VoIP is Voice Over Internet Protocol
voice based network
used communicate through IP

VoIP services convert your voice into a digital signal that
travels over the Internet. If you are calling a regular
phone number, the signal is converted to a regular telephone
signal before it reaches the destination. VoIP can allow you
to make a call directly from a computer, a special VoIP
phone, or a traditional phone connected to a special
adapter. In addition, wireless "hot spots" in locations such
as airports, parks, and cafes allow you to connect to the
Internet and may enable you to use VoIP service wirelessly.

Voice over Internet Protocol (VoIP), is a technology that
allows you to make voice calls using a broadband Internet
connection instead of a regular (or analog) phone line. Some
VoIP services may only allow you to call other people using
the same service, but others may allow you to call anyone
who has a telephone number - including local, long distance,
mobile, and international numbers. Also, while some VoIP
services only work over your computer or a special VoIP
phone, other services allow you to use a traditional phone
connected to a VoIP adapter.

VPN means Virtual Private Network
Take and example : Our one office is in USA and one in India
We have Hardware VPN over there and installed software VPN 
over here in India and implemented the policy file over 
here by this way we can connect to US office PC through VPN

A VPN connection is the extension of a private network that 
includes links across shared or public networks, such as 
the Internet. VPN connections (VPNs) enable organizations 
to send data between two computers across the Internet in a 
manner that emulates the properties of a point-to-point 
private link.

Basically, a VPN is a private network that uses a public 
network (usually the Internet) to connect remote sites or 
users together. Instead of using a dedicated, real-world 
connection such as leased line, a VPN uses "virtual" 
connections routed through the Internet from the company's 
private network to the remote site or employee. In this 
article, you will gain a fundamental understanding of VPNs, 
and learn about basic VPN components, technologies, 
tunneling and security.

VPN Virtual Private Network, A service which provides 
Secure network connectivity between two remote locations 
over a insecure network(internet/ISP).

The simple network management protocol (SNMP) use for 
monitoring of network-attached devices for any conditions 
that warrant administrative attention. It is use to manage 
IP network devices such as servers, routers, switches etc. 
Administrator can find or manage network performance, solve 
problem or even optimize it further. It works at TCP/IP 
Application layer 5 (L5

Use Simple Network Management Protocol (SNMP) management 
software to monitor any network device configured with SNMP 
agent software. The SNMP agent, which is an optional 
component of Windows Server 2003, interacts with third-
party SNMP management software to enable the flow of 
network status information between monitored devices and 
applications and the management systems that monitor them.

You can use SNMP in environments that include large 
networks with hundreds or thousands of nodes that would 
otherwise be difficult and costly to monitor. SNMP allows 
monitoring of network devices such as servers, 
workstations, printers, routers, bridges, and hubs, as well 
as services such as Dynamic Host Configuration Protocol 
(DHCP) or Windows Internet Name Service (WINS).

acces list for use the perticular using the acess network

Access lists controls the traffic flow between the routers 
its a layer three security and is also called as packet 
filtering firewall 
Access lists are of three types
1.Standard access list
2.Extended access list
3.Named access list

1.standard access list : 

acl no lies between 1-99
Let us say two routers are there and you want to block 
packets from a network or a host or from a particular 
subnet it can be impelemented using standard access list 
but the disadvantage is at the same time even you are 
unable to send the data to that particular network or to 
host or to that subnet ,..means two way communication is 
stopped and it is to be implemented at your end means at 
destination end 

2.Extended access List :

acl no lies between 100- 199
Extended access list also same as stnadard acl 
except ..only one way communication is stopped means 
evanthough you are unable to receive the packets from 
paticular source you can send the packets to that 
particular source and one more major diff is it is 
implemented at the source end and one more advantage 
is we can block particular services like http.ftp,snmp etc 

Sorry i dont know much abt named access list :)