



Network Working Group                                           S. Dutta
Internet-Draft                                               Independent
Intended status: Standards Track                       16 September 2025
Expires: 20 March 2026


               SIME: Srijal's Integrated Mail Extensions
                     draft-srijal-sime-protocol-00

Abstract

   This document specifies the SIME protocol, a decentralized, atomic
   protocol for inter-domain mail transmission and entity-to-entity
   communication.  It defines packet types, headers, MX/SRV-based trust
   verification, TCP-based delivery, and SIME Extensions for
   attachments.  All servers act as Domain Authorities (DA), and inter-
   domain transactions are governed by atomic protocol rules.

Status of This Memo

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   This Internet-Draft will expire on 20 March 2026.

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   provided without warranty as described in the Revised BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Overview of SIME Protocol . . . . . . . . . . . . . . . . . .   3
   4.  Packet Types  . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Headers . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   6.  Authentication and Login  . . . . . . . . . . . . . . . . . .   4
   7.  Message Flow  . . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Atomic Protocol Rules . . . . . . . . . . . . . . . . . . . .   4
   9.  Inter-Domain Transactions . . . . . . . . . . . . . . . . . .   5
   10. Error Codes . . . . . . . . . . . . . . . . . . . . . . . . .   5
   11. Security Considerations . . . . . . . . . . . . . . . . . . .   5
   12. MX/SRV Verification . . . . . . . . . . . . . . . . . . . . .   5
   13. SIME Extensions for Attachments . . . . . . . . . . . . . . .   6
   14. Packet Syntax . . . . . . . . . . . . . . . . . . . . . . . .   6
   15. Example Message Flow  . . . . . . . . . . . . . . . . . . . .   6
   16. Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Appendix A.  Authors' Addresses . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   SIME (Srijal's Integrated Mail Extensions) is a decentralized
   protocol designed to provide reliable messaging between users in
   different Domain Authorities (DA).  Each DA manages its own user
   authentication and registration rules.  Atomic protocol enforcement
   ensures inter-domain transactions follow strict compatibility,
   reliability, and security rules.

   All SIME traffic is conducted over TCP to ensure reliable delivery.

2.  Terminology

   DA (Domain Authority) - Server managing a domain and its users

   ID - Disposable session identifier (e.g., JWT)

   Transaction ID - Identifier assigned per transaction session

   TCP - Transmission Control Protocol (mandatory transport)

   MAIL Packet - Packet containing mail messages

   CONV Packet - Packet for general communication

   MX/SRV Record - DNS record or SRV record pointing to server endpoint
   for inter-domain verification



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3.  Overview of SIME Protocol

   - Users authenticate with their DA and receive disposable IDs.

   - Communication is TCP-only to prevent packet loss.

   - Two primary packet types: CONV and MAIL.

   - Inter-domain transactions require MX/SRV verification to ensure
   messages reach the correct DA server.

   - Atomic rules enforce uniformity; non-compliant servers are
   rejected.

4.  Packet Types

   CONV Packets:

   Used for login and general communications:

   LOGIN <username> <password>
   START TRANSACTION <ID>
   CONV <payload>

                                  Figure 1

   MAIL Packets:

   Used for sending messages:

PREPARE HEADERS <transact_id> X-Mailed-Type-Render: <TXT|MD|HTML>; RECIPIENT: user@domain
PREPARE MESSAGE <transact_id> <content>
END TRANSACTION <transact_id>

                               Figure 2

5.  Headers

   - SENDER: Originating user (user@domain)

   - RECIPIENT: Destination user (user@domain)

   - X-Mailed-Type-Render: TXT | MD | HTML

   - Optional headers may be added via SIME Extensions






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6.  Authentication and Login

   Users initiate login via CONV packet:

   LOGIN <username> <password>

                                  Figure 3

   Server responses:

   SUCCESS LOGIN : <ID>
   ERROR AUTH

                                  Figure 4

   Disposable IDs are required for subsequent packets.

7.  Message Flow

   1.  User logs in: CONV Packet → LOGIN → SUCCESS LOGIN : <ID>

   2.  User initiates transaction: CONV Packet → START TRANSACTION <ID>

   3.  Server validates ID:

   - Success → returns transaction acknowledgment

   - Failure → returns ERROR AUTH

   4.  User sends MAIL packet:

   - PREPARE HEADERS <transact_id> ...

   - PREPARE MESSAGE <transact_id> <content>

   5.  User ends transaction: END TRANSACTION <transact_id>

   6.  Server responds with SENT or appropriate error.

8.  Atomic Protocol Rules

   - No version negotiation; all inter-domain servers must implement the
   exact protocol.

   - Non-compliant servers are rejected.

   - Transactions must be atomic: either all steps succeed or fail.




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9.  Inter-Domain Transactions

   - DA MX/SRV record must point to verified server endpoint.

   - Messages are sent only to verified MX/SRV endpoints.

   - Servers not listed or failing verification are rejected.

10.  Error Codes

   - ERROR AUTH : Invalid login/session

   - ERROR TRANS : Transaction initiation failure

   - ERROR HEADER : Invalid or missing headers

   - ERROR MXVER : Inter-domain MX/SRV verification failure

   - ERROR PACKET : Malformed packet

   - ERROR SEND : Message could not be delivered

11.  Security Considerations

   - All packets use TCP for reliable delivery.

   - Authentication handled per DA; disposable IDs required.

   - TLS is recommended for inter-domain traffic.

   - Disposable IDs and transaction IDs mitigate replay attacks.

   - Inter-domain trust relies on MX/SRV verification; unverified
   endpoints are rejected.

   - Confidentiality and integrity of message content require TLS or
   optional message signing.

   - Reviewers should note that deployment must account for standard-
   compliant DNS/SRV usage instead of arbitrary IP:PORT MX records.

12.  MX/SRV Verification

   - Each DA must publish a SIME MX or SRV record specifying its server
   endpoint.

   - Inter-domain messages are routed only to verified endpoints.




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   - Unverified endpoints are rejected.

13.  SIME Extensions for Attachments

   - ATTACHMENT: <filename>

   - ENCODING: base64 | hex

   - Optional metadata headers supported

   - Attached in content as: <UNICODE UTF-8: 0xEF 0xBF 0xBF><hex|base64>
   <encoded attachment><UNICODE UTF-8: 0xEF 0xBF 0xBF>

14.  Packet Syntax

CONV-PACKET   = LOGIN-PACKET / TRANSACTION-PACKET / GENERAL-CONV
LOGIN-PACKET  = "LOGIN" SP USERNAME SP PASSWORD CRLF
TRANSACTION-PACKET = "START TRANSACTION" SP ID CRLF / CONV SP PAYLOAD CRLF
MAIL-PACKET  = "PREPARE HEADERS" SP TRANSACTION-ID SP HEADER-FIELDS CRLF
               "PREPARE MESSAGE" SP TRANSACTION-ID SP CONTENT CRLF
               "END TRANSACTION" SP TRANSACTION-ID CRLF

USERNAME     = 1*(ALPHA / DIGIT / "-" / "_")
PASSWORD     = 1*(ALPHA / DIGIT / SYMBOL)
TRANSACTION-ID = 1*DIGIT
HEADER-FIELDS = *(HEADER-NAME ":" SP HEADER-VALUE CRLF)
CONTENT      = *(OCTET)

                               Figure 5

15.  Example Message Flow

   User                 DA-A                 DA-B
    | LOGIN             |                     |
    |------------------>| SUCCESS LOGIN      |
    | START TRANSACTION |                     |
    |------------------>| TRANS_ID: 67890    |
    | PREPARE HEADERS   |                     |
    |------------------>| PROCEED             |
    | PREPARE MESSAGE   |                     |
    |------------------>| PROCEED             |
    | END TRANSACTION   |                     |
    |------------------>| SENT                |

                                  Figure 6

16.  Normative References




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   [RFC793]   Postel, J., "Transmission Control Protocol", RFC 793,
              1981, <https://www.rfc-editor.org/rfc/rfc793>.

   [RFC7519]  Jones, M., "JSON Web Token (JWT)", RFC 7519, 2015,
              <https://www.rfc-editor.org/rfc/rfc7519>.

   [RFC5321]  Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
              2008, <https://www.rfc-editor.org/rfc/rfc5321>.

Appendix A.  Authors' Addresses

   Srijal Dutta

   Email: srijaldutta.official+sime@gmail.com

Author's Address

   Srijal Dutta
   Independent
   Email: srijaldutta.official+sime@gmail.com































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