Snom 4S Media Server Instruction Manual

F REQUENTLY
A SKED
Q UESTION
Mailbox Setup on the snom
4S Media Server
Date: Jan-21-2004
Author: Christian Stredicke
Document: faq-04-01-21-cs

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Mailbox Setup 3
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There are several ways to set up
mailboxes on the snom media server. This FAQ
should help you avoiding common pitfalls and
unnecessary overhead.
The settings shown in this FAQ should be
done by the administrator of the media server
and/or of the proxy. Of course, you should not
give end users access to the web page of the
media server.
Registering mailbox accounts
You should not register mailbox accounts.
Registering has the following disadvantages:
• Registering causes additional load for the
media server CPU. Especially when regis-
tering all accounts at the same time, this
might have negative effects on the respon-
siveness of the media server.
• Every registration possibly requires a li-
cense on the proxy.
You should also not redirect calls to the
mailbox using the SIP user agents. Typically,
the SIP UA is simply turned off (e.g. when
using a soft phone) and in this situation there
would be no device available that is actually
doing the redirect. The proxy will be available
all the time and its better if the proxy takes
care about redirecting calls to the mailbox.
4S Proxy Conguration for Directing
Calls to Voice Mail Accounts
Instead of registering mailbox accounts,
you can use the dial plan (or any other static
route) on the proxy to redirect calls to the
mailbox. For example, on the snom 4S proxy
you can use the dial plan entry Mode=Forward,
From=*, To=sip:9$$$@~*, Argument= sip:
{user}@media.company.com. When someone
calls a number starting with 9 (as indication
that the mailbox account should be called),
Figure 1: Typical settings on the snom 4S proxy

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the call gets routed to the media server. In this
example, it is expected that the account has
exactly three digits ($$$, the number of “$”
signs correspondents to the number of digits
for an account).
If you are using the above argument, the
accounts on the media server need to include
the prex number. If you want to change
this behaviour you can alternatively use the
argument sip:{user:1}.domain.com@medi
a.company.com, which will omit the leading
character; in this case the account on the
mailbox will have a name like the account on
the proxy.
In the above case, the proxy will look
up the DNS address media.company.com.
That means you will have to supply a DNS
entry for this address (according to RFC3263).
Of course, you can also use IP addresses
instead.
Figure 1 shows how to set up an individual
user account to redirect calls to a mailbox. The
proxy manual and the initial login screen of
the proxy explain how to reach the settings
web page for an user account.
In order to redirect call to the mailbox,
you need to ll in the Mailbox Number. Also,
it’s helpful to dene the mailbox timeout (the
default value is 20 seconds). It is enough to ll
in the “extension-number” style of the mailbox
account, because the proxy will redirect the
call to the right destination. This will especially
work if you are using the media server in the
context of several domains.
Reaching mailbox accounts
In the above example, the user just puts
a 9 in front of the account number to reach
the mailbox. This method can also be used if
the user wants to call his or her own mailbox.
Of course, the 9 can be changed to any other
pattern (some German operators choose 99).
This method does not support the usage
of alias names. If, for example an account
has the names “123” and “abc”, the mailbox
can only be reached by one of the names
(preferably the rst).
Multiple domain setup
Sharing a resource between different
domains is a known problem also from other
services. For example, when you want to get
your email from your service provider, you use
an email address like “stredicke%snom.de@i
sp.de”. The same mechanism can be applied
to mailbox accounts on the snom 4S media
server.
We propose to use a dot to separate the
account and the domain name. Using this
character minimizes the interoperability issues
because most implementations can deal with
this character. Mailbox names then look like
DNS names.
A sample dial plan entry for the snom
4S proxy would look like this: Mode=Forward,
From=*, To=sip:9$$$@~*, Argument=sip:
{user}[email protected].com.
Because the dial plan is local to a domain, you
can always replace the “domain.com” with the
actual domain name where the dial plan is
Figure 2: Typical setup for two domains

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Figure 3: Typical setup for a mailbox account in a multiple domain environment
used.
Sending MWI
When a mailbox received another
message, you usually want to send a message
waiting indication (MWI).
Unfortunately there is currently no MWI
RFC available, and the previous drafts changed
their message format in non-backward
compatible way. Please check the rmware of
the user-agent for the IETF draft version if you
experience trouble with MWI indications.
The snom media server (version 2.21)
uses http://www.ietf.org/internet-drafts/draft-
ietf-sipping-mwi-04.txt. Hopefully, future
drafts and the MWI RFC will be compatible
with this draft, so there will be no need to have
further software upgrades.
In principle, there are two ways to do this
from the media server:
• You can subscribe to the message-waiting-
event. This way, the subscribing user agent
explicitly tells the media server where to
send the events. This method requires that
the user agent supports MWI subscriptions
(like the snom VoIP phones). You may have
several subscriptions per mailbox without
any problem. This method has the advan-
tage that users receive an initial message
waiting indication when they log in. Howev-
er, the disadvantages are the subscription
trafc and the need to set up the subscrip-
tions on the endpoints.
• The media server has the destination ad-
dress of the user agent. This address is
typically the address of the user agents on
the proxy (with the account name in front
of the “at” symbol). The proxy will forward

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the request to registered user agents as
soon as the request arrives on the user
agent. In this case, you must specify the
plain name of the user account, not the
name if the mailbox account. If you use a
default domain on the media server, you
may use the short form for the destina-
tion (e.g. “123”). Otherwise, you need to
specify the SIP URI for the destination (e.g.
“sip:[e-mail]”).
Both methods can be mixed; however
we recommend the usage of the second
method. The second method needs a setup on
the media server; however it will make sure
that the message is sent to the destination
regardless of the user agent registering for
the event.
In future versions of the proxy we plan
to include a MWI web page which displays
the MWI to the user. It will also automatically
send the MWI event after the user agents
registers with the proxy. This will eliminate the
disadvantage of the second method against
the rst method. This new feature will also
deal with the incompatible versions between
the different MWI drafts.

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