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Description of Address Resolution Protocol (ARP) caching behavior in Windows Vista TCP/IP implementations
Article ID: 949589 - View products that this article applies to.
This article describes the Address Resolution Protocol (ARP) caching behavior in Windows Vista TCP/IP implementations.
ARP caching behavior has been changed in Windows Vista. The TCP/IP stack implementations in Windows Vista comply with RFC4861 (Neighbor Discovery protocol for IP version 6 [Ipv6]) for both the IPv4 and the IPv6 Neighbor Discovery process.
The ArpCacheLife and ArpCacheMinReferencedLife registry entries determine how the ARP cache is maintained in Windows XP and in Windows Server 2003. These registry entries no longer apply to Windows Vista.
In the new Windows Vista TCP/IP stack implementation, hosts create the neighbor cache entries when there is no matching entry in the neighbor cache. ARP cache entry for IPv4 is an example of a neighbor cache entry. After the entry is successfully created in the neighbor cache, the entry may change to the "Reachable" state if the entry meets certain conditions. If the entry is in the "Reachable" state, Windows Vista TCP/IP hosts do not send ARP requests to the network. Therefore, Windows Vista TCP/IP hosts use the information in the cache. If an entry is not used, and it stays in the "Reachable" state for longer than its "Reachable Time" value, the entry changes to the "Stale" state. If an entry is in the "Stale" state, the Windows Vista TCP/IP host must send an ARP request to reach that destination.
The "Reachable Time" value is calculated as follows:
Reachable Time = BaseReachable Time × (A random value between MIN_RANDOM_FACTOR and MAX_RANDOM_FACTOR)RFC provides the following calculated results.
Therefore, the "Reachable Time" value is somewhere between 15 seconds (30 × 0.5 seconds) and 45 seconds (30 × 1.5 seconds). If an entry is not used for a time between 15 to 45 seconds, it changes to the "Stale" state. Then, the host must send an ARP Request for IPV4 to the network when any IP datagram is sent to that destination.
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To see the current "Reachable Time" value, follow these steps:
http://www.ietf.org/rfc/rfc2461.txtFor more information about TCP/IP registry values for Windows Vista and for Windows Server 2008, visit the following Web site:
http://download.microsoft.com/download/c/2/6/c26893a6-46c7-4b5c-b287-830216597340/TCPIP_Reg.docThe third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.
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Article ID: 949589 - Last Review: January 21, 2010 - Revision: 4.0