1. Define RPC
RPC-Remote Procedure Call
RPC like an ordinary procedure call is synchronous. 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.
2. What are the issues faced in RPC?
1. The issues in RPC are:
a. How are the servers functions located and started?
b. How are parameters defined and passed between the client and the server?
c. How are failures handled?
d. How is security handled by RPC?
e. How does the client find its server?
f. How is data representation across systems handled?
3. Define IDL.
IDL-Interface Definition Language
IDL (Interface Definition Language) describes the functions and parameters that a server exports to its clients. An IDL complier takes these descriptions and produces source code stubs (and header files) for both client and server.
4. Define binding.
The association of a client with a server is called binding. The binding information can be hard coded in the client or a client can find its server by consulting a configuration file or an environment parameter.
5. Define automatic binding and dynamic binding.
· The process of using a directory to find a server at runtime is called dynamic binding.
· The easiest way of finding a server with the help of RPC is called automatic binding, where the RPC client stub will locate a server from a list of servers that supports the interface.
6. Define persistent and non-persistent message queues.
· Persistent (logged on disk) messages are slower and they can be recovered in case of power failures after a system restart.
· Non Persistent messages refer to message queues in memory.
In both the cases messages can be copied or removed from a queue.
7. Differences between MOM and RPC.
Features / MOM: Messaging and / RPC: Remote procedure callQueuing
Metaphor / Post office-like / Telephone- like
Client/server relationship / Asynchronous .Clients and Servers operate at different Times and speed
Synchronous. Client and
Server must run concurrently.
Client/server sequencing / No fixed sequence / Servers must come up before
clients can talk to them.
Style / Queued / Call-Return
8. Define Kerberos.
Kerberos is the trusted third party that allows to processes to prove to each other that they are who they claims to be. Kerberos authentication system is widely implemented in distributed Computing Environment (DCE).
9. Define ACL (Access Control List)
Servers use access control list (ACLs) to control user access. ACLs can be associated with any computer resource. They contain list of names and the type of operations they are permitted to perform on each resource.
10. Define DFS.
DFS-Distributed File System
DFS provides a single image file system that can be distributed across a group of file servers. The DFS file naming scheme is location independent. Each file has a unique identifier that is consistent across network.
11. Define DCE cell.
DCE divides the distributed environment into administrative units (or domains) called cells. A DCE cell is a combination of client and server workstations.
A cell usually consists of the set of machines used by one or more groups working on related tasks. A DCE cell must have one directory server and one security server.
12. Name the elements of DCE directory services. DCE directory services consist of:
· Cell directory services (CDS)
· Global directory services (GDS)
This two tier hierarchy provides local naming autonomy (at the cell level) and global interoperability (at the inter cell level).
13. Define Authentication.
Authentication validates a client, typically a user or program is who or what it claims to be. In time shared systems, the authentication is done by the OS using passwords.DCE implements authentication by Kerberos.
102. Define Authorization.
Authorization comes after authentication; it determines whether the authenticated client has permission to access a resource. DCE supports authorization through Access Control List (ACLs).
14. Define DCE threads package.
The DCE thread package provides granular levels of multitasking on operating systems that do not provide multitasking threads.DCE thread packages support multitasking environments using shared memory.DCE provides a semaphore service that helps threads synchronize their access to shared memory.
15. What are the names of protocol introduced by Netscape navigator?
SSL(Secure Socket Layer) S-HTTP(Secure –HTTP) Firewalls
16. Define CGI.
CGI-Common Gateway Interface
CGI is now being used to access every known server environment .
CGI is a standard for interfacing external applications with information servers, such as HTTP or Web servers.
17. Define Hypertext.
Hypertext is a software mechanism that links documents to other related documents on the same machine or across networks. The linked document can itself contains links to other documents, and this can go on forever. A link can also point to other external resources such as image files, sound clips or executable programs.
18. Give some example for Internet Application Protocols.
o Simple Mail Transfer Protocol(SMTP)
o File Transfer Protocol(FTP)
o Network News Transfer Protocol(NNTP)
19. Define 3-Tier client/server
In 3-tier client/server systems, the application logic(or process) lives in the middle-tier; it is separated from the data and user interface.3-tier client/server systems are more scalable, robust and flexible. Examples of 3 tier client/server systems are TP monitors, distributed objects and the web.
20. What is the presentation layer?
The GUI is the "top layer". It contains all things that are visible to the user, the 'outside' of the system, such as screen layout and navigation. The GUI layer has techniques like HTML, CSS, Applet, Servlet, JSP, JHTML.
21. What is the Object layer?
This is the core of the system, the linking pin between the other layers. The object layer has
knowledge, in two different ways:
i. runtime values, like the customer name "Oxford & Associates" or the invoice number "OAA2000w36".
ii. Structural knowledge, about data and processing.
Data example
A customer can receive many invoices, and an invoice always goes to just one
customer.
Process example
Know who does what. Every object knows his own methods, and those of his neighbours. In a pure OO model an object talks to his neighbours, and nobody but his neighbours. In the object layer you'll find things like Classes, objects, instance variables, vectors, primitives, methods, polymorphism, encapsulation and inheritance. The objects mostly have a temporary nature. They "live" just in memory for the duration of a transaction or session.
22. What is the Database Layer?
The database layer takes care of persistency. An object from the object layer can write itself to one or more tables. In the database layer you'll find things like database, connection, table, SQL and result set.
23. Why web browsers are referred as ‘Universal clients’?
web browser is a minimalist client that interprets information it receives from a server, and displays it graphically to user. The client is simply there to interpret the server’s commands and render the contents of an HTML page to an user.
24. What are the steps involved in client/server interaction?
i. Select a target URL
ii. Browser sends an HTPP request to server
iii. Server comes to life and processes the request
iv. Browser interprets the HTML commands and displays the page contents.
25. What are parts of the URL?
The parts of URL include:
1) The protocol scheme-It tells the web browser which internet protocol to use when accessing a resource on a server.
2) The server name-It is usually an internet host domain name that identifies the site on which the server is running.
3) The port number-It identifies a program that runs on a particular server.
4) The path to a target resource-It starts with the slash after the host and the port number.
16 Marks Questions and hints
1. 3-tier Client/Server System.
Technologies
The technology requirements at the three level of architecture are different. Let us examine the Requirements at these levels and the matching technologies available in the market today Application Processing provided by multiple tiers there are:
1. PC Workstation (Presentation layer)
2. Application Server
3. Database Server
3-Tier Architecture Considerations:
Ø Client program contains presentation logic only
· Less resources needed for client workstation
· No client modification if database location changes
· Less code to distribute to client workstations
Ø One server handles many client requests
· More resources available for server program
· Reduces data traffic on the network
2. What are the basic building blocks in Client/Server System? And Explain
each Situation of building blocks arrangements.
Client building block.
The client building block runs the client side of the application. It runs on the operating system (OS) that provides graphical user Interface (GUI) or an OOUI (Object oriented User Interface) that access distributed services, wherever they may be.
Server building block.
The server building block runs the server side of the application. The server application typically runs on top of some shrink-wrapped server software package. The server side depends on the operating system to interface with middleware building block that brings in the requests for the service.
Middleware building block.
The middleware running block runs both the client and server sides of an application. It is of three categories: transport stacks, network operating systems (NOSs), and the service-specific middleware.
And explain about N tier system Architecture
3. What is Middleware? Briefly explain each type of Middleware?
o Define Middleware
o All types of middleware
o General Middleware
o Service-specific Middleware
4. Explain RPC.
Define RPC What are the issues faced in RPC
The issues in RPC are:
i. How are the servers functions located and started?
ii. How are parameters defined and passed between the client and the server?
iii. How are failures handled?
iv. How is security handled by RPC?
v. How does the client find its server?
vi. How is data representation across systems handled?
5. Explain about Message Oriented Middleware and comparing MOM and RPC.
1. Explain RPC and MOM
2. Comparison table
· Features
· Metaphor
· Client/server relationship
· Client/server sequencing