Types of network protocols (A2.1 Network fundamentals)

Network protocol

Set of rules and standards defining how data should be structured, transmitted, received across network

• Determine format, timing, sequencing, error checking of data (were packets lost in transmission)

I. TYPES

Two types of network protocols

Stateful (I. TYPES)

Maintain state info/context about client-server session across multiple requests and responses

Stateless (I. TYPES)

DOESN’T maintain state info about sessions

• Each communication session treated as blank slate: independent and unrelated to prev ones

II. PROTOCOL EXAMPLES

Most commonly known protocols used

Transmission Control Protocol (TCP) (II)

Reliable, ordered, error-checked delivery of stream of bytes between hosts communicate w/ IP network

• STATEFUL

• CORE protocol of the internet

• Operates at transport layer of TCP model

• Guarantees delivery of data

• Key features:

  • Handshake process - connection-oriented protocol: connection between devices must be established before transmission

  • Acknowledge data transfer

  • Flow control (prevent network congestion) 

  • Connection termination

• Guarantees delivery of data = used where data integrity and delivery order of packets are important

User datagram protocol (UDP) (II)

Data packets/datagrams sent between devices W/O establishing stateful connection between communication endpoints (CONNECTIONLESS)

• STATELESS

• Aka Fire and forget protocol

• Key features

  • Faster,  v resource-intensive than TCP (no overhead needed with setting up, maintaining connection)

  • Also supports Multicasting - transmission of packet to multiple destinations in single send operation

• DOES NOT guarantee delivery of data = Good where occasional data loss is tolerable (eg video streaming) and speed is prioritized

HyperText transfer protocol (HTTP) (II)

Transmission of hypermedia documents (HTML, Javascript, CSS, binary, etc)

• STATELESS

• Foundation of WWW

• Through unicode text strings (human-readable)

• Request/response model - input sends request, HTTP responds

  • Ex: request reload page, responds by reloading page 

• Cookie - file stored in client’s device which store state info

  • Sent with requests to enable stateful communication (to aid stateless HTTP)

  • Stored in DEVICE not in PROTOCOL

• Session - allow server to maintain user-specific data across multiple HTTP requests

  • Eg if logged in, what last looked at in online store, time zone

HyperText transfer protocol secure (HTTPS) (II)

Extension of HTTP: enhanced security for communications over WWW

• Encryption

• Authentication

• Data integrity

• HTTPS(/SSL/TLS) certificate - verifies website’s identity, enables encrypted connection

  • Security through transport layer security (TLS) protocol

    • Formerly through predecessor: secure sockets layer (SSL)

Dynamic host configuration protocol (DHCP) (II)

Process where computer requests and receives valid IP address for use on that network

• STATEFUL

• Most common: used when computer first joins computer network

• Methods of allocating IP addresses:

  • Dynamic allocation - IP address assigned to device for limited period: lease

  • Static allocation - IP assigned PERMANENTLY to device based on MAC address

    • Usually for sharing resources: printer, server, etc

• Subnet mask - 32 bit numbers divides IP address into network and host portions

  • Determines which part of IP address refers to network, which to host

  • Same network = same subnet mask (first 6 digits of IP address the same)

III. Transmission control protocol/Internet protocol model (TCP/IP)

Conceptual approach to understanding roles and responsibilities of networking communication

• Uses 4 layers from OSI model

• Layers:

  • Application layer - using and correctly forming messages

    • Very visible to end user

  • Transport layer - receives data from application layer, segments, error detects and correction

    • Indicates what specific protocol is uses

  • Internet layer - manage how packets are sent across network

  • Network interface layer - physical transmission of data across networking hardware and transmission media

    • Physical interface: actual hardware