Subject: I-D ACTION:draft-shah-armd-arp-reduction-01.txt

From: [email-masked]
Date: Mon, 25 Oct 2010 13:45:01 -0700 (PDT)

A New Internet-Draft is available from the on-line Internet-Drafts 
directories.

	Title		: ARP Broadcast Reduction for Large Data Centers
	Author(s)	: H. Shah
	Filename	: draft-shah-armd-arp-reduction-01.txt
	Pages		: 11
	Date		: 2010-10-25
	
With the emergence 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 server. 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-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 ToR 
   switches intelligently process ARP packets, rather than simply 
   broadcasting them throughout the broadcast domain.  
    
   While this document specifically addresses ARP, the Neighbor 
   Discovery mechanisms used by IPv6 hosts that make use of multicast 
   rather than broadcast also pose similar issues for the data center. 
   The solutions defined herein should be equally applicable to hosts 
   running IPv6.  The details will be specified in a subsequent 
   revision.

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