What is a "realm" and what is the
difference between a vISP using a "shared"
realm verses a "private" realm?
Although the word "realm" has several
meanings, when used in the internet access
business, it really has only one. In this case,
a realm is a usergroup name that is registered with a network, just as a
domain name is registered with a registrar. When
a subscriber of an ISP or virtual ISP attempts
to log on to the internet, the network checks to
see if they are using a realm (usergroup) authorized to
their network. If the realm is unauthorized, it
is immediately blocked. However, if it is an
authorized realm, the network then checks with
the ISP or vISP to see if the individual user is
authorized to log on. If they are not, they are
then blocked at this point. If their account is
in good standing access is given. All of this
takes place in milliseconds.
Most ISPs use use their domain
name for a realm, although this is not a
requirement. If they use their own name, they
are using a "private" realm. Their ISP and only
their ISP has this realm. However, network
providers charge to register a realm (as high as
$500) and additionally, UUNet charges a
$150/month realm charge. If a vISP is using many
networks, this can become quite costly.
Often times a vISP Provider (an ISP that
offers virtual ISP services) registers a generic
realm with all of the networks and allows their
virtual ISPs to share it. This is called a
"shared" realm. As in the case of Alliance
Solutions, we contract with between 25-30
different networks in order to have the largest
nationwide system footprint of all vISP
Providers. As you can imagine, registering a
realm with this many networks is quite expensive
for a start-up vISP. Although we will
register a private realm for vISP that desires
it, we also share our generic realm of "isp.us."
This saves our virtual ISPs thousands of
start-up dollars with which they can better use
To better understand this, let's use the
example of a vISP that with the domain name
With a "private" realm, this vISP's website
would reside at
www.acme.com, the subscribers' email would
email@example.com and the subscriber's logon
username would be
firstname.lastname@example.org. Now if Acme wanted to
save a lot of money in realm registration costs,
they would use a shared realm. With a "shared"
realm, the vISP's website would still be at
the subscribers' email would still be at
email@example.com, but the logon username
firstname.lastname@example.org. So the only difference
to the subscriber is their logon username.
So which is preferable?
The biggest reason to use a private realm is
simply that the logon username is the same as
the user's email address. So it is easier to
remember. However, most subscribers save their
logon username and password and never have a
need to remember it anyway.
A shared realm offers several
advantages for a vISP:
- It saves a lot of start-up
vISP Provider adds new networks, the vISP
automatically has access to them. With a private
realm, they must register their realm with the
network before being given access.
vISP desire to move their subscriber base to
another provider, the subscriber will only need
to change their logon username. In the case of a
private realm, the realm must be moved, just as
a domain is moved when a website is moved to a
different host. Although moving the realm is
easier for the vISP, there is a period of time
(up to 72 hours) while the realm is being
transferred that the subscriber will not be able
to access the internet at either provider.
So although Alliance provides both private
and shared realms, because of the advantages
mentioned above, we almost always recommend a