually includes GUI and the server components usually consists of SQL transactions against a database. These APPLICATIONS are called OLTP (Online Transaction Processing) OLTP Applications typically, RECEIVE a fixed set of inputs from remote clients. PERFORM multiple pre-compiled SQL comments against a local database. Commit the work and RETURN a fixed set of results.

In the transaction server, the client component usually includes GUI and the server components usually consists of SQL transactions against a database. These applications are called OLTP (Online Transaction Processing) OLTP Applications typically, Receive a fixed set of inputs from remote clients. Perform multiple pre-compiled SQL comments against a local database. Commit the work and Return a fixed set of results.

It imposses hierarchy and a division of labour among processors. Only one DESIGNATED processor, the MASTER, controls (in a TIGHTLY coupled arrangement) slave processors dedicated to SPECIFIC functions.

It imposses hierarchy and a division of labour among processors. Only one designated processor, the master, controls (in a tightly coupled arrangement) slave processors dedicated to specific functions.

It is needed to accomplish a PARTICULAR Client/Server type of services which includes:-

• DATABASE specific middleware
• OLTP specific middleware
• Groupware specific middleware
• OBJECT specific middleware
• INTERNET specific middleware and
• SYSTEM management specific middleware.

It is needed to accomplish a particular Client/Server type of services which includes:-

It includes the communication stacks, DISTRIBUTED directories, AUTHENTICATION services, network time, RPC, Queuing services ALONG with the network OS extensions such as the distributed FILE and print services.

It includes the communication stacks, distributed directories, authentication services, network time, RPC, Queuing services along with the network OS extensions such as the distributed file and print services.

It treats all processors as equal. Any PROCESSOR can do the work of any other processor. Applications are DIVIDED into threads that can run concurrently on any available processor. Any processor in the pool can run the OS kernel and execute user-written threads.

It treats all processors as equal. Any processor can do the work of any other processor. Applications are divided into threads that can run concurrently on any available processor. Any processor in the pool can run the OS kernel and execute user-written threads.

It waits for client-initiated requests. Executes many requests at the same time. TAKES care of VIP clients first. INITIATES and runs background task ACTIVITY. KEEPS running. Grown bigger and faster.

It waits for client-initiated requests. Executes many requests at the same time. Takes care of VIP clients first. Initiates and runs background task activity. Keeps running. Grown bigger and faster.

Middleware is a DISTRIBUTED software needed to support interaction between clients and servers. In short, it is the software that is in the middle of the Client/Server systems and it acts as a bridge between the clients and servers. It starts with the API set on the client side that is USED to INVOKE a service and it covers the transmission of the request over the NETWORK and the resulting RESPONSE.

It neither includes the software that provides the actual service - that is in the servers domain nor the user interface or the application login - that's in clients domain.

Middleware is a distributed software needed to support interaction between clients and servers. In short, it is the software that is in the middle of the Client/Server systems and it acts as a bridge between the clients and servers. It starts with the API set on the client side that is used to invoke a service and it covers the transmission of the request over the network and the resulting response.

It neither includes the software that provides the actual service - that is in the servers domain nor the user interface or the application login - that's in clients domain.

MOM allows general purpose messages to be exchanged in a Client/Server system using message queues. Applications communicate over networks by simply putting messages in the queues and getting messages from queues. It typically PROVIDES a very simple high level APIs to its services.

MOM's messaging and queuing allow clients and SERVERS to communicate across a network without being linked by a PRIVATE, dedicated, logical CONNECTION. The clients and server can run at different times. It is a post-office like METAPHOR.

MOM allows general purpose messages to be exchanged in a Client/Server system using message queues. Applications communicate over networks by simply putting messages in the queues and getting messages from queues. It typically provides a very simple high level APIs to its services.

MOM's messaging and queuing allow clients and servers to communicate across a network without being linked by a private, dedicated, logical connection. The clients and server can run at different times. It is a post-office like metaphor.

Non-GUI Client: These are APPLICATIONS, generate server requests with a minimal amount of human interaction.

GUI Clients: These are applicatoins, where occassional requests to the server result from a human interacting with a GUI (Example: Windows 3.x, NT 3.5)

OOUI clients : These are applications, which are highly-iconic, object-oriented user interface that provides SEAMLESS access to information in very visual formats. (Example: MAC OS, Windows 95, NT 4.0)

Non-GUI Client: These are applications, generate server requests with a minimal amount of human interaction.

GUI Clients: These are applicatoins, where occassional requests to the server result from a human interacting with a GUI (Example: Windows 3.x, NT 3.5)

OOUI clients : These are applications, which are highly-iconic, object-oriented user interface that provides seamless access to information in very visual formats. (Example: MAC OS, Windows 95, NT 4.0)

Process-per-client ARCHITECTURE. (Example: Oracle 6, Informix )
MULTITHREADED Architecture. (Example: Sybase, SQL server)
Hybrid Architecture.

Process-per-client Architecture. (Example: Oracle 6, Informix )
Multithreaded Architecture. (Example: Sybase, SQL server)
Hybrid Architecture.

RESOURCE MANAGER
TRANSACTION Manager and
APPLICATION PROGRAM.

Resource Manager
Transaction Manager and
Application Program.

RPC hides the intricacies of the network by using the ordinary procedure call mechanism familiar to every PROGRAMMER. A client process calls a FUNCTION on a remote server and suspends itself until it gets back the results. Parameters are passed like in any ordinary procedure. The RPC, like an ordinary procedure, is synchoronous. The process that ISSUES the call WAITS until it gets the results.

Under the covers, the RPC run-time software collects values for the parameters, forms a message, and sends it to the remote server. The server receives the request, unpack the parameters, calls the procedures, and sends the reply back to the client. It is a telephone-like METAPHOR.

RPC hides the intricacies of the network by using the ordinary procedure call mechanism familiar to every programmer. A client process calls a function on a remote server and suspends itself until it gets back the results. Parameters are passed like in any ordinary procedure. The RPC, like an ordinary procedure, is synchoronous. The process that issues the call waits until it gets the results.

Under the covers, the RPC run-time software collects values for the parameters, forms a message, and sends it to the remote server. The server receives the request, unpack the parameters, calls the procedures, and sends the reply back to the client. It is a telephone-like metaphor.

SQL is a POWERFUL set-oriented language which was developed by IBM research for the databases that adhere to the relational model. It CONSISTS of a short list of powerful, yet highly FLEXIBLE, commands that can be used to manipulate information collected in TABLES. Through SQL, we can manipulate and control sets of records at a time.

SQL is a powerful set-oriented language which was developed by IBM research for the databases that adhere to the relational model. It consists of a short list of powerful, yet highly flexible, commands that can be used to manipulate information collected in tables. Through SQL, we can manipulate and control sets of records at a time.

• SERVICE
• Shared resources
• Asymmentrical protocols
• Transparency of location
• Mix-and-match
• Message based exchanges
• Encapsulation of services
• Scalability
• Integrity
• Client/Server computing is the ultimate "Open platform". It gives the FREEDOM to mix-and-match components of ALMOST any level. Clients and servers are loosely coupled systems that INTERACT through a message-passing mechanism.

• SQL is an interactive query language for ADHOC database queries.
• SQL is a database programming language.
• SQL is a DATA DEFINITION and data administration language.
• SQL is the language of networked database servers
• SQL helps protect the data in a multi-user networked environment.

Because of these multifacted roles it plays, physicists might CALL SQL as "The grand unified THEORY of database".

Because of these multifacted roles it plays, physicists might call SQL as "The grand unified theory of database".

• TASK preemption
• Task priority
• SEMAPHORES
• Interprocess COMMUNICATIONS (IPC)
• Local/Remote Interprocess communication
• Threads
• Intertask protection
• Multiuser
• High performance file system
• Efficient memory management and
• DYNAMICALLY linked Run-time extensions.

• TRANSPORT STACK
• NETWORK OS
• Service-specific MIDDLEWARE.

• The CLIENT side building BLOCK runs the client side of the APPLICATION.
• The SERVER side building block runs the server side of the application.

• The CLIENT
• The SERVER and
• MIDDLEWARE.

The GROUPED SQL statements are CALLED Transactions (or) A TRANSACTION is a collection of actions embused with ACID properties.

The grouped SQL statements are called Transactions (or) A transaction is a collection of actions embused with ACID properties.