Mitel SME Server V5 with ServiceLink Podręcznik Użytkownika Pobierz pdf (Strona 10)

Chapter 4. Your Internet Service Provider (ISP)

Your ISP is your connection to the Internet - it routes Internet data packets to and from your server. It also provides other essential services. This

section of the user’s guide reviews what ISPs offer and what the implications are in choosing among the various options available to you. While your

ISP can also assist you in selecting and arranging the right Internet services for your organization, it’s important to know the general range of

services available, since not all ISPs offer all services.

Warning

If you are operating the product in "server-only" mode, you will need to review your gateway/ﬁrewall documentation and perhaps consult

with your ISP regarding your conﬁguration. For example, depending on your plans for the server, your ISP may need to publish DNS

records associating your mail and/or web servers with your ﬁrewall IP address. You may also need to conﬁgure your ﬁrewall for port

forwarding of services.

In server-only mode, the single Ethernet connection to the local network is "trusted" as being secure and packet ﬁltering is disabled. For

that reason, a server-only server must always be behind a local ﬁrewall. You should not directly connect such a system to the Internet via

an Internet Service Provider.

4.1. Dedicated versus dialup connectivity

Connectivity, also referred to as Internet access type, refers to the physical connection between your site and your ISP. How you connect to your ISP

affects the speed of your Internet connection, which, in turn, impacts such things as how quickly your web site is displayed to visitors.

Dedicated connectivity refers to a full-time connection to your ISP. Although they are more expensive than the alternative, dedicated connections

are generally faster and allow you to use the full range of services on your server. There are several common types of dedicated connectivity. ADSL

provides relatively fast data transmission over phone lines. A cable connection links you to your cable company, which provides you with many

(though not all) of the same services as a traditional ISP. The speed of transmission over a cable network can vary widely (from quite fast to very

slow) based in part on the usage within your neighborhood.

If you have dialup connectivity, your server is not permanently connected to the Internet. Rather, it connects to your ISP over a phone line using a

modem or ISDN adapter. Because your connection to the Internet is not permanent, some of the services on your server cannot be provided to the

outside world. For example, having your server host your external company web site would create a problem because whenever your server was not

connected to the Internet, the web site would not be available. (However, it could certainly host an intranet web site because the local network would

always be connected.)

4.2. The IP address

An IP address is an identifying number assigned to all devices connected to the Internet, and is used in routing information from one device to

another. Like your phone number, your IP address enables other people to reach you. In our standard conﬁguration, your ISP only needs to allocate

one IP address for your network. It is assigned to your server, which will accept all the Internet data packets intended for your network and distribute

them to the appropriate computer - much like an ofﬁce receptionist is able to accept incoming calls and direct them to the appropriate extension.

4.2.1. Static versus dynamic IP addressing

A static IP address never changes. It is permanently assigned to your server by your ISP.

Note: Static IP addressing is preferable to dynamic IP addressing because it makes it easier for users on the Internet to connect to your services.

Dynamic IP address assignment means that your IP address is assigned to you only temporarily and may be changed by your ISP. This makes it

more difﬁcult to ensure continuity of service to your network. Consider again our telephone number analogy. When your telephone number changes,

you are able to place outgoing calls. However, until your new phone number is registered with Directory Services, other people are unable to look up

your new number and place calls to you. Similarly, whenever your IP address changes, a record associating your server with its new IP address must

be published with the equivalent of Directory Services (known as Domain Name Service or DNS) before incoming trafﬁc can ﬁnd you.

If your IP address is dynamically assigned and you have a dedicated connection to your ISP (for example, with a typical cablemodem), you may ﬁnd

it helpful to use a dynamic DNS service. We strongly recommend you review Appendix B: Dynamic DNS services for more information about this

worthwhile option.

Tip: ServiceLink subscribers will have all their DNS needs taken care of as part of the base package and can use either a static or dynamic

address without having to use an additional dynamic DNS service.

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