Protocols and Models

• Communications Protocols

  • All communications are governed by protocols
  • Protocols are the rules that communications will follow
  • Rules will vary depending on the protocol
• Network Protocol Requirements

  Common computer protocols must be in agreement and include message encoding, message formatting and encapsulation, message size, message timing, message delivery options
• Message Timing

  • Includes flow control, response timeout, access method, and rules governing issues like collisions
• Devices must agree on "how" to communicate
• Message Formatting and Encapsulation

  • Messages must use a specific format or structure depending on the type of message and the channel used
• Elements of communication

  • Source (sender)
  • Destination (receiver)
  • Channel (media)
• Rule Establishment

  1. Individuals must use established rules or agreements to govern the conversation

  2. Protocols must account for identified sender and receiver, common language and grammar, speed and timing of delivery, confirmation or acknowledgment requirements
• Networks

  • Can vary in size and complexity
• Message Encoding

  • Process of converting information into another acceptable form for transmission
• Message Size

  • Messages sent across the network are converted to bits, encoded into a pattern of light, sound, or electrical impulses, and decoded by the destination host
• Some protocols are proactive and attempt to prevent collisions; other protocols are reactive and establish a recovery method after the collision occurs
• Documents may use the node icon, typically a circle, to represent all devices
• Protocol Type

  • Network Communications
  • Network Security
  • Routing
  • Service Discovery
• Message delivery options

  • Unicast - one to one communication
  • Multicast - one to many, typically not all
  • Broadcast - one to all
• Protocol Functions

  • Addressing - Identifies sender and receiver
  • Reliability - Provides guaranteed delivery
  • Flow Control - Ensures data flows at an efficient rate
  • Sequencing - Uniquely labels each transmitted segment of data
  • Error Detection - Determines if data became corrupted during transmission
  • Application Interface - Process-to-process communications between network applications
• TCP/IP is the protocol suite used by the internet and includes many protocols
• Evolution of Protocol Suites

  • Internet Protocol Suite or TCP/IP
  • Open Systems Interconnection (OSI) protocols
  • AppleTalk
  • Novell NetWare
• Protocol Interaction

  • Hypertext Transfer Protocol (HTTP)
  • Transmission Control Protocol (TCP)
  • Internet Protocol (IP)
  • Ethernet
• Network protocols define a common set of rules and can be implemented on devices in software, hardware, or both
• Networks require the use of several protocols, each with its own function and format
• TCP/IP protocols operate at the application, transport, and internet layers, with the most common network access layer LAN protocols being Ethernet and WLAN (wireless LAN)
• Devices use agreed-upon protocols to communicate and protocols may have one or more functions
• Message delivery options may be one of the following methods:
• Protocols must be able to work with other protocols and are viewed in terms of layers: Higher Layers and Lower Layers
• One device sends traffic at the same time and the messages become corrupt
• Broadcasts are used in IPv4 networks, but are not an option for IPv6. Later we will also see “Anycast” as an additional delivery option for IPv6
• Complex concepts such as how a network operates can be difficult to explain and understand, hence a layered model is used
• Two layered models describing network operations

  • Open System Interconnection (OSI) Reference Model
  • TCP/IP Reference Model
• Most common network access layer LAN protocols

  • Ethernet
  • WLAN (wireless LAN)
• TCP/IP Communication Process

  1. A web server encapsulating and sending a web page to a client

  2. A client de-encapsulating the web page for the web browser
• Standards organizations

  • Internet Society (ISOC)
  • Internet Architecture Board (IAB)
  • Internet Engineering Task Force (IETF)
  • Internet Research Task Force (IRTF)
  • Internet Corporation for Assigned Names and Numbers (ICANN)
  • Internet Assigned Numbers Authority (IANA)
  • Institute of Electrical and Electronics Engineers (IEEE)
  • Electronic Industries Alliance (EIA)
  • Telecommunications Industry Association (TIA)
  • International Telecommunications Union-Telecommunication Standardization Sector (ITU-T)
• Standards organizations involved with the development and support of TCP/IP

  • Internet Corporation for Assigned Names and Numbers (ICANN) coordinates IP address allocation, the management of domain names, and assignment of other information
  • Internet Assigned Numbers Authority (IANA) oversees and manages IP address allocation, domain name management, and protocol identifiers for ICANN
• Open standards encourage interoperability, competition, and innovation
• TCP/IP


  • Open standard protocol suite that is freely available to the public and can be used by any vendor
  • Standards-based protocol suite endorsed by the networking industry and approved by a standards organization to ensure interoperability
• Benefits of using a layered model

  • Assist in protocol design because protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below
  • Foster competition because products from different vendors can work together
  • Prevent technology or capability changes in one layer from affecting other layers above and below
  • Provide a common language to describe networking functions and capabilities
• Segmenting messages increases speed and efficiency
• TCP/IP Model Layer Internet

  Determines the best path through the network
• The TCP/IP protocol suite does not specify which protocols to use when transmitting over a physical medium
• OSI Model Layer 7 - Application

  Contains protocols used for process-to-process communications
• Provide a common language to describe networking functions and capabilities