Point of presence (POP) refers to the network interface where a telephone company hands off its service to a subscriber. An Internet service provider (ISP) offers customers access to the Internet by connecting to them using technologies like dial-up, DSL, cable modem or wireless. Traffic moves over the Internet through ISPs, with the ISP connecting customers and routing packets between points of presence and allowing services like email and web access.

1. How Traffic Moves over the Internet
・point of presence (POP)
・Internet service provider (ISP)
・Routed Internet Access - Centrally Configured
・sending and receiving e-Mail

2. point of presence (POP)
Point or network interface which a telephone
company hands off its service to the
subscriber at. Equipment on the outer side of
the POP belongs to the telephone company,
and that on the other side to the consumer.

3. Internet service provider (ISP)
An Internet service provider (ISP), also sometimes referred to
as an Internet access provider (IAP), is a company that offers
its customers access to the Internet. The ISP connects to its
customers using a data transmission technology appropriate
for delivering Internet Protocol packets or frames, such as
dial-up, DSL, cable modem, wireless or dedicated high-speed
interconnects.

4. Routed Internet Access - Centrally Configured
The above diagram shows a cell (point to multi-point) configuration in which the Air-
Frame unit at the ISP premises is configured to control all network access. This diagram
contrasts with a Distributed or Customer Controlled Routed network. The use of the
DHCP function is not essential to the above operation but is shown to illustrate Air-
Frame functionality and versatility. a separate DHCP server could be used or each PC
could be separately configured. Similarly the use of a Proxy and Private IP addresses is
not essential. Air-Frame routers support static and dynamic addresses. A single Air-
Frame 100 can be configured to handle up to 64 separate customer locations. The Air-
Frame may be configured to periodically authenticate connections using a RADIUS
Server. Firewall functions may be located with the Proxy. The customer located Air-
Frame may be configured as a Router or a Bridge.

5. sending and receiving e-Mail
Like all other Internet users, you connect to
the Internet through your ISP.
All websites, including yours, reside on a host
server. When someone accesses any website,
the host server sends the website
information through the Internet, through
the user's ISP, and to the user's computer.
Everything your computer sends to and
receives from the Internet goes through your
ISP. This includes e-mail. When you send e-
mail using an e-mail client like Outlook, etc.,
it is sent from your computer, through your
ISP, to the Internet, to then be delivered
through the recipient's ISP to the recipient's
computer.
If you receive e-mail through your website,
this e-mail is stored on the host's mail server
until you retrieve it.

6. Reference
・Internet service provider
http://en.wikipedia.org/wiki/Internet_service_provider
・Business Dictionary.com
http://www.businessdictionary.com/definition/point-of-presence-POP.html
・Westone Corporation
http://www.westone.com.cn/english/view31.htm
・Steam Packet Radio
http://www.zytrax.net/solutions/isp/routed_central_access.htm