MTU on 3G interface

[Guest mrmrmrmr]

Hi,

What is the default MTU on 3G interface for Dell Streak ? more specifically, Steve's Froyo 1.3.0 ?

And how can we change it ?

[Guest vinokirk]

Why would you want to change it? Isn't the MTU set by the cellular network?

[Guest mrmrmrmr]

I wantto use a sip client which supports Video+Audio

When video is enabled, SIP invite packet is arounf 1480 bytes which is bigger than the current MTU.

I don't know the current MTU but I know it is lower than 1480.

[Guest Stephen Hyde]

probably 1472 but im not sure if its even changeable in android

[Guest fards]

adb shell 

$ su

# sysctl -a|grep mtu

will give you what you need.. on mine I get

sysctl: error reading key 'net.ipv4.route.flush': Permission denied

net.ipv4.route.mtu_expires = 600

net.ipv4.route.min_pmtu = 552

net.ipv4.ip_no_pmtu_disc = 0

net.ipv4.tcp_mtu_probing = 0

net.ipv6.conf.all.mtu = 1280

net.ipv6.conf.default.mtu = 1280

net.ipv6.conf.lo.mtu = 16436

net.ipv6.conf.dummy0.mtu = 1500

net.ipv6.conf.rmnet0.mtu = 1500

net.ipv6.conf.rmnet1.mtu = 1500

net.ipv6.conf.rmnet2.mtu = 1500

net.ipv6.conf.sit0.mtu = 1480

net.ipv6.conf.usb0.mtu = 1500

net.ipv6.conf.eth0.mtu = 1500

sysctl: error reading key 'net.ipv6.route.flush': Permission denied

net.ipv6.route.mtu_expires = 600

haven't tried changing mtuprobe to 1 yet..

to make changes (net. are immediate I think)

do sysctl -w whatever=whatvalue

that will survive till reboot

[Guest mrmrmrmr]

thank you. I'll try that when I get home.

[Guest mrmrmrmr]

I couldn't figure out which parameter to change for affecting ipv4 mtu on interface rmnet0

which one ?

[Guest mrmrmrmr]

any ideas ?

[Guest fards]

is it using ipv4 ?

tried changing those to 1 and see what happens?

net.ipv4.ip_no_pmtu_disc = 0

net.ipv4.tcp_mtu_probing = 0

[Guest mrmrmrmr]

doesn't work...

still my sip packets get fragmented.

anyway, I also tried :

ifconfig rmnet0 mtu 1500

and

ip link set rmnet0 mtu 1500

command is accepted but result didn't change.

maybe it's because of the network.