Jumbo Frames; Implementing Jumbo Frames; Jumbo Frames - Simple Network Example - 3Com SuperStack 3 3812 Implementation Manual

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HAPTER PTIMIZING

Jumbo Frames

Implementing Jumbo
Frames
Jumbo Frames —
Simple Network
Example
B
ANDWIDTH
3 Connect port 5 on the core Switch to port 47.
4 Connect port 7 on the core Switch to port 48.
On a standard Ethernet network, the maximum size of a frame is
1518 bytes (1522 bytes if the frame is VLAN tagged); 1500 bytes for data
and 18 bytes as header information (22 bytes if the packet is tagged).
Ethernet frames over the maximum size will be discarded.
Jumbo frames are larger than standard frames with a maximum data size
of 9000 bytes. The size of the header does not change, making jumbo
frames more efficient that conventional Ethernet frames. This is
particularly evident in high-traffic situations.
CAUTION: Devices supporting jumbo frames should be segregated from
other network devices, as network devices that do not support jumbo
frames will see them as malformed frames and will drop the traffic.
Jumbo frames are usually implemented on a network so that endstations
that support jumbo frames can communicate with other similar devices.
Typically the endstations will be servers requiring high bandwidth; for
example as part of a server-farm or participating as part of a distributed
computer.
To ensure that the jumbo frames are sent only to those devices that are
capable of receiving them:
All network devices between the endstations must be compatible with
■
jumbo frames.
The software generating the traffic must be configured so that it only
■
sends jumbo frames to devices capable of accepting them.
Figure 4 shows a simple network with four servers connected to a switch
supporting jumbo frames. Clients are connected to a switch supporting
conventional Ethernet frames.
This configuration would provide fast communication between the
servers while keeping compatibility with existing standards for
communication between the clients and the servers.