Open Systems Interconnection ( OSI ) is a standard reference model for communication between two end users in a network. The model is used in developing products and understanding networks.OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lower three layers are used when any message passes through the host computer. Messages intended for this computer pass to the upper layers. Messages destined for some other host are not passed up to the upper layers but are forwarded to another host.
Layer 1: The physical layer ...
This is the level of the actual hardware. It defines the physical characteristics of the network such as connections, voltage levels and timing. This layer conveys the bit stream through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier.
Layer 2: The data-link layer ...In this layer, the appropriate physical protocol is assigned to the data. Also, the type of network and the packet sequencing is defined.This layer provides synchronization for the physical level and does bit-stuffing for strings of 1's in excess of 5. It furnishes transmission protocol knowledge and management.
Layer 3: The network layer ...he way that the data will be sent to the recipient device is determined in this layer. Logical protocols, routing and addressing are handled here. This layer handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level). The network layer does routing and forwarding.
Layer 4: The transport layer ...This layer maintains flow control of data and provides for error checking and recovery of data between the devices. Flow control means that the Transport layer looks to see if data is coming from more than one application and integrates each application's data into a single stream for the physical network. This layer manages the end-to-end control (for example, determining whether all packets have arrived) and error-checking. It ensures complete data transfer.
Layer 5: The session layer ... It establishes, maintains and ends communication with the receiving device. This layer sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end. It deals with session and connection coordination.
Layer 6: The presentation layer ...It takes the data provided by the Application layer and converts it into a standard format that the other layers can understand. This is a layer, usually part of an operating system, that converts incoming and outgoing data from one presentation format to another (for example, from a text stream into a popup window with the newly arrived text). Sometimes called the syntax layer.
Layer 7: The application layer ...This is the layer that actually interacts with the Operating System or application whenever the user chooses to transfer files, read messages or perform other network-related activities. This is the layer at which communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. (This layer is not the application itself, although some applications may perform application layer functions.)
Layers 1 - 4 are called as "Transport Set" and Layers 5 to 7 are called as "Application set".

To know which protocols are being used in different layers we can see in the following link.
Wonderful chart describing relation between all protocols
Protocols in different Layers

What is HTTP Protocol ?
Hyper Text Transfer protocol - HTTP.
HTTP is a communication protocol to transfer data/information in network.
HTTP runs on top of TCP/IP.Immediate valid question is what is TCP and what is IP.
Both are simple protocols again.
TCP(Transmission controll protocol) is responsible for making sure that the file sent from one network node to another ends up as complete file at destination.
IP(Internet Protocol) is responsible for moving the file/chunks(file split into small packets) or routing the chunks from node to destination.
So HTTP is a protocol having Web-specific features but depends on TCP and IP to get complete request and responce from one to another nodes.
The structure of HTTP is a simple request/responce sequence; a browser(mozilla) requests and a server(apache) responds.
HTTP is IETF standard,RFC 2616.
HTTP protocol has several methods like POST,GET,PUT,TRACE,DELETE etc.
HTTP is a stateless protocol, due to this hosts will not be having information about users between requests. Session will not be maintained, so developer has to write code separately to maintain the session state of user separately.
There are 4 versions released till now.(HTTP 0.9, 1.0, 1.1, 1.2).

Subnetting concepts are always tricky to me ...when I go through I understand very clearly but when comes to practice I confused many times ...hence I generally refer ones the following link always before giving subnet ranges ...
Why subnetting ?
Subnetting
More abt subnetting
Basics and depth abt subnetting - Detailed explanation
Subnetting Tutor by CISCO
Many people who works in telecoms domain will face a situation to know the Possible IP ranges for a given subent.
So The following link surely helps people in calculating the
Subnet Mask,IP range etc.
N/W Calculator
IP Calculator

My Subnetting Example :

Problem :
We have been allocated a 130.16.0.0 IP address for our network. We wish to subnet this into 13 subnets and allow for the expansion in the near future. ?
Devise an IP subnet plan, giving the network, first host, last host and broadcast IP addresses for each subnet. Also specify the subnet mask you would use.


1. Calculate required number of bits to borrow for subnetting.
130 is a class B address so we can borrow from 2 to 14 bits
4 bits borrowed give us (24-2 ) = 14 subnets (not much room for expansion)
5 bits borrowed give us (25-2 ) = 30 subnets (plenty room for expansion)
So we choose to borrow 5 bits for the host part of the class B address.
This leaves 11 bits for hosts = 211-2 hosts = 2046 hosts per subnet (all 0’s and all 1’s cannot be used)
(In this question, the number of host required per subnet have not been specified (but they may be)!


2. Calculate the subnet mask

Subnet mask has all 1’s in the network+subnet part of the address.

Hence 11111111 11111111 11111000 00000000
= 255.255.248.0

3. Calculate all subnet network addresses

(in the 5 bits we have borrowed we count up sequentially from 00001 to 11110 (all 0’s and all 1’s cannot be used)
NB All 0’s in the host part refer to the subnet itself.

1st subnet = 130.16.00001 000.00000000 = 130.16.8.0
2nd subnet = 130.16.00010 000.00000000 = 130.16.16.0
3rd subnet = 130.16.00011 000.00000000 = 130.16.24.0
4th subnet = 130.16.00100 000.00000000 = 130.16.32.0
5th subnet = 130.16.00101 000.00000000 = 130.16.40.0
6th subnet = 130.16.00110 000.00000000 = 130.16.48.0
7th subnet = 130.16.00111 000.00000000 = 130.16.56.0
8th subnet = 130.16.01000 000.00000000 = 130.16.64.0
9th subnet = 130.16.01001 000.00000000 = 130.16.72.0
10th subnet = 130.16.01010 000.00000000 = 130.16.80.0
11th subnet = 130.16.01011 000.00000000 = 130.16.88.0
12th subnet = 130.16.01100 000.00000000 = 130.16.96.0
13th subnet = 130.16.01101 000.00000000 = 130.16.104.0
14th subnet = 130.16.01110 000.00000000 = 130.16.112.0
15th subnet = 130.16.01111 000.00000000 = 130.16.120.0
16th subnet = 130.16.10000 000.00000000 = 130.16.128.0
17th subnet = 130.16.10001 000.00000000 = 130.16.136.0
18th subnet = 130.16.10010 000.00000000 = 130.16.144.0
19th subnet = 130.16.10011 000.00000000 = 130.16.152.0
20th subnet = 130.16.10100 000.00000000 = 130.16.160.0
21th subnet = 130.16.10101 000.00000000 = 130.16.168.0
22th subnet = 130.16.10110 000.00000000 = 130.16.176.0
23th subnet = 130.16.10111 000.00000000 = 130.16.184.0
24th subnet = 130.16.11000 000.00000000 = 130.16.192.0
25th subnet = 130.16.11001 000.00000000 = 130.16.200.0
26th subnet = 130.16.11010 000.00000000 = 130.16.208.0
27th subnet = 130.16.11011 000.00000000 = 130.16.216.0
28th subnet = 130.16.11100 000.00000000 = 130.16.224.0
29th subnet = 130.16.11101 000.00000000 = 130.16.232.0
30th subnet = 130.16.11110 000.00000000 = 130.16.240.0

4 Calculate all address of the first host, last host and broadcast on each subnet.

First host is 1 in the host ID field (11 bits) = 000 00000001
Last host is 1 less than all 1’s in the host ID field (11 bits) = 111 11111110
Broadcast is all 1’s in the host ID field (11 bits) = 111 11111111

1st subnet =130.16.00001 000.00000000 = 130.16.8.0
First Host =130.16.00001 000.00000001 = 130.16.8.1
Last Host =130.16.00001 111.11111110 = 130.16.15.254
Broadcast =130.16.00001 111.11111111 = 130.16.15.255

2nd subnet =130.16.00010 000.00000000 = 130.16.16.0
First Host =130.16.00010 000.00000001 = 130.16.16.1
Last Host =130.16.00010 111.11111110 = 130.16.23.254
Broadcast =130.16.00010 111.11111111 = 130.16.23.255

3rd subnet =130.16.00011 000.00000000 = 130.16.24.0
First Host =130.16.00011 000.00000001 = 130.16.24.1
Last Host =130.16.00011 111.11111110 = 130.16.31.254
Broadcast =130.16.00011 111.11111111 = 130.16.31.255

4th subnet =130.16.00100 000.00000000 = 130.16.32.0
First Host =130.16.00100 000.00000001 = 130.16.32.1
Last Host =130.16.00100 111.11111110 = 130.16.39.254
Broadcast =130.16.00100 111.11111111 = 130.16.39.255

5th subnet =130.16.00101 000.00000000 = 130.16.40.0
First Host =130.16.00101 000.00000001 = 130.16.40.1
Last Host =130.16.00101 111.11111110 = 130.16.47.254
Broadcast =130.16.00101 111.11111111 = 130.16.47.255

6th subnet =130.16.00110 000.00000000 = 130.16.48.0
First Host =130.16.00110 000.00000001 = 130.16.48.1
Last Host =130.16.00110 111.11111110 = 130.16.55.254
Broadcast =130.16.00110 111.11111111 = 130.16.55.255

7th subnet =130.16.00111 000.00000000 = 130.16.56.0
First Host =130.16.00111 000.00000001 = 130.16.56.1
Last Host =130.16.00111 111.11111110 = 130.16.63.254
Broadcast =130.16.00111 111.11111111 = 130.16.63.255

8th subnet =130.16.01000 000.00000000 = 130.16.64.0
First Host =130.16.01000 000.00000001 = 130.16.64.1
Last Host =130.16.01000 111.11111110 = 130.16.71254
Broadcast =130.16.01000 111.11111111 = 130.16.71.255

9th subnet =130.16.01001 000.00000000 = 130.16.72.0
First Host =130.16.01001 000.00000001 = 130.16.72.1
Last Host =130.16.01001 111.11111110 = 130.16.79.254
Broadcast =130.16.01001 111.11111111 = 130.16.79.255

10th subnet =130.16.01010 000.00000000 = 130.16.80.0
First Host =130.16.01010 000.00000001 = 130.16.80.1
Last Host =130.16.01010 111.11111110 = 130.16.87.254
Broadcast =130.16.01010 111.11111111 = 130.16.87.255

11th subnet =130.16.01011 000.00000000 = 130.16.88.0
First Host =130.16.01011 000.00000001 = 130.16.88.1
Last Host =130.16.01011 111.11111110 = 130.16.95.254
Broadcast =130.16.01011 111.11111111 = 130.16.95.255

12th subnet =130.16.01100 000.00000000 = 130.16.96.0
First Host =130.16.01100 000.00000001 = 130.16.96.1
Last Host =130.16.01100 111.11111110 = 130.16.103.254
Broadcast =130.16.01100 111.11111111 = 130.16.103.255

13th subnet =130.16.01101 000.00000000 = 130.16.104.0
First Host =130.16.01101 000.00000001 = 130.16.104.1
Last Host =130.16.01101 111.11111110 = 130.16.111.254
Broadcast =130.16.01101 111.11111111 = 130.16.111.255

14th subnet =130.16.01110 000.00000000 = 130.16.112.0
First Host =130.16.01110 000.00000001 = 130.16.112.1
Last Host =130.16.01110 111.11111110 = 130.16.119.254
Broadcast =130.16.01110 111.11111111 = 130.16.119.255

15th subnet =130.16.01111 000.00000000 = 130.16.120.0
First Host =130.16.01111 000.00000001 = 130.16.120.1
Last Host =130.16.01111 111.11111110 = 130.16.127.254
Broadcast =130.16.01111 111.11111111 = 130.16.127.255

16th subnet =130.16.10000 000.00000000 = 130.16.128.0
First Host =130.16.10000 000.00000001 = 130.16.128.1
Last Host =130.16.10000 111.11111110 = 130.16.135.254
Broadcast =130.16.10000 111.11111111 = 130.16.135.255

17th subnet =130.16.10001 000.00000000 = 130.16.136.0
First Host =130.16.10001 000.00000001 = 130.16.136.1
Last Host =130.16.10001 111.11111110 = 130.16.143.254
Broadcast =130.16.10001 111.11111111 = 130.16.143.255

18th subnet =130.16.10010 000.00000000 = 130.16.144.0
First Host =130.16.10010 000.00000001 = 130.16.144.1
Last Host =130.16.10010 111.11111110 = 130.16.151.254
Broadcast =130.16.10010 111.11111111 = 130.16.151.255

19th subnet =130.16.10011 000.00000000 = 130.16.152.0
First Host =130.16.10011 000.00000001 = 130.16.152.1
Last Host =130.16.10011 111.11111110 = 130.16.159.254
Broadcast =130.16.10011 111.11111111 = 130.16.159.255

20th subnet =130.16.10100 000.00000000 = 130.16.160.0
First Host =130.16.10100 000.00000001 = 130.16.160.1
Last Host =130.16.10100 111.11111110 = 130.16.167.254
Broadcast =130.16.10100 111.11111111 = 130.16.167.255

21th subnet =130.16.10101 000.00000000 = 130.16.168.0
First Host =130.16.10101 000.00000001 = 130.16.168.1
Last Host =130.16.10101 111.11111110 = 130.16.175.254
Broadcast =130.16.10101 111.11111111 = 130.16.175.255

22th subnet =130.16.10110 000.00000000 = 130.16.176.0
First Host =130.16.10110 000.00000001 = 130.16.176.1
Last Host =130.16.10110 111.11111110 = 130.16.183.254
Broadcast =130.16.10110 111.11111111 = 130.16.183.255

23th subnet =130.16.10111 000.00000000 = 130.16.184.0
First Host =130.16.10111 000.00000001 = 130.16.184.1
Last Host =130.16.10111 111.11111110 = 130.16.191.254
Broadcast =130.16.10111 111.11111111 = 130.16.191.255

24th subnet =130.16.11000 000.00000000 = 130.16.192.0
First Host =130.16.11000 000.00000001 = 130.16.192.1
Last Host =130.16.11000 111.11111110 = 130.16.199.254
Broadcast =130.16.11000 111.11111111 = 130.16.199.255

25th subnet =130.16.11001 000.00000000 = 130.16.200.0
First Host =130.16.11001 000.00000001 = 130.16.200.1
Last Host =130.16.11001 111.11111110 = 130.16.207.254
Broadcast =130.16.11001 111.11111111 = 130.16.207.255

26th subnet =130.16.11010 000.00000000 = 130.16.208.0
First Host =130.16.11010 000.00000001 = 130.16.208.1
Last Host =130.16.11010 111.11111110 = 130.16.215.254
Broadcast =130.16.11010 111.11111111 = 130.16.215.255

27th subnet =130.16.11011 000.00000000 = 130.16.216.0
First Host =130.16.11011 000.00000001 = 130.16.216.1
Last Host =130.16.11011 111.11111110 = 130.16.223.254
Broadcast =130.16.11011 111.11111111 = 130.16.223.255

28th subnet =130.16.11100 000.00000000 = 130.16.224.0
First Host =130.16.11100 000.00000001 = 130.16.224.1
Last Host =130.16.11100 111.11111110 = 130.16.231.254
Broadcast =130.16.11100 111.11111111 = 130.16.231.255

29th subnet =130.16.11101 000.00000000 = 130.16.232.0
First Host =130.16.11101 000.00000001 = 130.16.232.1
Last Host =130.16.11101 111.11111110 = 130.16.239.254
Broadcast =130.16.11101 111.11111111 = 130.16.239.255

30th subnet =130.16.11110 000.00000000 = 130.16.240.0
First Host =130.16.11110 000.00000001 = 130.16.240.1
Last Host =130.16.11110 111.11111110 = 130.16.247.254
Broadcast =130.16.11110 111.11111111 = 130.16.247.255

If below links are not working to download the files ..please drop me a mail so that I can send those docs through mail.
see my mail id the contact page

Networking Essentials
NMS EMS basics
EMS.pdf
snmp.pdf
snmp_overview.pdf