Overview of Web Protocols

Criteria for Web Protocol Selection • How constrained are the devices? • Reliable/unreliable network? • What is the message rate? • How is the data processed further? • Push or Pull? • What are security requirements? • What is the response time required?

MQTT – Message Queuing Telemetry Transport

Lightweight broker-based publish/subscribe messaging protocol designed to be open, simple, lightweight and easy to implement

• Ideal when

  • –  Network is expensive, has low bandwidth or is unreliable

  • –  Run on an embedded device with limited processor or memory resources


  • –  The publish/subscribe message pattern to provide one-to-many message

  • –  Distribution and decoupling of applications

  • –  A messaging transport that is agnostic to the content of the payload

  • –  The use of TCP/IP to provide basic network connectivity

  • –  Three qualities of service for message delivery

  • –  A small transport overhead - the fixed- length header is just 2 bytes 

MQTT Benefits 

Improved User Experience

  • Near real-time push of information 

  • Minimal battery usage

  • Store and forward messaging 

  • Exactly once delivery (where required) 

    Flexibility and Scalability

    Single server can support a million 
    connected users or devices as it’s event-

    Additional functionality can be easily integrated without changing existing code due to Publish/Subscribe architecture

    Lower Running Costs

    Very compact wire format, results in lower network costs
    Lightweight footprint – protocol will run on low power devices 

    Very low battery usage compared to HTTP 

    Lower Development Costs

    Recovery, store and forward, and publish/subscribe are provided by the MQTT implementations,

    and don't have to be coded into application logic. 

    Simple set of verbs, easy for developers to learn. 

    Easy integration with System of Records

    CoAP – Constrained Application Protocol

    CoAP is a specialized web transfer protocol for use with constrained nodes and constrained (e.g., low-power, lossy) networks.

    • Ideal when

    – Constrained nodes (e.g., 8-bit microcontrollers with limited RAM and ROM) such as wireless sensor networks (WSNs) requiring very low overhead

    • Key Features

    • –  Web protocol fulfilling M2M requirements in constrained environments

    • –  UDP [RFC0768] binding with optional reliability supporting unicast and multicast requests.

    • –  Asynchronous message exchanges

    • –  Low header overhead and parsing complexity

    • –  Uniform resource identifier (URI) and content-type support

    • –  Simple proxy and caching capabilities

    • –  Security binding to Datagram Transport Layer Security (DTLS) 

      CoAP Benefits

      • Open IETF standard

      • Low overhead and an excellent choice in constraints applications

      • Works well in noisy & lossy environments

      • Built-in discovery

      • Strong DTLS security

      • Asynchronous subscription 

        XMPP – Extensible Messaging and Presence Protocol

        XMPP is an open instant messaging protocol usually implemented via a client- server architecture wherein a client utilizing XMPP accesses a server over a TCP connection, and servers also communicate with each other over TCP connections

        • Ideal when

        – Connecting devices to people. For example, connecting home thermostat to a web server so data can be accessed over a phone
      • • Key Features
        • –  End to end communication between any peer. With name@domain.com addressing scheme, it enables connections between distant, mostly unrelated end points

        • –  Transport with end nodes can be of any type (IP, ZigBee, Bluetooth...)

        • –  XML based - easily extensible with arbitrary payloads. Distributed network of “web services”

        • –  Security: Very robust with Encryption, client authentication, & client authorization mandatory

        • –  Near real-time communication 

          XMPP Extension Protocols (XEP) for IoT

          Provides the underlying architecture, basic operations and data structures for sensor data communication over XMPP networks 

          XMPP Benefits

          • Real time messaging at massive scale – 100,000+ nodes

          • Secure – XMPP server may be isolated from the public network and robust security using SASL and TSL are built into the core
          • • Open – XMPP protocols are free, open, public and have been widely adopted

          • • Decentralized – the architecture of the XMPP network is similar to email – anyone can run their own XMPP server 

            Data Distribution Service (DDS)

            The first open international middleware standard directly addressing publish-subscribe communications for real-time and embedded


          • • Ideal for

            – Real time, secure communications between devices

            • Key Features

            • –  DDS is decentralized – can be deployed without servers and brokers

            • –  Publish/subscribe architecture

            • –  Scalable performance

              • Millions of data elements

              • .5m updates/sec

              • 10us latency

              • 1000s consumers/update

            • –  Managed with QoS

            • –  Reliable - no single point of failure

            • –  Built in detecting presence of applications 

              DDS Protocol Benefits

              • Platform neutral: Operating systems and Programming Languages

              • Delivers flexibility, reliability and performance necessary for complex, real- time applications

              • Real-time Quality of Service (QoS) control

              • Decentralized architecture allows for frequent observation of changes & uses network resources efficiently

              • Dynamic discovery of publishers and subscribers 

                AMQP – Advanced Messaging Queuing Protocol

                The Advanced Message Queuing Protocol (AMQP) is an open internet protocol for business messaging. It defines a binary wire-level protocol that allows for the reliable exchange of business messages between two parties

                • Ideal for

                – Connecting various enterprise systems in the enterprise and providing business processes with the information they need

                • Key Features

                • –  Multiple messaging related features - Reliable queuing, topic- based publish and subscribe, flexible routing, etc

                • –  Session and transactional message transfer

                • –  Efficient – packet size 60 bytes

                • –  Security – SSL/TLS, SASL

                • –  Quality of Service – best effort, at least once, exactly once 

                  • All AMQP clients interoperate with all AMQP servers

                  • Diverse programming languages can communicate easily

                  • Legacy message brokers can be retrofitted to remove proprietary protocols

                  • Enables messaging as a cloud service 

                  AMQP Benefits

                  • Flexible, open and interoperable. AMQP can connect across organizations and technologies while guaranteeing QoS and security

                  – Realize the savings commoditization brings; remove vendor lock-in
                • – Connect applications on different platforms; choose the right platform for the job
                  • –  Connect to business partners using a full featured open standard; remove technical barriers to trade

                  • –  Reliability operate at a distance, or over poor networks 





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