OSI DOD
Application, Presentation, Session Process/Application
Transport Host-to-Host
Network Internet
Data Link, Physical Network Access

Three-way handshake: SYN, SYN/ACK, ACK

req - request res - response

octet

virtual IP

Regional Registry Coverage Map

ARIN LACNIC AFRNIC RIPENCC APNIC

ifconfig: inet addr:10.0.0.130 Bcast:10.0.255.255 Mask:255.255.0.0

route: 10.0.0.0 * 255.255.0.0 U 0 0 0 eth0 127.0.0.0 * 255.0.0.0 U 0 0 0 lo

Notice, no gateway, means no internet. Only can work with others in the local network. As such you can add a gateway to connect it to the internet. A gateway that is already connected to the internet that is.

To turn on:

/sbin/route add default gw 10.0.0.1
/sbin/route

To delete:

/sbin/route del default

Another way to turn on the gateway:

/sbin/ifconfig eth0 10.0.0.252 netmask 255.255.0.0
/sbin/ifconfig eth0

To turn off:

/sbin/ifconfig eth0 down

cat /etc/sysconfig/network-scripts/ifcfg-eth0

/etc/host.deny host.deny vs iptables Completely different, since they focus on different layers.

hosts.deny is the service layer while iptables is the routing layer. iptables will block packets of any kind. hosts.deny will depend on specific services querying it. You can run a computer without inetd but it will only prevent / allow access to services, it won’t filter pings or other concepts. Also not everything honors hosts.deny. With iptables, it has no choice. iptables is at the routing layer, before the application sees the traffic. Packets has to go through iptables before the apps even sees them. Think of iptables as a firewall while hosts.deny as a do not allow list that some apps may follow.

Wireless Network

Spec Dist Speed Freq
802.11a 30m 54 Mbps 5GHz
802.11b 100m 11 Mbps 2.4 GHZ
802.11g 100m 54 Mbps 2.4 GHZ
802.11n 125m 100 Mbps+ 2.4/5GHz

Going from 28 kbps dialup to easily 10 mbps cable modem. And you don’t even need a telephone anymore.