Configuring the PathBuilder S200 Series Switch for Bridging Operation

Increasing the frame size also causes the reduction in frame overhead. If a 1000 byte data packet required a 50 byte header (frame + IP + TCP), then if 2000 bytes were placed in the frame with the same frame, the difference in overhead is 50/1000 = 5% versus 2.5%. As the size of the data increases, the overhead becomes even less. However, at these levels, the gain is marginal. Other factors may reduce this method of gain considerably. For example, intermediate systems have a limit on how large a frame they can handle.

As the size of the frame becomes larger, there is a corresponding increase in the time the frame spends in transmission media. The error rate of transmission media is finite and becomes a problem when the time for transmitting a frame becomes long enough that the probability of an error occurring during the transmission time is likely. An error on a large frame with its subsequent retransmission means the media are used with unproductive transmissions and reduced efficiency.

Standard Frame

In general, these industry standards can be used as a guideline for selecting the

Sizes

maximum frame size.

 

 

 

 

 

Max Frame Size

Line Speed Range (kbps)

 

 

 

 

512

9.6 to 38.4

 

 

 

 

1500

38.4 to 56

 

 

 

 

2052

56 to 1544

 

 

 

 

4472

1544

 

 

 

Bridge Transit Time The transit time for bridged traffic within a PathBuilder S200 series switch is fixed to an upper bound of approximately one second. If the time is exceeded, the frame is discarded. This avoids extra traffic being sent (especially due to LLC2 recovery procedures).

Duplicate frames will frustrate normal recovery procedures and cause extra traffic to be generated. When a frame is discarded in this manner, the port statistic in the Detailed Port Stat screen displays “Frames Discarded: Congestion.”

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Bridging

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EXP Computer S200 manual Standard Frame, Sizes, Maximum frame size, Max Frame Size Line Speed Range kbps