FTTC Modem

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Revision as of 11:45, 27 January 2012 by Alexhulse (talk | contribs) (Added info about RFC 4638 and enabling on Linux / OpenWRT)
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With FTTC, BT will supply and install a VDSL modem (the Active NTE in BT speak), You will then need a PPPoE device (router or software) to use the service.

  • PPPoE Service Name = Blank
  • PPPoE username = as supplied, eg x@a.1
  • PPPoE password = as supplied
  • MTU = 1500 (if your equipment can handle baby jumbo frames and RFC 4638), otherwise 1492
  • Auth Protocol CHAP

FTTC Modem

Here is an image of a BT supplied FTTC modem

FTTC Modem.png

The modem is supplied by BT, if it develops a fault then AAISP can contact BT and report a fault.

If the sync light flashes, then there is no sync, and will probably need to be reported as a fault.

Router Throughput

With the switch to FTTC (especially from low sync'd ADSL connections) your modem is suddenly confronted with throughput possibly 10 or even 20 times more than before!

Router Sync Speed Throughput Notes
Linksys WRTU54G-TM 24Mb ~18Mb/sec Running OpenWRT trunk from here. Disconnected PPP due to link saturation at default settings - adjust PPP options for stability
Netgear WNR854T 24Mb 24Mb Running OpenWRT 10.03 (Backfire). Probably capable of more - have asked BT to move cabinet closer, but they seem unwilling!
FireBrick 2700 16Mb 16Mb It should be able to handle around 350Mb/s!

Notes:

  • Green throughput - not bottleneck on connection
  • Red throughput - bottleneck on connection

Billion 7800 Notes

The Billion 7800 is a popular router with our customers, but take note that when configuring the WAN side, it may need a reboot when changing the WAN type (ADSL/eWAN), and then a reboot when changing the WAN Profile.

FireBrick 2700

The Firebrick 2700 is a great router for FTTC, and even bonding FTTC. See the FireBrick pages for more info

Testing and using FTTC with just a computer

You can connect a computer to the FTTC modem directly, and use PPPoE to make a connection to get online. This is good for testing the FTTC modem with a device other than your normal router.

Windows

  1. Control panel, Network and Internet
  2. Click Network Sharing Centre
  3. Click Setup a connection or network
  4. Follow the wizard
  5. You should be online, you may want to check firewall settings

Remember to keep the service name blank


OSX (Apple)

  1. Go to System Preferences, Network
  2. Click the + icon on the bottom/right (you may need to click the unlock icon first)
  3. Interface=PPPoE, Ethernet=Ethernet, Service Name=AAISP
  4. Then will in the account name and password, click Connect (keep service name blank)
  5. You should be online, you may want to check firewall settings

RFC 4638 Information

Some pointers regarding RFC 4638, PPPoE and Linux-based routers.

  1. The wan interface needs to be set to an MTU of 1508 on the assumption that there needs to be room for the 1500 mtu PPP package on the way to the modem (1500 may work - untested though).
  2. You will require the unreleased ppp 2.4.6. In testing, ppp 2.4.5 with the rp-pppoe plugin updated to the latest version seems to work, although a recompile will be necessary. This can be fetched from ppp's website / git.
  3. Using ppp's debug option will allow you to see the rp-pppoe plugin negotiating a PPP-Max-Payload option with the BRAS via an LCP option. If this isn't seen, then your MTU is forced back to 1492.

RFC 4638 on OpenWRT 10.03.1 (Backfire)

Getting RFC4638 on Backfire is somewhat tricky, but do-able if you're feeling like fiddling with code! In order to make it work:

  1. create an OpenWRT build environment for the 10.03.1 release so you compile the new pppd release
  2. adapt the pppd 2.4.4 package definition to pull the 2.4.5 package from ftp.samba.org instead - you will need to update the version to 2.4.5 and the md5sum of the downloaded package.
  3. Pull the ppp 2.4.5 package patches from the (currently) "trunk" release and replace the 2.4.4 patches with these. The 2.4.4 patches are too outdated to apply to ppp 2.4.5.
  4. Use OpenWRT's patch making ability to create a patch that applies to 2.4.5 to update rp-pppoe to the latest release. The process is to create a new patch point in the build_root using quilt (see OpenWRT's wiki - surprisingly easy and well documented!), overwrite the 2.4.5 rp-pppoe plugin with the git version (ugly but it works...) and the generate a new patch to reflect the differences.
  5. Re-compile the ppp package to create an installable .pkg. This is why you created a patch - the OpenWRT compile routine will wipe out any changes you make to the build_root.
  6. Use SCP to copy the new ppp and ppp-mod-pppoe packges to your router's /tmp
  7. Install the updated packages with opkg on your router.
  8. Adjust yout /etc/config/network so that the MTU is now 1508
  9. Add the debug option to /etc/ppp/options
  10. Issue an ifup wan
  11. Have a look at the output of logread and watch what happens
  12. Check your interfaces with ifconfig
  13. Check clueless to see if it sees your mru 1500