N12. Application paradigms

Question 1

Describe peer-to-peer paradigm

Answer 1

- Symmetric model of operation
(all nodes/hosts do same thing)
All nodes:
- can be clients
- can be servers
- can initiate communication
- can respond to communication
- may perform processing on resources even when no communication is taking place 
(resources are distributed not centralised)

Question 2

Describe client-server paradigm

Answer 2

• Asymmetric model of operation
  (client and server do different things)
  Server provides access to resources (passive but responsive)
  Client sends requests to server (control operation of application - client actions progress session with the app)
  Consumption - client does most computation on resources

Question 3

Give an overview of peer-to-peer protocol

Answer 3

Data-transfer protocol (user-plane)
(file found: transfer between peers)
Discovery protocol (control-plane)
- discover resources (distributed search)
- resources and nodes can be added/removed
Unstructured - no relationships (random connections between nodes)
Structured - specific topology/structure
(e.g. distributed hash table)

Question 4

Describe the publish-subscribe (pub-sub) paradigm

Answer 4

Senders = publishers
(produce channels of categorised info)
Receivers/consumers = subscribers
(select info channels based on category - items might be filtered by subscriber)
Publishers and subscribers do not need to be aware of each other’s communication (no need to connect)

Question 5

Give some applications of pub-sub

Answer 5

• Messages “buses”
• Real-time data streams
• Notification services
• Internet of Things

Question 6

Data (re)presentation formats

Answer 6

General problem - data structure as byte stream (data serialisation)
text-based protocols, binary formats, JSON