IT 210:Web-based IT

Fall 2012IP Address Details & HTTP

Protocol

IP Address Details

Refresher…

What function do IP Addresses serve?

IP Addresses Composed of 2 parts: network ID (prefix assigned

by ISPs) and host ID (suffix assigned by local sysadmin)

IPv4 addresses consist of 4 octets How much of the IP address is used as a network

ID?

216.24.63.132

Assigning IP Addresses

Classful IP Address Assignment

IP address classes (32 bits = v4)

Class Leftmost bits

Start address

Finish address

Net bits Host bits

A 0xxx 0.0.0.0 127.255.255.255

7 24 (16M)

B 10xx 128.0.0.0 191.255.255.255

14 16 (65K)

C 110x 192.0.0.0 223.255.255.255

21 8 (256)

D 1110 224.0.0.0 239.255.255.255

multicast

E 1111 240.0.0.0 255.255.255.255

experimental

Many exceptions 127.0.0.0 -127.255.255.255 = loopback

127.0.0.1 = “home” or localhost Private addresses (see table)

Class Private start address Private end address

A 10.0.0.0 10.255.255.255

B 172.16.0.0 172.31.255.255

C 192.168.0.0 192.168.255.255

Script Kiddies

CIDR (Classless Inter-Domain Routing) The “prefix” (ironically shown after the

IP address) indicates how many bits in the Network ID. E.g., 192.168.0.0/16

CIDR & # of Hosts/13 524,288 /14 262,144 /15 131,072 /16 65,536 /17 32,768 /18 16,384 /19 8,192 /20 4,096 /21 2,048 /22 1,024 /23 512 /24 256 /25 128 /26 64 /27 32

Dynamic vs Static IP Addresses Static vs Dynamic

IP4 vs IP6 In Jan 2011 we ran out of IPv4 addresses.

IP4: 32-bit address 4.2 billion addresses available (232) 10.8.240.2

IP6: 128-bit address 3.4 x 1038 addresses available (2128) 2001:0f68:0000:0000:0000:0000:1986:69af which

condenses to 2001:f68::1986:69af

Aside: What is an RFC?

RFC “Request for Comment” Modern RFCs are NOT requesting comments

(Draft docs are used for that) Standards, informational, and other stuff Published by IETF

IETF = Internet Engineering Task Force

References RFC 1518 - An Architecture for IP Address

Allocation with CIDR RFC 1519 - Classless Inter-Domain Routing

(CIDR): an Address Assignment and Aggregation Strategy

RFC 2373 - IP Version 6 Addressing Architecture

Questions… True or False: The classless inter-domain

routing (CIDR) system helps assure that fewer IP addresses are “wasted”.

True or False: When I switch networks my IP address will also need to change.

How many unique IP addresses are there in IP4 and IP6?

Open up command-line… Type in ipconfig Now try ipconfig /all

Compare the IP address to what you find here: http://www.whatismyip.com

Try this again at home. Will it be different?

HTTP

See online tutorial http://www3.ntu.edu.sg/home/ehchua/

programming/webprogramming/HTTP_Basics.html