Thursday, October 06, 2011
iLearn Part 3
I started of comparing the OSI and TCP/IP standard, and how they relate to one another's respective layers and the fact that they are a suite of protocols not just a single one. This included the Application, Presentation and Session layers of the OSI model becoming just the Application layer in the TCP/IP model.
I then moved on to the IP address format, with it's 4 octets, each having the ability to range from 0 - 255 and that an IP address will come combined with a subnet mask, and typically a default gateway dragging it's heals also. That way if it's not local communication we're talking about the data can get to it's destination successfully :)
Adding to that I spent some time on the two address concept, which is the Network layers IP address and the Data Links Ethernet Mac Address (00ac:45ee:22ff) which is burnt in to each network card during the manufacturing stage.
From there led me on to some examples of local communications (on the LAN) and the dog barking .... sorry ARP'ing. (see Jeremy Ciora @ cbtnuggets for an explanation on that lol). Then communications off of the local networks, which means leaving the safety of the network you know and venturing out via the default gateway onto the scary wide area network, eeeek!
And finally to wrap up I covered the different classes of IP address. These being class A (1-126 in the first octet), B (128-191 in the first octet) & C (192-223 in the first octet), which you can identify from just looking at an IP address.
I did also touch upon both Private and Public IP addresses and how Network Address Translation (NAT) can be used, but that's for another time :)