Secure Interactive Low-Latency Interactive Messaging (SLIM)

Internet-Draft	agent-slim	June 2025
Muscariello, et al.	Expires 7 December 2025	[Page]

Abstract

This document specifies the Secure Low-Latency Interactive RealTime Messaging (SLIM), a protocol designed to support real-time interactive AI applications at scale. SLIM leverates gRPC and add publish-subscribe capabilities to enable efficient many-to-many communication patterns between AI agentic applications (AI models, tools and data). The protocol provides mechanisms for connection management, stream multiplexing, and flow control while maintaining compatibility with existing gRPC deployments.¶

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶

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This Internet-Draft will expire on 7 December 2025.¶

2. Introduction

As AI systems become more sophisticated and interconnected, there is a growing need for protocols that can support real-time interactive applications at scale.¶

2.1. Protocol Overview

SLIM is designed to work as messaging layer for applications running as workloads in a data center, but also running in a browser or mobile device while guaranteeing end-end security and low-latency communication. SLIM leverages HTTP/2 end to end as a thin waist of the communication stack and avoids the need to create message transcoding along the path. By leveraging message encryption via MLS, TLS connection termination along the path does not negatively affect confidentiality. Authentication and authorization are handled at the application level and can be managed in a decentralized or federated way or a mix of both.¶

In SLIM there are three main communication elements: 1) intermediate nodes equipped with message queues, 2) message producers and 3) message consumers.¶

A producer (also called a "publisher") is an endpoint that encapsulates content in SLIM messages for transport within the SLIM message network of nodes. A producer MUST belong to an MLS group to encrypt messages that can be decrypted by message consumers who are members of the same group, as specified by the MLS protocol. Once a SLIM message is encrypted, it can be published under a routable name, which is human-readable and hierarchical. This routable channel name is used by intermediate nodes to store and forward messages within the same channel, allowing consumers to retrieve messages using this name.¶

A routable name is a name prefix that is stored in a forwarding table (FIB). This enables requests to reach the producer and fetch a response, if one exists. `¶

2.2. Terminology

3. Architecture

3.1. Protocol Layers

     +-------------------+
     |     Application   |
     +-------------------+
     |   SLIM Services    |
     +-------------------+
     |     Pub/Sub       |
     +-------------------+
     |      gRPC         |
     +-------------------+
     |      HTTP/2       |
     +-------------------+

3.2. Core Components and Termonilogy

Messaging Nodes: Handle routing and message distribution¶
Topics: Named channels for pub/sub communication¶
Streams: Bidirectional communication channels¶
Services: Application-specific RPC definitions¶

3.2.1. Meassging Nodes

Nodes are essential components of the SLIM architecture. They handle routing and message distribution between agents and manage the communication infrastructure. Meassaging Nodes are composed of two main tables: the connection table and the subscription table.¶

3.2.1.1. Connection Table

The connection table maintains interfaces with neighboring nodes and local applications. It is responsible for:¶

Establishing and managing connections with other Gateway Nodes¶
Maintaining active connections with local applications¶
Handling connection setup, teardown, and error recovery¶

The connection table entries include:¶

Node ID: Unique identifier for the neighboring node or local application¶
Connection Status: Current status of the connection (e.g., active, inactive, error)¶
Connection Parameters: Details such as IP address, port, and security credentials¶

3.2.1.2. Subscription Table

The subscription table is used to map topic subscriptions to neighboring nodes. It manages the distribution of messages based on topic subscriptions and ensures efficient routing of pub/sub messages. The subscription table entries include:¶

Topic: The name of the topic to which the subscription applies¶
Subscriber Node IDs: List of node IDs that have subscribed to the topic¶
Subscription Status: Current status of the subscription (e.g., active, inactive)¶

The subscription table is responsible for:¶

Managing topic subscriptions from local applications and neighboring nodes¶
Routing messages to the appropriate subscribers based on topic subscriptions¶
Handling subscription updates, additions, and removals¶
Ensuring efficient and reliable message delivery¶

By maintaining these tables, Meassaging Nodes facilitate seamless communication and message distribution in a SLIM network, enabling real-time interactive AI applications at scale.¶

4. Security Considerations

SLIM relies on the Messaging Layer Security (MLS) protocol to provide end-to-end security for group communications between agents.¶

4.1. MLS Integration

SLI uses MLS for the following security properties:¶

End-to-end encryption for all agent communications¶
Forward secrecy and post-compromise security¶
Group key management and membership changes¶
Scalable group messaging security¶

4.2. Authentication and Identity

Each agent MUST:¶

Maintain cryptographic identities compatible with MLS¶
Use certified credentials for initial authentication¶
Validate peer credentials during connection establishment¶
Support credential revocation and rotation¶

4.3. Group Security

MLS provides the following guarantees for agent groups:¶

Continuous group key updates¶
Secure member addition and removal¶
Protection against message forgery¶
Perfect forward secrecy for all messages¶

4.4. Operational Security

Implementations MUST:¶

Maintain secure key storage¶
Support MLS epoch advancement¶
Implement proper credential management¶
Monitor for security events¶
Support secure group state recovery¶

4.5. Privacy Considerations

SLIM with MLS provides:¶

Metadata protection¶
Group membership privacy¶
Participant anonymity options¶
Traffic analysis resistance¶

4.6. Implementation Requirements

Implementations MUST NOT:¶

Use non-MLS encryption schemes¶
Support downgrades to less secure modes¶
Allow plaintext communication¶
Skip credential verification¶