Multiple Registration Protocol

Multiple Registration Protocol (MRP), which replaced Generic Attribute Registration Protocol (GARP), is a generic registration framework defined by the IEEE 802.1ak amendment to the IEEE 802.1Q standard. MRP allows bridges, switches or other similar devices to register and de-register attribute values, such as VLAN identifiers and multicast group membership across a large local area network. MRP operates at the data link layer.

History

GARP was defined by the IEEE 802.1 working group to provide a generic framework allowing bridges (or other devices like switches) to register and de-register attribute values such as VLAN identifiers and multicast group membership. GARP defines the architecture, rules of operation, state machines and variables for the registration and de-registration of attribute values. GARP was used by two applications: GARP VLAN Registration Protocol (GVRP) for registering VLAN trunking between multilayer switches, and by the GARP Multicast Registration Protocol (GMRP). The latter two were both mostly enhancements for VLAN-aware switches per definition in IEEE 802.1Q.

Multiple Registration Protocol (MRP) was introduced in order to replace GARP, with the IEEE 802.1ak amendment in 2007. The two GARP applications were also modified in order to use MRP. GMRP was replaced by Multiple MAC Registration Protocol (MMRP) and GVRP was replaced by Multiple VLAN Registration Protocol (MVRP). This change essentially moved the definitions of GARP, GVRP, and GMRP into an 802.1Q-based environment, implying they were already VLAN aware. This also allowed for significant streamlining of the underlying protocol without much change to the interface of the applications themselves.

The new protocol and applications fixed a problem with the old GARP-based GVRP-based system, where a simple registration or a failover could take an extremely long time to converge on a large network, incurring a significant bandwidth degradation.

It is expected GARP will be removed from IEEE 802.1D at some point in the future.

Multiple MAC Registration Protocol

Multiple MAC Registration Protocol is a data link layer (layer 2) protocol to register group MAC addresses (i.e. multicast) on multiple switches. It is an MRP application, originally defined in IEEE 802.1ak-2007 and subsequently included in 802.1Q. It replaced the 802.1D-based GMRP. The purpose of MMRP is to allow multicast traffic in bridged LANs to be confined to areas of the network where it is required.

Multiple VLAN Registration Protocol

MVRP, which replaced GVRP, is a standards-based Layer 2 network protocol, for automatic configuration of VLAN information on switches. It was defined in the 802.1ak amendment to 802.1Q-2005.

Within a layer 2 network, MVRP provides a method to dynamically share VLAN information and configure the needed VLANs. For example, in order to add a switch port to a VLAN, only the end port, or the VLAN-supporting network device connected to the switch port need be reconfigured, and all necessary VLAN trunks are dynamically created on the other MVRP-enabled switches. Without using MVRP, either a manual configuration of VLAN trunks or use of a manufacturer's proprietary method is necessary.

It is through MVRP that dynamic VLAN entries will be updated in the filtering database. In short, MVRP helps to maintain VLAN configuration dynamically based on current network configurations.

802.1Q allows for:

1. Dynamic configuration and distribution of VLAN membership information by means of the MVRP
2. Static configuration of VLAN membership information via management mechanisms, which allow configuration of static VLAN registration entries.
3. Combined static and dynamic configuration, in which some VLANs are configured via management mechanisms and for other VLANs, MVRP is relied on to establish the configuration.

MVRP defines a MRP application that provides the VLAN registration service. MVRP makes use of MRP Attribute Declaration (MAD) and MRP Attribute Propagation (MAP), which provide the common state machine descriptions and the common information propagation mechanisms defined for use in MRP-based applications. MVRP provides a mechanism for dynamic maintenance of the contents of dynamic VLAN registration entries for each VLAN, and for propagating the information they contain to other bridges. This information allows MVRP-aware devices to establish and update dynamically their knowledge of the set of VLANs that currently have active members, and through which ports those members can be reached. The main purpose of MVRP is to allow switches to automatically discover some of the VLAN information that would otherwise need to be manually configured.

Legacy GVRP details

The replaced GVRP was essentially the same thing, but it used the services of the 802.1D-based GARP application. GVRP made use of GARP Information Declaration (GID) and GARP Information Propagation (GIP), which correspond to the MAP and MAD in MRP. It was defined in the original release of 802.1D-1998 until it was replaced by MVRP.

It was replaced because the non-VLAN-aware GARP had serious deficiencies when operating in large VLAN networks.

Multiple Stream Registration Protocol

Multiple Stream Registration Protocol (MSRP) is an application of the Multiple Registration Protocol (MRP), defined in the IEEE 802.1Qat amendment to the IEEE 802.1Q standard. It functions within the Stream Reservation Protocol (SRP) framework developed by the Audio Video Bridging (AVB) task group and standardized in IEEE 802.1Q-2011. MSRP enables endpoints—known as Talkers and Listeners—to register, advertise, and reserve network resources (bandwidth, priority, VLAN) to ensure end-to-end Quality of Service (QoS) across bridged LANs.

MSRP uses three main message types:

• Talker Advertise – announces an available stream with specific parameters including StreamID, VLAN ID, priority, traffic specification, and accumulated latency.
• Listener Ready – signals that a Listener is prepared to receive the stream, which triggers resource reservation along the path.
• Talker Failed / Listener Failed – indicate reservation failure when resources are insufficient at any hop.

Protocol operation

1. A Talker sends a Talker Advertise message to initiate reservation.
2. Each intermediate bridge evaluates available bandwidth, applies credit-based shaping, and updates the accumulated latency field.
3. If resources are sufficient, the message is forwarded; otherwise, a Talker Failed is generated including failure location and reason.
4. Upon reaching a Listener, a Listener Ready response propagates back, locking in resources per hop.
5. Reservation teardown occurs upon withdrawal of advertisements or readiness messages.

Key features

• Distributed admission control – per-hop decision-making prevents oversubscription of network resources.
• TSN/AVB integration – interoperates with MVRP, MMRP, gPTP, and credit-based shaping to form synchronized, QoS-guaranteed domains.
• Latency awareness – accumulates worst-case per-hop latency; supports SR‑Class A (≤ 2 ms) and Class B (≤ 50 ms) streams over up to seven hops on 100 Mb/s networks.

Wireless/BSS environments

In 802.11 BSS scenarios, an Access Point may act as a Designated MSRP Node, aggregating MSRP messages and integrating with 802.11 QoS mechanisms to support Talker/Listener signaling.

Limitations

MSRP operates under several constraints:

• Supports only one active Talker per StreamID at a time.
• Lacks built-in redundancy or aggregation support.
• Only fixed-bitrate, unidirectional streaming is supported; not suitable for bidirectional/variable-rate flows like VoIP.

Evolution

While MSRP remains a core part of the decentralized SRP model, IEEE 802.1Qcc (2018) introduced centralized management (CNC/CUC) and optimized timers. MSRP continues to operate on UNI links in hybrid deployments.

See also

• VLAN Trunking Protocol (VTP): a similar but proprietary protocol from Cisco

References

• IEEE 802.1D standard (PDF)
• IEEE 802.1Q Standard (PDF)
• IEEE 802.1ak standard (PDF) and its corrigendum