Tags:conceptcomputernetworksnetworkosimodel Status:🟩
Computer Networks
Summary
Computer networks are fundamental to distributed systems, enabling communication between processes running on different hosts. A network allows systems to share resources, coordinate actions, and ensure data exchange, but also introduces challenges such as heterogeneity, security concerns, and failures.
Foundations of Networking
Basis model
- Hosts can include various devices such as laptops, servers, and other computing devices.
- Processes operate on these hosts, executing tasks and services.
- Communication between processes occurs through messages sent and received over designated communication channels.
- Both processes and communication channels are susceptible to failures, impacting the reliability and efficiency of the distributed system.
Failures
- Channel failures can result in issues such as dropped, lost, reordered, or duplicated messages.
- Channels can also experience two types of failures:
- Omission failures: When a channel fails to send a message that should have been sent.
- Byzantine failures: When a channel behaves unpredictably, possibly sending incorrect or misleading messages.
Security
An attacker can perform various malicious actions on messages, including:
- Intercepting messages
- Copying messages
- Modifying or transforming messages
- Inserting new messages
- Deleting existing messages
Channel failure handling
Various strategies are employed to handle different types of channel failures:
- Message Corruption: Checksums help verify that messages have not been altered during transmission, ensuring data integrity.
- Lost Messages: Mechanisms like acknowledgments, timeouts, and retransmissions ensure that messages that fail to reach their destination are resent, maintaining communication flow.
- Duplicated or Reordered Messages: Sequence numbers are used to track the order of messages, helping to identify and manage duplicates and ensuring that messages are processed in the correct sequence.
- Security: Cryptography and secure protocols safeguard messages against unauthorized access and alterations, ensuring the confidentiality and integrity of data.
Open System Interconnection (OSI) Model
 |  |
|---|---|
| The Open Systems Interconnection (OSI) Model provides a framework for understanding how different protocols interact and work together in a layered approach. | |
| The physical layer could be a wireless connection, fiber connection or a wired connection. | |
| OSI Model - Network Layer | |
| OSI Model - Transport Layer | |
| OSI Model - Application layer |
Protocols in Networking
- Processes and Protocols: Processes in distributed systems adhere to protocols, which are defined sequences of message exchanges and data formats. These protocols ensure standardized communication between processes.
- Examples of Protocols: Common protocols include TCP (Transmission Control Protocol), UDP (User Datagram Protocol), SMTP (Simple Mail Transfer Protocol), and HTTP (Hypertext Transfer Protocol).
- Protocol Stacks: Protocols are often organized in stacks, where each layer adds specific functionality. Each layer communicates with the layers directly above and below it, allowing for modular and flexible networking.