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ARP Broadcast Reduction for Large Data Centers

Document Type Expired Internet-Draft (individual)
Expired & archived
Authors Anoop Ghanwani , Himanshu C. Shah , Dr. Nabil N. Bitar
Last updated 2012-05-03 (Latest revision 2011-10-31)
RFC stream (None)
Intended RFC status (None)
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
RFC Editor Note (None)
IESG IESG state Expired
Telechat date (None)
Responsible AD (None)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft is available in these formats:


With advent of server virtualization technologies, a host is able to support multiple Virtual Machines (VMs) in a single physical machine. Data Centers can leverage these capabilities to instantiate on the order of 10s to 100s of VMs in a single server with current technology. It is conceivable that this number can be much higher in the future. Each VM operates as an independent IP host with a set of Virtual Network Interface Cards (vNICs), each having its own MAC address and mapping to a physical Ethernet interface. These physical servers are typically installed in a rack with their Ethernet interfaces connected to a top-of-the-rack (ToR) switch. The ToR switches are interconnected through End-of-the-Row (EoR) or aggregation switches which are in turn connected to core switches. As discussed in [ARP-Problem] the host VMs use ARP broadcasts to find other host VMs and use periodic (broadcast) Gratuitous ARPs to refresh their IP to MAC address binding in other VM hosts. Such broadcasts in a large data center with potentially thousands of VM hosts in a Layer 2 based topology can overwhelm the network. This memo proposes mechanisms to reduce the number of broadcasts that are sent throughout the network. This is done by having the ToRs intelligently process ARP and frames, rather than simply broadcasting them throughout the broadcast domain. While this document addresses ARP, the Neighbor Discovery mechanisms used by the IPv6 hosts that make use of multicast rather than broadcast also pose similar issues in the Data Center. The solutions defined herein should be equally applicable to hosts running IPv6. The details will be specified in a subsequent revision.


Anoop Ghanwani
Himanshu C. Shah
Dr. Nabil N. Bitar

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)