Summary of "Lec-4: Client Server Architecture"
Brief summary
The video lecture covers distributed computing paradigms with a focus on the client–server architecture. It explains what client–server systems are, how clients and servers interact, how conceptual layers map to physical deployment (two‑tier vs three‑tier / multi‑tier), and the benefits and drawbacks of these designs. A single‑branch banking example (SBI) is used to illustrate the model.
Main ideas and concepts
Client–server architecture
- A classic distributed computing style with distinct client and server components connected over a network (historically a LAN).
- Server: typically a higher‑end machine where the application is developed, tested and deployed.
- Client: a lower‑configuration machine (or equivalently configured) used by end users to send requests and receive responses.
- Example topology: one server running the banking application and multiple client counters (C1, C2, C3) accessing it.
Communication pattern
- Request–response interaction: the client issues a request; the server processes it and returns a response.
- Characterized as a one‑time/unidirectional exchange (client → server → client), unlike simultaneous multi‑party chat tools (e.g., WhatsApp).
Core operations (roles)
- Client side: issue request.
- Server side:
- listen for requests,
- accept incoming requests,
- process and respond (return result).
Conceptual layers (tiers)
- Presentation (front end / view): user interface shown on the client.
- Application logic (business logic / model/controller): processes requests and mediates between presentation and data.
- Data storage: persistent storage for application data.
- Mapping to MVC: View = presentation; Model = application logic; Controller = controller logic.
Two‑tier vs three‑tier (and multi‑tier)
- Two‑tier:
- Client holds presentation.
- Server holds both application logic and data storage.
- Simple to implement but limited in scalability and fault tolerance.
- Three‑tier:
- Presentation, application logic, and data storage are separated onto different machines/nodes.
- More scalable because tiers can be distributed or replicated independently.
- Multi‑tier (n‑tier):
- Further division of stages/layers as needed to isolate bottlenecks and improve scalability and maintainability.
Suitability, advantages and limitations
When two‑tier is appropriate
- Suitable for small or limited systems with modest scalability requirements.
Major drawbacks of single‑server client–server deployments
- Single point of failure: if the server crashes, all clients are affected.
- Server overload: many concurrent clients can overwhelm the server.
- Scalability limitations: hard to scale as demand grows.
- Higher cost: server hardware and maintenance can be expensive.
- Maintenance downtime: updating or fixing server‑side code often requires stopping the server, testing and redeploying, during which clients cannot access the service.
- Example: fixing a bug in a single 10,000‑line program forces downtime and shows a “server is down” message to users.
Practical / operational sequences
Client request cycle (checklist)
- Client issues request.
- Server listens for incoming requests.
- Server accepts the request when received.
- Server processes the request (runs application logic, accesses data as needed).
- Server returns a response to the client.
Maintenance / update of a single‑server system (checklist)
- Stop the server/process.
- Edit/fix the server code (e.g., debug a large codebase).
- Test the changes.
- Deploy the fixed code to the server.
- Restart the server so clients can reconnect.
Example
Single-branch bank (SBI) example: one server runs the banking application and multiple client counters (C1, C2, C3) connect to it to perform transactions. This illustrates both the request–response interaction and the limitations (single point of failure, scalability constraints).
Speaker / source
- Lecturer / Instructor (unnamed) — presenting Lec‑4: Client Server Architecture.
Category
Educational
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