See the OCEAN CITY page.

How can I improve latency problems with a Cerowrt router?

A: The router is configured with QoS (Quality of service) OFF, and the defaults more suitable for US cable than elsewhere. You should go to the Network->Qos screen on the cerowrt router configuration page, turn off QoS, run a suitable bandwidth performance test and then re-enable QoS with more suitable up/download values a few percentage points less than what the bandwidth test shows you. This is “bandwidth” shaping the connection, to attempt to limit the filling of queues in the broadband equipment. Unfortunately, it also means defeating features such as Comcast’s PowerBoost, and it cannot take into account other dynamic changes in availability of bandwidth caused by your neighbors or even the temperature.

We note that SPEEDTEST reports misleading results on broad band service which provides temporary bandwidth boosts such as Comcast’s Poerboost, and we are working on a better test.

Enabling QoS (with sane values) will make it more possible for you and your family to do more work simultaneously - doing uploads while your son is downloading and your daughter is making phone calls and your spouse is playing games, with fewer complaints from everyone.

Disabling QoS will make single stream downloads run nearly as fast as possible at the expense of other activities. Sometimes. See: bloat:Daddy why is my Internet Slow Today?

QoS set to good values is best. Getting good values is hard. We’re working on it.

QoS doesn’t seem to do any good! I can’t do a big upload/download and make a phone call!

Decrease your up and download speeds somewhat until you can do both, in 256kb increments (or by a binary search between 60% and 100% of your provisioned bandwidth).

Does Cerowrt “phone home”?

A: No, it does not. Well, it does, sort of - There is an image on the onboard web pages that is maintained at bufferbloat.net. The cosmic background bufferbloat detector can (but doesn’t always) connect to a ntp server in the bufferbloat pool.

Cerowrt does come with multiple tools, such as snmp, that make collecting statistics about it’s performance easier.

A: The characteristics of wired and wireless, as well as the uberwrt:guest and uberwrt:babel concepts, are sufficiently different to warrant making a clear distinction between them for uberwrt:internal QoS to work well.

See also device naming scheme for more details.

How is routing done in CeroWrt, since the interfaces are routed rather than bridged?

IPv4 is behind NAT by default and broken into 8 static /27 subnets to limit the horrendous impact of multicast/broadcast on wireless. Since a home router is the default gateway, no routing protocol is needed in that case. For other routers in the home, we mesh using babel.

IPv6 is autogenerated from 6to4 or 6in4, fed into radvd, and distributed from there. Help supporting 6rd and DHCPv6-PD is welcome (dibbler is available in RC6 for those who want to experiment).

Core routing protocol is babel for IPv6 and IPv4, radvd is on for older clients, and all of quagga (ospf, bgp etc) is also available.

What about 6rd? (#273)

At one point we had 6rd in CeroWrt, but may not have included the patches in the latest releases. We’ll put it into RC7 if it is MIA. Please let us know in #273 if 6rd is MIA.

Comcast’s 6rd trial was so lame as the only way to use it (as they only delegated a /64) was ahcp + babel, which hands out and routes /128s by default.

6to4 - being /48 - was easily subnettable and thus, usable with older routing mechanisms like radvd - so we went back to that, after a few weeks with 6rd and Comcast. Comcast is not planning to go forward with 6rd but has deployed geographically dispersed production 6to4 relays which have worked well for us. Help testing 6rd on other ISP’s would be a great help.

Why so many SSIDs on the wireless interfaces?

A: 2.4 ghz spectrum tends to be polluted by many other wireless devices. If your client (laptop, whatever) supports 5Ghz operation, you really want to use that SSID (clearly delineated by a “5” postfix) to get higher performance operation.

You can make all the SSIDs be the same if you like in the Cerowrt router configuration pages, but nanog recomends training users “to choose the one on 5”.

Why guest interfaces?

A: Wireless spectrum is intrinsically shared. It makes sense to share it when possible, and also keep your own network safe.

What’s this babel thing?

A: wisp6:Wiki|Wireless mesh networking.

How do I disable the guest/babel interfaces?

A: Firewalling is a complex problem. “Guest” networks are for visitors to your lan, they do not have access to the wired or primary wireless lan (unless unsecured), but do have access to the Internet. You can grant access to guest networks that does not extend to your primary network.

To secure (rather than disable entirely) your guest networks, the simplest method is merely to assign WPA2 keys to the guest networks that guests won’t know.

OR, you can remove the guest networks entirely. Removing the interfaces entirely (which is doable) also requires removing the firewall rules for the guest interfaces in order to work right, as well as a reboot, and recreating them will be difficult.

This is more complex than I’m used to!

A: This is a research project. We hope to make things simpler.

This is cool! What else can this puppy do?

A: See: Cool things to do with a cerowrt router

To edit this page, submit a pull request to the Github repository.
RSS feed

Recent News & Articles

Mar 12, 2017 Wiki page
Make-Wifi-Fast Project
Mar 10, 2017 Wiki page
What Can I Do About Bufferbloat?
Feb 10, 2017 Wiki page
More about Bufferbloat
Dec 27, 2016 Wiki page
RRUL Chart Explanation

Find us elsewhere

Bufferbloat Mailing Lists
#bufferbloat on Twitter
Google+ group
Archived Bufferbloat pages from the Wayback Machine


Comcast Research Innovation Fund
Nlnet Foundation
Shuttleworth Foundation

Bufferbloat Related Projects

Congestion Control Blog
Lede Project (OpenWrt)
Flent Network Test Suite
The Cake shaper

Network Performance Related Resources

Jim Gettys' Blog - The chairman of the Fjord
Toke's Blog - Karlstad University's work on bloat
Voip Users Conference - Weekly Videoconference mostly about voip
Candelatech - A wifi testing company that "gets it".