[j-nsp] RFC2544 on Juniper MX960 10G ports

[Joerg Staedele]

Hi,

so this means that this Linecard is not able to do line-rate forwarding with small frame sizes? What about other cards (20xSFP+2x10G) .. I guess they use exactly the same PFE hardware? So they have this limitation aswell?

I am really confused now because in every document you read that the DPCE's are able to do line-rate at any frame-size?

Regards,
 Joerg

-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Jonathan Lassoff
Sent: Sunday, March 14, 2010 6:55 PM
To: Serge Vautour
Cc: juniper-nsp
Subject: Re: [j-nsp] RFC2544 on Juniper MX960 10G ports

Excerpts from Serge Vautour's message of Thu Feb 18 16:28:44 -0800 2010:
> Hello,
> 
> We recently used a traffic generator to run RFC2544 tests against a Juniper MX960. The 1G ports work flawlessly. 0% packet loss at all frame sizes. 
> 
> The 10G ports  (4x10G "R" card) didn't do as well. They dropped up to 25% packets with certain small frames (ex: 70 byte frames). The packet loss goes away almost completely for frames larger than 100 bytes. Our SE tells us this is normal and is due to how the MX chops the frames up into 64 byte cells inside the PFE. The 4x10G cards have 4 separate PFEs (1 per 10G port) and each of them has 10G of bandwidth. 10G of small frames essentially creates more than 10G of traffic inside the PFE. That explanation may not be 100% correct but I think it paints the right picture.
> 
> Now the questions. Is this a problem on production networks with real world traffic? What about on VPN networks with alot of small frames like VoIP? Has anyone seen this problem creep it's head in production?

Isn't the minimum Ethernet frame size 64 bytes? I think Ethernet II /
Ethernet 802.3 requires this.

Wouldn't this make the problem moot if you're just running Ethernet?

Might be a problem with small ATM cells?

Cheers,
jof
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