Linux and Multiple Internet Uplinks: a New Tool 80
New submitter Alessandro Zarrilli writes: Linux has been able do multipath routing for a long time: it means being able to have routes with multiple gateways and to use them in a (weighted) round-robin fashion. But Linux is missing a tool to actively monitor the state of internet uplinks and change the routing accordingly. Without it, from a LAN perspective, it's like having a RAID-0: just one uplink goes down and all of your LAN-to-WAN traffic goes down too. Documentation and examples on the subject are lacking; existing solutions are few and deeply integrated in firewall/routing specific distributions. To address these issues, a new standalone tool was just released: Fault Tolerant Router. It also includes a complete (iptables + ip policy routing) configuration generator.
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As much as it's medium rare steak compatible. They're compatible in the fact that they're completely independent (and unrelated) of one another.
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Actually, the analogy is quite apt.
As TFS talked about configuring it (load sharing with no monitoring), they would be getting twice the bandwidth, with the same drawbacks as RAID0: If either connection goes down, you have a (mostly) unusable system (because with no monitoring , half your packets are still going out the broken link).
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>RAID 0 has zero redundancy.
That's what he said.
"just one uplink goes down and all of your LAN-to-WAN traffic goes down too."
Strange (Score:5, Interesting)
Strange.
I was using routing patches to Linux nearly 7 years ago to do this (admittedly it wasn't in the stock kernel, but the patches weren't huge)... you were able to specify multipath and multiple gateways and if one route went down, the others were prioritised and would take over, and also your upstream etc. were balanced properly and took account of failing routes automatically without any kind of daemon etc. running.
I ran a school off multiple ADSL and even 3G connections with it - the only manual maintenance I ever had to do was to put the ADSL modems onto a SMS-controlled relay (SMS came in on the same 3G stick!) because our ISP would often give us "dead" sessions if they'd had problems (where you'd get PPP and an IP and a remote gateway but couldn't do anything across them) and we were then able to manually reset if necessary. My bursar and I used the system for five years like that, only ever resetting it to enable VPN when all the upstream routes had got dead sessions, and that less than once or twice a year.
And, no, we didn't have to do much. It was a stock Slackware install with one set of patches to a (2.6?) kernel to enable the multipath routing etc. Pretty well advertised at the time, one plain page of simple patches (I remember porting them myself to a newer kernel version, just before the new diffs came out), I'll try and dig it up.
And "RAID-0 for upstream"? Bollocks. It "just worked" whatever interfaces were up (proven by it would even include the 3G PPP interface whenever it came up, and that only came up when we manually instructed it to connect as it cost money).
Not saying this isn't good software, but it's by far not the problem the summary purports it to be, not a first by any means, and certainly not "new".
Re:Strange (Score:5, Informative)
Think it was:
http://www.ssi.bg/~ja/ [www.ssi.bg]
Seems to still be updated.
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I wonder how this is different from channel bonding / link aggregation? I looked into this a few months ago and don't remember all the details but there's a "bonding" kernel module, which can run in some modes entirely in kernel space, or in a user-space-assisted mode. There is a round-robin mode but there are several others that include fault tolerance and load balancing. LACP can be used in cooperation with other network elements including switches if you want something that spans a local network.
I had li
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LACP would, indeed, fulfill the purpose but relies on you being able to obtain LACP support on upstream connections from your ISP. LACP must be enabled and known about on both ends for it to do anything.
It's not always true that you could get support on upstream connection, but they are many, and multiple, types of bonding that provide similar facilities.
However, in terms of being able to get disparate connections that can be conjoined without specific support on the other end or high-end hardware, there a
Re:Strange (Score:5, Informative)
Multipath routing works at layer 3 (e.g. IP), you can send outbound packets to multiple routers for further forwarding. It works when there are "real" routes between the hosts (i.e. not behind NAT).
This is one step beyond that, since it also does connection tracking and will work with outbound port NAT, so you can have a private network connected to multiple ISPs.
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Re: Strange (Score:2)
Linux has been able do multipath routing for a long time: it means being able to have routes with multiple gateways and to use them in a (weighted) round-robin fashion. But Linux is missing a tool to actively monitor the state of internet uplinks and change the routing accordingly
No the author is lacking knowledge of such tools. There are at least three major implementations of common routing protocols for Linux.
It is actually surprisingly simple. You activate OSPF on your Linux box and it will add routes on working links and remove them again if the path is no longer viable. Works both ways too, so your routers will not try to deliver traffic to your box on a dead link. Instead the routers will route around the problem.
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I recommend you follow your own advice. Stop feeding the trolls.
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Ruby?? (Score:4, Insightful)
I do not want to install Ruby on my firewall/gateway along with all of its douchebaggy dependencies and gems/crystals/unicorns/whatever-the-fuck-they're-called. This is networking, not some hipster web 2.0 app.
Re:Ruby?? (Score:4, Informative)
It's really a glorified bash script..and it doesn't actually require any ruby gems to run.
It's just pinging a configurable IP to test specific outbound connections and when an interface goes up or down it resets the routing table...nothing especially fancy.
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https://github.com/drsound/fault_tolerant_router/blob/master/fault_tolerant_router.gemspec
At this time it installs at least one gem, and it looks like it's for sending mail (notifications). And that gem might have dependencies of its own.
Given time, and enough feature creep, this project very wall may require more gems down the line.
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At this time it installs at least one gem, and it looks like it's for sending mail (notifications). And that gem might have dependencies of its own.
Given time, and enough feature creep, this project very wall may require more gems down the line.
D'oh...You're right..I scanned the gemspec and missed the runtime one below the dev ones.
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Ruby is an excellent scripting language, equivalent to Perl or Python... better in some ways, worse in others. Nobody bats an eye if something requires Perl, even though CPAN Gems are essentially equivalent.
Ruby != Rails.
Re:Ruby?? (Score:5, Informative)
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Then, mr hardtoplease, wait for the systemd based implementation, it is right around the corner (holding a knife).
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remote video streaming (Score:2)
I am unclear if this would work for a "single stream" like a video webcast source in a remote location using multiple cellular links like jetpacks. I can easily see how any given network request would go to one link or another depending on availability, but I'm assuming that this would not be able to take a network video stream and parse out portions of it to the various uplinks and then at the far end put the stream back together (in order to get either extra bandwidth or extra reliability) to forward on
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I think the logic for streaming would just be too complicated over multiple links. You might make it work if you had a proxy that knew about the links and had some way to choose paths, but you'd still have to work out the application layer bit to negotiate the paths with the streaming source so it could send them down multiple paths and then there would need to be some kind of ordering and link balancing on top of it.
I think the only way to make it work with a stream is something like you've outlined -- an
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marking packets (Score:2)
I would be happy enough if I figured out how to mark the packets so that my routing actually works. I already have a shell script to switch connection from fiber to 3g, but incoming connections only work on one at a time. However, I'm not willing to run Ruby on my router to solve that issue...
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Zebra (Score:2)
That's one of the points of zebra and the suite of tools that it brings to the table.
The kernel shouldn't do more than it already does unless you want to move the kernel into systemd as well.
http://en.wikipedia.org/wiki/G... [wikipedia.org]
Zebra is not, by any means, new.
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Oh hell, this story is nothing more than a slashvertisement for some guys new pet project, the first commit is barely 2 weeks old.
Could you people use google and a cloupon before you reinvent the wheel using a shitty scripting language, please.
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unless you want to move the kernel into systemd as well.
Shhhhh...you're giving them ideas.
Done in bash since the 2000s (Score:2)
But hey, it hasn't been on Github until now. Why the hell is this news?
OpenWRT with mwan3 (Score:5, Informative)
OpenWRT package mwan3 has similar functionality without the complication of multipath.
http://wiki.openwrt.org/doc/ho... [openwrt.org]
Not to lose my karma (Score:3, Insightful)
Many other tools for multipath (Score:5, Informative)
There's a lot of multipath-related work being done right now, at the IETF, within OpenWRT, and independently.
We've been working on providing multiple routes automatically [arxiv.org] (disclaimer -- I'm a co-author). As to actually making use of the multiple routes, the solution that currently works best is MP-TCP [multipath-tcp.org], a set of kernel patches that allows TCP to use multiple routes simultaneously, with no modification to applications. Other solutions are SHIM6 [wikipedia.org], which works below the transport layer, and Multipath Mosh [arxiv.org], which works at the application layer.
I'm pretty confident we'll be able to have most of this stuff enabled by default in mainstream Linux distributions by the end of the year.
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Well, this example is just a simple load balancing with outbound NAT and nothing as fancy as the stuff you cited which aims for e.g. multipathing single sessions like MPTCP does.
Been working on that same area.
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Indeed, I have many times run a linux router by doing nothing but installing quagga, Net-SNMP, ipt_netflow, and I've got a lower end equivalent to some of the highest end commercial networking equipment.
Both OSPF and BGP provide the tools you need for policy based routing to various degrees, and quagga gives you that. The rest is just icing on the cake.
gwping (Score:3, Interesting)
There is a small shell script called gwping, which can be used to do the exactly same thing, easier and simpler. It's ~150 lines (with comments and everything) and takes 10-20 minutes to setup with the policy routing and everything, we don't need an overbloated runtime to do something so simple.
There is a script for that... (Score:1)
dualgate_multinet.sh supports dual-gateways and multiple subnet vlans.
https://github.com/sodonnell/b... [github.com]
This script can easily be extended to support more than (2) gateways, and can support various VLAN/subnet configurations and isolation.
Shorewall and LSM have offered this for years (Score:2)
The hard part of the equation is your public DNS records that need to change to whichever IP address is "active" (or round-robin between the two). But most DNS service providers have a solution for that as well.
Naturally, it's not as seamless as multi-path, but i
A solution to a down interface (Score:1)
Iproute2 has worked out very well
Ruby... (Score:2)
Pity it's written in ruby, that's a bit too heavy for most small routers...