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Q: Cross connected VPN and Exchange ( No Answer,   3 Comments )
Subject: Cross connected VPN and Exchange
Category: Computers
Asked by: bvandyk-ga
List Price: $5.00
Posted: 14 Oct 2006 07:17 PDT
Expires: 13 Nov 2006 06:17 PST
Question ID: 773398
I have an issue with exchange mailboxes being very slow to operate
over a VPN connection.

We have 3 sites - all with exchange server on site, Site A, B & C.
Site A hosts Mr Smiths mailbox. It is hosted there as he is most often
based at Site A. When the user logs onto to outlook at site B the
mailbox is very slow to open and causes problems (e.g. hanging).

Site A has a VPN connection to C and Site B has a connection to site C
(like a triangle). But A and B are not connected directly. Can this
situation be resolved by adding another VPN connection on the Vigor
router (i.e. create a VPN from A to B) or will this not work?

There is no answer at this time.

Subject: Re: Cross connected VPN and Exchange
From: hadak-ga on 15 Oct 2006 14:18 PDT

That's a very good question!  First of all, i suppose it really
depends on your bandwidth and network saturation.  If you have 100
users at each site on DSL or cable, it's going to be extremely slow
going from site A to site B via vpn.  If you have only a few people
(10-20) per site, and a similar connection, the system will feel much
faster.  If these are internet connected machine (as i'm assuming they
are) then you can try hamachi (it's free - to see if
it solves your problem before spending money on a new vpn line.  If
you are on a closed WAN, this will not work.

In summary, I suggest trying hamachi (internet premitted) before
making any rash decisions.  Assuming your network is saturated, the
best option after that would be installing another VPN line.

I hope this answered your question.

Subject: Re: Cross connected VPN and Exchange
From: fabio1-ga on 18 Oct 2006 14:56 PDT
it should help, because it's one hop less that the mails have to jump
in order for them to get to Mr. Smith. You can test it by measuring
ping times directly between A and B versus A to B to C. Be sure to set
the packet size to 1500 using the -l option in windows, otherwise it
won't be a "good" test.

Other tip:
if you're not using outlook 2003, this may be a good time to upgrade.
It has a feature called cached mode, where the user's mailbox is
mirrored and stored in a local file (something.ost). So when Mr
Smith's goes to site B, he'll only download the mails he hasn't read
yet, and reading the rest of the mails is pretty fast, because
everything is cached.

I tested it in a branch office with 128k link over a vpn and it still
was very acceptable (and the dozen people that work there never
complained too). I also tested removing the cache, and it made a huge
Subject: Re: Cross connected VPN and Exchange
From: fluoro-ga on 21 Oct 2006 07:12 PDT
Hi, first of all, it is "normal" that the connection to the exchange
server from stie B is slow. This is due to the communication protocol
overhead that exchange client uses (RPC).

here's a quote from Microsoft:
"It is a full MAPI client that uses protocols such as RPC. It
generally assumes a high connectivity network such as a LAN, although
it is possible to support users over slower links if you consider the
ratio of scalability to available bandwidth"

Creating a VPN connection between site A and B won't speed things up
enough, due to protocol limitation. What I suggest to you in order of
preference, is:

1. Use outlook web Access for this user.
2. Use Outlook 2003, which operates in cached mode.
3. Use IMAP protocol for this user. Imap has almost every
functionalities of exchange, plus it runs very well over the internet.
4. Use standard POP connection.

Hope it helps

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