RFC4638 support?

Forums › 2degrees (including Slingshot, Orcon, Flip, Stuff Fibre, MyRepublic, 2talk and Vocus) › RFC4638 support?

kamicrazy

17 posts

Geek

#179392 7-Sep-2015 02:29

Hi,

Moving house into an UFB ready, looking for a new ISP.

Snap/2Degrees ticks almost all my wishlist (huge upload, ipv6, static IP's)

Do they support RFC 4638 like Spark does? Is it possible to have ppp mtu 1500?

If they don't I'll have to settle for myrepublic, which I'd rather not.

SaltyNZ

8234 posts

Uber Geek

Trusted

2degrees

Lifetime subscriber

#1380905 7-Sep-2015 08:49

Although I cannot speak to the support or otherwise of RFC 4638, I think that realistically, lack of RFC 4638 support isn't going to make or break the speed of your connection. The fact that NZ is on the end of a long thin wire is greatly more important. Besides, unless your entire home network is gigabit ethernet with jumbo frames enabled (which can already be saturated by 1500-byte frames), your MTU size is only going to increase by a whole 8 bytes. If it worries you that much, setting everything else to 1492 will achieve the same effect.

iPad Pro 11" + iPhone 15 Pro Max + 2degrees 4tw!

These comments are my own and do not represent the opinions of 2degrees.

kamicrazy

17 posts

Geek

#1381008 7-Sep-2015 11:25

I'm not the typical home user and my preference for a 1500 MTU is not related to speed or gaming concerns.

I prefer 1500 MTU for compatibility reasons. I can appreciate your comment though that its not useful for the majority of people.

fe31nz

1232 posts

Uber Geek

#1381439 7-Sep-2015 22:18

No, I do not think they support 1500 byte frames over PPP. I tried a couple of months back, and it did not work. However, since then they have changed the router making my PPP connection to a different device (its MAC address changed and its IPv6 connection over PPP started working for static prefixes without needing to do DHCPv6). I have not tested it again since.

It is a real pain not to have 1500 byte frames as it makes for problems with MTU path discovery and breaks IPv6 - I have to have an IPv6 MTU of 1492 advertised internally by my router in order to get external IPv6 connections to work.

kamicrazy

17 posts

Geek

#1381572 8-Sep-2015 09:45

Hi fe31nz

Thanks for providing your info. I assume you tested this with an Edgerouter, which is my choice of router too.

I have similar reasons for wanting 1500 MTU, it avoids problems like broken path discovery and a lot of stuff assumes a 1500 MTU

If you ever get to test it again, would you please share the results, this sort of info was impossible to find.

Sounddude

I fix stuff!
1928 posts

Uber Geek

Trusted

2degrees

Lifetime subscriber

#1381601 8-Sep-2015 10:20

For what its worth, Orcon uses DHCP rather than PPP, therefor supports 1500byte MTU's.

fe31nz

1232 posts

Uber Geek

#1382083 8-Sep-2015 21:55

kamicrazy: Hi fe31nz

Thanks for providing your info. I assume you tested this with an Edgerouter, which is my choice of router too.

I have similar reasons for wanting 1500 MTU, it avoids problems like broken path discovery and a lot of stuff assumes a 1500 MTU

If you ever get to test it again, would you please share the results, this sort of info was impossible to find.

Yes, I am running a Ubiquiti EdgeRouter Lite (firmware 1.7.0).

I decided to test again today, and it appears that an MTU of 1500 is now supported! I made these changes to my config:

set system offload ipsec disable
set system offload ipv4 forwarding disable
set system offload ipv4 pppoe disable
set system offload ipv4 vlan disable
set system offload ipv6 forwarding disable
set system offload ipv6 vlan disable
set interfaces ethernet eth0 mtu 1508
set interfaces ethernet eth0 vif 10 mtu 1508
set interfaces ethernet eth0 vif 10 pppoe 0 mtu 1500
delete firewall options mss-clamp
delete interfaces ethernet eth1 ipv6 router-advert link-mtu 1492
delete interfaces ethernet eth2 ipv6 router-advert link-mtu 1492

The disabling of offloading was so that I could make sure that tshark could capture all the packets on the PPP connection, and the rest are for changing to MTU of 1500 and removing the workaround that allowed IPv6 to work with the smaller MTU over PPP.

After committing the changes, I unplugged the ERLite from the ONT and ran tshark on it to capture all the traffic on the eth0.10 interface. Then I plugged it into the ONT again and waited for the PPP connection to come up. Once it was up, the eth0.10 interface had an MTU of 1508 and pppoe0 had 1500.

Then I booted my test Windows 10 PC, and where the "netsh interface ipv6 show subinterfaces" command used to show an MTU of 1492, it now showed 1500. So I tried the command "ping -6 -n 2 -l 1452 google.com" and it worked. Previously, the maximum ping packet size that worked was 1444. Then I tried using Firefox to go to http://www.facebook.com, which used to fail without the "ipv6 router-advert link-mtu 1492" options due to large packets going missing. But now it worked.

It seems that a while back when Snap had some scheduled maintenance outages, what they were doing was replacing the routers that do the VLAN 10 PPPoE connections for them. Or at least they replaced the one that I connect to from Palmerston North. I noticed at the time that its MAC address had changed. It seems from the MAC address it is now a Juniper box, and it handles an MTU of 1500 for PPP connections.

I am not sure if the 1.7.0 firmware is correctly negotiating RFC4638 though - I could not see any PPP-Max-Payload options being negotiated. Instead, it seems to be negotiating for no MTU or MRU options at all, and accepting a default of 1500 that results. But since it works, that is fine by me.

So now I am going to renable offloading and enjoy the larger packet size. My main Windows 7 box will not actually use the new packet size until I reboot it - it is still remembering the old MTU option in the router advertisment packets it was previously receiving and Windows does not forget that option on receiving a new router advertisment without it. But I had planned a reboot for later tonight anyway.

kamicrazy

17 posts

Geek

#1382113 8-Sep-2015 23:20

Thanks for doing the test, that's great news.

I guess it's a bit of a lottery if it will work for me if I join.

Only way to find out is to try!

Quic Broadband

Move to New Zealand's best fibre broadband service (affiliate link). Free setup code: R587125ERQ6VE. Note that to use Quic Broadband you must be comfortable with configuring your own router.

michaelmurfy

meow
13263 posts

Uber Geek

Moderator

ID Verified

Trusted

Lifetime subscriber

#1382114 8-Sep-2015 23:21

Am on 2degrees broadband (200/200 UFB) and have successfully enabled RFC 4638 on my connection so yes it does work.

As for the huge upload? Well, this speedtest was done on a Chromebook after the MTU change over WiFi and am pretty impressed with how well my WiFi works:

Michael Murphy | https://murfy.nz
Referral Links: Quic Broadband (use R122101E7CV7Q for free setup)

Are you happy with what you get from Geekzone? Please consider supporting us by subscribing.
Opinions are my own and not the views of my employer.