System Design: TCP and UDP

TCP

Transmission Control Protocol (TCP) is connection-oriented, meaning once a connection has been established, data can be transmitted in both directions. TCP has built-in systems to check for errors and to guarantee data will be delivered in the order it was sent, making it the perfect protocol for transferring information like still images, data files, and web pages.

But while TCP is instinctively reliable, its feedback mechanisms also result in a larger overhead, translating to greater use of the available bandwidth on the network.

UDP

User Datagram Protocol (UDP) is a simpler, connectionless internet protocol in which error-checking and recovery services are not required. With UDP, there is no overhead for opening a connection, maintaining a connection, or terminating a connection. Data is continuously sent to the recipient, whether or not they receive it.

It is largely preferred for real-time communications like broadcast or multicast network transmission. We should use UDP over TCP when we need the lowest latency and late data is worse than the loss of data.

TCP vs UDP

TCP is a connection-oriented protocol, whereas UDP is a connectionless protocol. A key difference between TCP and UDP is speed, as TCP is comparatively slower than UDP. Overall, UDP is a much faster, simpler, and more efficient protocol, however, retransmission of lost data packets is only possible with TCP.

TCP provides ordered delivery of data from user to server (and vice versa), whereas UDP is not dedicated to end-to-end communications, nor does it check the readiness of the receiver.

Feature	TCP	UDP
Connection	Requires an established connection	Connectionless protocol
Guaranteed delivery	Can guarantee delivery of data	Cannot guarantee delivery of data
Re-transmission	Re-transmission of lost packets is possible	No re-transmission of lost packets
Speed	Slower than UDP	Faster than TCP
Broadcasting	Does not support broadcasting	Supports broadcasting
Use cases	HTTPS, HTTP, SMTP, POP, FTP, etc	Video streaming, DNS, VoIP, etc

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Table of contents

• Getting Started

  • What is system design?

• Chapter I

  • IP
  • OSI Model
  • TCP and UDP
  • Domain Name System (DNS)
  • Load Balancing
  • Clustering
  • Caching
  • Content Delivery Network (CDN)
  • Proxy
  • Availability
  • Scalability
  • Storage

• Chapter II

  • Databases and DBMS
  • SQL databases
  • NoSQL databases
  • SQL vs NoSQL databases
  • Database Replication
  • Indexes
  • Normalization and Denormalization
  • ACID and BASE consistency models
  • CAP theorem
  • PACELC Theorem
  • Transactions
  • Distributed Transactions
  • Sharding
  • Consistent Hashing
  • Database Federation

• Chapter III

  • N-tier architecture
  • Message Brokers
  • Message Queues
  • Publish-Subscribe
  • Enterprise Service Bus (ESB)
  • Monoliths and Microservices
  • Event-Driven Architecture (EDA)
  • Event Sourcing
  • Command and Query Responsibility Segregation (CQRS)
  • API Gateway
  • REST, GraphQL, gRPC
  • Long polling, WebSockets, Server-Sent Events (SSE)

• Chapter IV

  • …

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