COOP (Council of Oracle Protocol) and ZMQ (Zero Message Queue)

 In Cisco ACI (Application Centric Infrastructure), both COOP (Council of Oracle Protocol) and ZMQ (ZeroMQ) play critical roles in the control-plane communication between switches (leaves and spines), but they serve different purposes and operate at different levels. Let’s break down the difference and their relationship:

---

🔹 What is COOP in Cisco ACI?

📌 Purpose:

COOP is the control-plane protocol used by leaf switches to register endpoint information with spine switches in Cisco ACI.

📌 Function:

• It is used by leaf switches to tell the spine(s) about endpoints (MAC, IP, EPG, etc.) they’ve learned.
• Spines act as COOP databases and maintain a distributed mapping table of which leaf has which endpoint.
• This allows for location-based routing (instead of flooding like in traditional Ethernet).

---

🔹 What is ZMQ (Zero Message Queue) in Cisco ACI?

📌 Purpose:

ZMQ (ZeroMQ) is a messaging library used within Cisco ACI to transport messages between system components (e.g., between leaf and spine switches).

📌 Function:

• Acts like a messaging bus.
• Enables high-performance publish/subscribe or request/response messaging.
• It’s used under the hood to deliver control-plane messages—including COOP messages.

---

✅ Does COOP Use ZMQ?

Yes.

COOP uses ZMQ as its transport mechanism to send and receive messages between leaf and spine switches.

---

🔍 How Does COOP Use ZMQ?

Here’s the flow simplified:

1. A leaf switch learns a new endpoint (say, a VM with MAC/IP).
2. The leaf constructs a COOP message with the endpoint details.
3. This COOP message is encapsulated in a ZMQ message.
4. The ZMQ library sends this message to the appropriate spine switch (COOP database).
5. The spine decodes the COOP message and updates its COOP database.

Diagrammatically:

less

CopyEdit

[Leaf Switch]

    |

    |--> [COOP Message Created]

    |

    |--> [Wrapped in ZMQ Message]

    |

    |--> [ZMQ Sends Message to Spine]

    |

[Spine Switch (COOP DB)]

    |

    |--> [ZMQ Receives Message]

    |

    |--> [COOP Message Extracted & DB Updated]

---

🆚 Summary: COOP vs ZMQ

Feature	COOP	ZMQ
Purpose	Control-plane protocol for endpoint learning	Messaging library used for data transport
Scope	Endpoint registration between leaf & spine	Messaging between ACI components
Layer	Application-layer protocol	Transport mechanism (middleware)
Relationship	Payload Protocol	Transport Protocol
Used By	Leaf-to-Spine communication	All ACI components (APICs, Leafs, Spines)

---

✅ Example of Usage:

• You might see coop messages being passed between leaf and spine switches in packet captures.
• If you dig deeper, those messages are often encapsulated using ZMQ frames, showing how COOP rides on top of ZMQ.