The JSON Message Protocol
draft-ferg-jsmp-v0

Abstract

The JSON Message Protocol defines a bidirectional messaging protocol using JSON as a payload serialization format. Messages are typed and addressed. Both unidirectional messages and bidirectional queries are supported. JSMP is expected to be built on top of a framing protocol like WebSockets.

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Table of Contents

1.  Introduction
2.  Requirements
3.  Protocol Overview
4.  General Requirements
    4.1.  Requirements
    4.2.  Syntax Notation
    4.3.  Terminology
    4.4.  Basic Rules
5.  Packets
    5.1.  message
    5.2.  message-error
    5.3.  query
    5.4.  response
    5.5.  query-error
6.  Security Considerations
7.  Normative References
§  Author's Address
§  Intellectual Property and Copyright Statements

1.  Introduction

The goal of JSMP is to provide structure for a JSON-based messaging over a WebSockets connection.

JSON supports:

• typed messages, allowing for an object-oriented messaging style.
• addressable actors on the client and servers, enabling encapsulation of services.
• unidirectional messages and bidirectional query-response pairs for both major messaging styles.
• payloads encoded using JSON.

2.  Requirements

1. JSMP must support unidirectional messages.
2. JSMP must support query-response pairs.
3. JSMP responses may be unordered to the querires or messages.
4. JSMP must support typed messages.
5. JSMP must support services, using addresses for routing.

3.  Protocol Overview

This section is non-normative.

A unidirectional message looks as follows:

  message
  to@target.example.com
  from@source.example.com
  com.example.MyMessageType
  {"value", "my-payload-value"}

Bidirectional queries consist of a "query" packet and a corresponding "response" packet. The query and response are correlated with a correlation-id, which is a 64-bit integer.

A service MUST response to a "query" with either a "response" or a "query_error" because the client will be waiting for the response.

A query looks as follows:

  query
  to@target.example.com
  from@source.example.com
  com.example.MyQueryType
  12345
  {"value", "my-payload-value"}

The corresponding response looks as follows:

  response
  from@source.example.com
  to@target.example.com
  com.example.MyResponseType
  12345
  {"value", "my-payload-value"}

4.  General Requirements

4.1.  Requirements

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

An implementation is not compliant if it fails to satisfy one or more of the MUST or REQUIRED level requirements for the protocols it implements. An implementation that satisfies all the MUST or REQUIRED level and all the SHOULD level requirements for its protocols is said to be "unconditionally compliant"; one that satisfies all the MUST level requirements but not all the SHOULD level requirements for its protocols is said to be "conditionally compliant."

4.2.  Syntax Notation

This specification uses the Augmented Backus-Naur Form (ABNF) notation of [RFC5234] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” January 2008.).

The following core rules are included by reference, as defined in [RFC5234] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” January 2008.), Appendix B.1: ALPHA (letters), CR (carriage return), CRLF (CR LF), DIGIT (decimal 0-9), OCTET (any 8-bit sequence of data), SP (space), VCHAR (any visible [USASCII] character), and WSP (whitespace).

4.3.  Terminology

This specification the following JSMP

address: An address of a JSMP actor/service.

payload: A JSON value.

type: A string representing a message type.

4.4.  Basic Rules

The following basic rules follow the definitions in HTTP [RFC2616] (Fielding, R., Gettys, J., Mogul, J., Mainter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” June 1999.).

  token          = 1*tchar

  tchar          = "!" / "#" / "$" / "%" / "&" / "'" / "*"
                 / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
                 / DIGIT / ALPHA
                 ; any VCHAR, except special

  type_name      = 1* ( ALPHA / DIGIT / "_" / "." )

  correlation_id = 1* DIGIT

  payload        = JSON

  error_payload  = JSON

The following is the format of a JSMP address.

  address = [user '@'] domain [ '/' resource ]

5.  Packets

The following 5 packets are the only packets allowed for JSMP: message, message_error, query, response, query_error.

The stream consists of a sequence of packets.

  stream  = *( packet )

  packet  = message
            / message-error
            / query
            / response
            / query-error

5.1.  message

message is a unidirectional message.

message grammar

  message ::= "message" LF
              address LF
              address LF
              type LF
              payload LF

A unidirectional message looks as follows:

  message
  to@target.example.com
  from@source.example.com
  com.example.MyMessageType
  {"value", "my-payload-value"}

5.2.  message-error

message is an error response to a message.

message error grammar

  message_error ::= "message_error" LF
                   address LF
                   address LF
                   type LF
                   payload LF
                   error_payload LF

A unidirectional message looks as follows:

  message_error
  from@source.example.com
  to@target.example.com
  com.example.MyMessageType
  {"value", "my-payload-value"}
  {"code", "zomg"}

5.3.  query

query is a bidirectional request for a response. A receiver MUST response with either a "response" or a "queryError"

query grammar

  query ::= "query" LF
            address LF
            address LF
            type LF
            correlation_id LF
            payload LF

Example: A query looks as follows:

  query
  to@target.example.com
  from@source.example.com
  com.example.MyQueryType
  12345
  {"value", "my-payload-value"}

5.4.  response

"response" is a bidirectional response to a query.

response grammar

  response ::= "response" LF
               address LF
               address LF
               type LF
               correlation_id LF
               payload LF

Example: A response looks as follows:

  response
  to@target.example.com
  from@source.example.com
  com.example.MyQueryType
  12345
  {"value", "my-payload-value"}

5.5.  query-error

query-error is an error response to a message.

query-error grammar

  query_error ::= "query_error" LF
                   address LF
                   address LF
                   type LF
                   correlation_id LF
                   payload LF
                   error_payload LF

A unidirectional message looks as follows:

  messageError
  from@source.example.com
  to@target.example.com
  com.example.MyMessageType
  {"value", "my-payload-value"}
  {"code", "zomg"}

6.  Security Considerations

This section is meant to inform application developers and users of security issues related to JSMP. This list is unlikely to be complete.

7. Normative References

Author's Address

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