Packet loss between two P devices

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Mar 26th, 2007
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Hi all,

Doing some tests (extended ping) we can see packets loss between two P devices.

There is about 1% packet loss sending more than 500 packets of size 12000. With 500 or so works good.

The link is a direct fiber link.

Any idea?

Thanks in advance,

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tomredmond Mon, 03/26/2007 - 03:53
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What is your MTU size? normally it set about 1500 therefore a packet of size 500 will pass unfragmented, however one of 12000 will be fragmented. I have seen in the past where there is fragmentation and one of the devices is busy then the odd packet can be lost.

enriquebs Mon, 03/26/2007 - 03:59
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The MTU size is 1508. I don't know whether it's normal or the size shouldn't have influence... the link is direct, I suppose that shouldn't be a packet loss even using a 12000 bytes ping

dave.keith Mon, 03/26/2007 - 10:00
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I've never been a big fan of using ICMP Echo Request/Rely for measuring packet loss. It seems to me that the replying host may sometimes not bother to reply, which gets interpretted as packet loss. If you have some understanding of the typical (benchmark) performance of a TCP session across that link, then an increase in TCP retransmits may be an indicator of increased packet loss. If retransmissions are normal then my guess would be that the 1% ping loss can be attributed to other sources than the link.



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