2 - Raspberry PI Community Projects

GOING FURTHER
Optimal configuration
The /usr/share/doc/wondershaper/README.Debian.gz file describes, in some
detail, the configuration method recommended by the package maintainer. In
particular, it advises measuring the download and upload speeds so as to best
evaluate real limits.
10.3.2.2. Standard Configuration
Barring a specific QoS configuration, the Linux kernel uses the pfifo_fast queue scheduler,
which provides a few interesting features by itself. The priority of each processed IP packet
is based on the ToS field (Type of Service) of this packet; modifying this field is enough to take
advantage of the scheduling features. There are five possible values:
• Normal-Service (0);
• Minimize-Cost (2);
• Maximize-Reliability (4);
• Maximize-Throughput (8);
• Minimize-Delay (16).
The ToS field can be set by applications that generate IP packets, or modified on the fly by
netfilter. The following rules are sufficient to increase responsiveness for a server's SSH service:
iptables -t mangle -A PREROUTING -p tcp --sport ssh -j TOS --set-tos Minimize-Delay
iptables -t mangle -A PREROUTING -p tcp --dport ssh -j TOS --set-tos Minimize-Delay
10.4. Dynamic Routing
The reference tool for dynamic routing is currently quagga, from the similarly-named package;
it used to be zebra until development of the latter stopped. However, quagga kept the names
of the programs for compatibility reasons which explains the zebra commands below.
BACK TO BASICS
Dynamic routing
Dynamic routing allows routers to adjust, in real time, the paths used for
transmiing IP packets. Each protocol involves its own method of defining
routes (shortest path, use routes advertised by peers, and so on).
In the Linux kernel, a route links a network device to a set of machines that
can be reached through this device. The route command defines new routes
and displays existing ones.
Quagga is a set of daemons cooperating to define the routing tables to be used by the Linux
kernel; each routing protocol (most notably BGP, OSPF and RIP) provides its own daemon. The
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