ppp0 and it's txqueuelen with HSDPA gsm modems
Hello
What would be "optimal" value for ppp0 device's txqueuelen, when it is used with HSDPA gsm modem for link which downlink speed is 1Mbit/s and uplink speed is 384kbit/s and ping ~80..100 ms? Is the default value 3 just OK?
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Best Regards, Jar
Quoted 9 lines
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Jar
Sent: 21. oktober 2008 20:44
To: [email protected]
Subject: ppp0 and it's txqueuelen with HSDPA gsm modemsHello
Quoted 7 lines
What would be "optimal" value for ppp0 device's txqueuelen, when it is used with HSDPA gsm modem for link which downlink speed is 1Mbit/s and uplink speed is 384kbit/s and ping ~80..100 ms? Is the default value 3 just OK?
--
Best Regards, Jar
Jar,
I would suggest using normal TCP calculation, i.e. that you dimension the txqueue size after the "BDP rule": bandwidth x delay product. Using your outbound numbers this is:
1,000,000 x 0.1 = 100,000 bits = 12,500 bytes. Assuming 1500 byte packets, this is txqueue = 12,500 / 1500 = 8.3 packets. So you could try txqueue size in the region 8-10, this should prevent queue starvation at packet drop events caused by traffic overload, even if you only have one single TCP flow.
Best regards,
Arne Lie
SINTEF ICT, Dept. of Communication Systems
e-mail: [email protected]
Quoted 8 lines · Lie Arne
Quoted 7 lines
What would be "optimal" value for ppp0 device's txqueuelen, when it is used with HSDPA gsm modem for link which downlink speed is 1Mbit/s and uplink speed is 384kbit/s and ping ~80..100 ms? Is the default value 3 just OK?
--
Best Regards, Jar
Quoted 8 lines
I would suggest using normal TCP calculation, i.e. that you dimension the txqueue size after the "BDP rule": bandwidth x delay product. Using your outbound numbers this is:
1,000,000 x 0.1 = 100,000 bits = 12,500 bytes. Assuming 1500 byte packets, this is txqueue = 12,500 / 1500 = 8.3 packets. So you could try txqueue size in the region 8-10, this should prevent queue starvation at packet drop events caused by traffic overload, even if you only have one single TCP flow.
OK, thanks. But is txqueuelen for transmit data only and then the downlink value (384kbit/s) should be used in the calculation? With 384kbit/s the txqueuelen would be 3.2 which is quite same as ppp0 default 3.
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Best Regards, Jar