DSYS
What is a distributed system? - ANSWER A distributed system is a
collection of independent computers that appears to its users as a single
coherent system
What are the motivations for distributed systems? - ANSWER Because
the world is distributed.
Because joining forces increases performance and availability.
Because problems rarely hit two different places at the same time. As a
company having only one database server is a bad idea.
What is Middleware? - ANSWER Middleware is the software that
connects software components or enterprise applications. Middleware is
the software layer that lies between the operating system and the
applications on each side of a distributed computer network.
Typically, it supports complex, distributed business software
applications.
Provides abstraction and hides complexity.
Name the goals of middleware. [TO REDS] - ANSWER Transparency
- The ability to view a distributed system as if it were a single computer
- Varying dimensions of transparency incl. location, access, migration,
etc.
- The degree of transparency is a key decision in any systems
architecture
Openness
- The offering of services according to standard rules (syntax and
semantics)
, - Openness provides support for the key properties of portability and
interoperability
- Again, the degree of openness is a key factor in systems design
Resource sharing
- The ability to access and share resources in a distributed environment
- The bread and butter of distributed systems
Extensibility
- The ability to be able to introduce new or modified functionality
Dependability/ Quality of Service
- Security
- Providing secure and authenticated channels, access control, key
management, etc.
- Fault-tolerance
- Providing highly available and resilient distributed applications and
services
Scalability
- Scalable with respect to size, e.g. support massive growth in the
number of users of a service
- Scalable with respect to geography, e.g. supporting distributed systems
that span continents (dealing with latencies, etc)
- Scalable with respect to administration, e.g. supporting systems which
span many diferent administrative organisations
What are the three different ways to protect against security threats? -
ANSWER Sandboxing, encryption, authentication
How can we ensure protection against malicious mobile code? -
ANSWER Sandboxing
How can we ensure secure communication? - ANSWER Encryption
How can we ensure access control? - ANSWER Authentication
What is a distributed system? - ANSWER A distributed system is a
collection of independent computers that appears to its users as a single
coherent system
What are the motivations for distributed systems? - ANSWER Because
the world is distributed.
Because joining forces increases performance and availability.
Because problems rarely hit two different places at the same time. As a
company having only one database server is a bad idea.
What is Middleware? - ANSWER Middleware is the software that
connects software components or enterprise applications. Middleware is
the software layer that lies between the operating system and the
applications on each side of a distributed computer network.
Typically, it supports complex, distributed business software
applications.
Provides abstraction and hides complexity.
Name the goals of middleware. [TO REDS] - ANSWER Transparency
- The ability to view a distributed system as if it were a single computer
- Varying dimensions of transparency incl. location, access, migration,
etc.
- The degree of transparency is a key decision in any systems
architecture
Openness
- The offering of services according to standard rules (syntax and
semantics)
, - Openness provides support for the key properties of portability and
interoperability
- Again, the degree of openness is a key factor in systems design
Resource sharing
- The ability to access and share resources in a distributed environment
- The bread and butter of distributed systems
Extensibility
- The ability to be able to introduce new or modified functionality
Dependability/ Quality of Service
- Security
- Providing secure and authenticated channels, access control, key
management, etc.
- Fault-tolerance
- Providing highly available and resilient distributed applications and
services
Scalability
- Scalable with respect to size, e.g. support massive growth in the
number of users of a service
- Scalable with respect to geography, e.g. supporting distributed systems
that span continents (dealing with latencies, etc)
- Scalable with respect to administration, e.g. supporting systems which
span many diferent administrative organisations
What are the three different ways to protect against security threats? -
ANSWER Sandboxing, encryption, authentication
How can we ensure protection against malicious mobile code? -
ANSWER Sandboxing
How can we ensure secure communication? - ANSWER Encryption
How can we ensure access control? - ANSWER Authentication
