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VIRTMSS -- Virtual MSS (Maximum Segment Size) Disclosure Number: IPCOM000202084D
Publication Date: 2010-Dec-03
Document File: 2 page(s) / 21K

Publishing Venue

The Prior Art Database


VIRTMSS -- Disable hardware/adapter largesend feature via user defined setting called Virtual Maximum Segment Size or VIRTMSS

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VIRTMSS -- Virtual MSS (Maximum Segment Size)


Network adapters that offer largesend, that is, an application that send data or a segment greater than TCP Maximum Segment Size (MSS), the segment will be sent to the adapter which fragments into MSS segments. MSS is Maximum Transmit Unit [MTU] less TCP and IP headers -- it is considered packet data or payload for the immediate network.

The purpose of largesend is to offload cpu cycles from the operating system cpu(s) to the adapter's cpu or processing unit to fragment the large segment.

A component view that illustrates where large segment fragmentation occurs:

Largesend enabled:

Application (sends large segment) TCP layer IP layer (does not fragment) adapter interface layer adapter driver hardware/adapter (fragments large segment)

Largesend disabled:

Application (sends large segment) TCP layer IP layer (fragments large segment and pass-along each fragment) adapter interface layer adapter driver hardware/adapter.

Problem to be solved

Largesend may not be optimal or degrade performance for TCP connections; and it does not allow a software mechanism to disable it per network connection or application use.

* If the application sends a large segment and largesend is enabled, then the time between fragments placed on the physical medium such as fiber or copper wire will be minimal or close to each other [as opposed to fragmentation within the IP layer and the in-between layers and time to be placed on "the wire" by the adapter]