====== DSL and satellite links aggregation ======

The purpose of this document is to explain how to aggregate a DSL link (low latency, low bandwidth) with a satellite link (high latency, high bandwidth) to get the best parts of both solutions. Actually it's not a real "aggregation" method but it's rather a manual balacing depending on outgoing traffic.

===== Context =====

Living far away from the city and thus far away from a DSLAM, the DSL link I'm connected to doesn't allow decent bandwidth (**1.5 Mbits**/**768 Kbits**) but the latency is fine (∼ **30ms**). Current satellite internet rate plans can reach **20 Mbits**/**6 Mbits** with a round latency of **700ms**.

==== Why  more bandwidth ? ====

  * Having severals computers or devices is painful in case of software upgrades (occur pretty often)
  * Overall bandwidth is crawled when a computer/device is downloading
  * Sending files takes millions of years (remote backups, emails, etc) 
  * VOD with some TV related devices require a lot of bandwidth (> 5Mbits)

==== Why keeping a DSL link ? ====

  * Online gaming (MMORPG, FPS) needs a low latency
  * Vital network services (like DNS) run smoothly with a low latency. Performing DNS resolution with a DSL link should improve matters
  * Interactive services such as SSH and VPN can turn you mad with a too high latency but work great with a DSL link

Having 2 links allow to use failover in case one link is failing.

===== Cons =====

  * Price is high (one DSL and one satellite subscription)
  * Setting a parabola up is painful



===== Used software =====

To achieve this we use [[https://www.google.fr/#q=zeroshell|ZeroShell]]. It has tons of functionalities and especially handles multi WAN interfaces (with load balancing, failover and manual balancing). It's based on Linux and runs on many devices (PCs, Alix/Soekris boards, etc). Although it's live CD based profiles and parameters can be saved on hard drive, usb devices, CF/SD cards, etc. Specific hardware images are also available for download. A recent linux distro can do the job but you need to be familiar with advanced iptables configuration, routing, traffic classification, etc. ZeroShell makes life easier.

A Web GUI is available to perform all tasks (except Wireless). A console or SSH access is available anyway.

===== Used hardware =====

  * [[http://www.gooze.eu/alix-2d13-pc-engines-kit|Alix boards 2D3]] with 3 LAN interfaces and 1 mini PCI wireless adapter
  * 1 dsl modem (acting as a bridge and providing a WAN ip, let's say WAN_IP1 for later use)
  * 1 satellite modem (acting as a bridge and providing a WAN ip, let's say WAN_IP2 for later use)
  * At least one switch to connect the router to the LAN

=> ZeroShell supports PPPoE, 3G modems, etc

===== Architecture design =====

{{:informatique:reseau:zeroshell:net_balancer:drawing1.png?200|}}
{{:informatique:reseau:zeroshell:net_balancer:lan.png?700}}