Distributed Systems Ryan Chris Van Kevin

Kinds of Systems Distributed Operating System –Offers Transparent View of Network –Controls multiprocessors and multicomputers Network Operating System –Specifically Written To Run Networks –Joins together many computers that each have their own operating system and allows them to share resources –Used for Local Area and Wide Area Networks

Internet vs. Intranet Internet –Public Network of Networks –Easily Accessible Through an ISP Intranet –Local and Private –Much Faster and Secure –Contained Within a Company or Business

Issues Relating To D.S. Transparency –Hides “Behind The Scenes” Activities Scalability –Whether or not a system can grow without loss of performance Software Interfaces –A distributed system can have many different types/brands of computers with different operating systems Security –Risks of security can arise from internal or external affairs in a distributed system

Packets Packets are fundamental units of information carriage used in computer networks A packet consists of three elements: Header, Data Area, and Trailer A datagram is a packet that can be sent independently of any connection setup

Protocol A standard that controls or enables the connection, communication, and data transfer between two computer endpoints Most recognizable protocol is the Internet protocol known as TCP/IP

Sockets There are two types of sockets: –Internet –IPC (Inter-Process Communication) IPC can be used in computing networking to create one end of a bi-directional link between two programs Defined as a combo of an IP address, a protocol, and a port number

Endpoints and Ports Endpoint is one end of a connection Some ports are: –Hardware –Software –Network

RPC Short for Remote Procedure Call Popular paradigm for implementing the client/server model of distributed computing Operates over UDP or TCP Client can execute a program on a server Client sends arguments to the server Encodes data by using XDR Protocol

Middleware Software that connects 2 separate applications Called a Conversion or Transition layer 1 st Middleware Product – Teleprocessing Monitor Need for middleware increases as IT becomes more complex Makes application development easier

Client/Server Model Term first used back in the 80’s One of the more important ideas in networking Common example is TCP/IP Client makes a request from the server, then the server sends back the fulfilled request Server is sometimes called a daemon Example – Internet Browser

Security Threats Interception –An unauthorized party that gains access to an asset. –Example: An unauthorized party eavesdropping on what you are doing, but not tampering with anything. Interruption –An asset of a system is destroyed, unavailable or unusable. –Example: An unauthorized party deleting a program so you can not use it.

Security Threats Modification –An unauthorized party gains access as well as tampers with assets. –Example: An unauthorized user modifying files on your computer Fabrication –An unauthorized party inserts fake objects into the system –Example: An unauthorized user adds a new file onto your computer.

Security Mechanisms Encryption  Encryption is the coding or scrambling of information so that it can be decoded and read by someone who has the correct decoding key.  Used to secure Web sites as well as other mediums of data transfer.  If a third party were to intercept the information you sent via an encrypted connection, they would not be able to read it.  Two Types  Symmetric  Requires only one key to encrypt and decrypt  Asymmetric  Requires two keys, one to encrypt and one to decrypt

Security Mechanisms Authentication Authentication is any process by which a system verifies the identity of a user who wishes to access it –Example Credentials (username and password) Authorization Authorization grants users access to different areas on a system based on their identity –Example User groups (Admin, User, Guest etc.)

Security Mechanisms Auditing –An independent review and examination of data processing, system records and activities. –Used to… Test for adequacy of system controls Ensure compliance with established security policy and operational procedures Detect breaches in security Recommend any indicated changes in control, security policy, and procedures

Client-Server Model Example – A client requests a web page from a server, the server then returns the website to the client