Hi,
For data ecapsulation, VPN relies on either of the
following technologies like GRE , IPSec, L2F,
PPTP and L2TP .  But, which of the above
technologies is popular ? If they vary based
on the requirements, can you pls lemme know
a document/link that maps the technologies
against the requirements w.r.t VPN ?

Thx in advans,
Karthik Balaguru

IPSec and PPTP are more popular. The PPTP is using for client to server. 
IPSec can be used as cleint to server or site to site VPN. This search 
result may help.

Virtual Private NetworksLearn about the Microsoft commitment to support VPN 
interoperability through standards such as L2TP/IPsec and PPTP. Connecting 
Remote Users to Your Network ...
      technet.microsoft.com/en-us/network/bb545442.aspx


-- 
Bob Lin, Microsoft-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on
http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on
http://www.HowToNetworking.com


"karthikbalaguru" <karthikbalaguru79@gmail.com> wrote in message 
news:390def23-0826-447f-9cec-4e8e0ab32e3d@u1g2000pre.googlegroups.com...
> Hi,
> For data ecapsulation, VPN relies on either of the
> following technologies like GRE , IPSec, L2F,
> PPTP and L2TP .  But, which of the above
> technologies is popular ? If they vary based
> on the requirements, can you pls lemme know
> a document/link that maps the technologies
> against the requirements w.r.t VPN ?
>
> Thx in advans,
> Karthik Balaguru 

On Dec 19, 10:22=A0pm, "Bob Lin \(MS-MVP\)" <nore...@chicagotech.net>
wrote:
> IPSec and PPTP are more popular. The PPTP is using for client to server.
> IPSec can be used as cleint to server or site to site VPN. This search
> result may help.
>

Thx for your response. But it seems that PPTP can support only one
tunnel at a
time for each user. Therefore, its proposed successor, L2TP (a hybrid
of PPTP
and another protocol, L2F ) can support multiple, simultaneous tunnels
for
each user.

So, shouldn't L2TP be popular ?

PPTP and L2TP are the layer 2 VPN technologies from CPE (customer
premise
equipment) to CPE. IPSec is the primary layer 3 VPN technology
providing a CPE
to CPE tunnel. Refer- http://www.networkdictionary.com/networking/vpn.php

Further from another link from internet, i found that it seems that
PPTP separates the control and data channels into control stream that
runs over
TCP and a data stream that runs over GRE (a less popular Internet
standard).
But, in contrast L2TP combines the control/data channels and uses
high-performance UDP. This makes L2TP more "firewall friendly" than
PPTP -- a crucial advantage for an extranet protocol -- since most
firewalls
do not support GRE.

So, i wonder how PPTP is popular compared to L2TP ?
Any ideas ?

Thx in advans,
Karthik Balaguru

On Sat, 19 Dec 2009 14:09:33 -0800, karthikbalaguru wrote:

> On Dec 19, 10:22 pm, "Bob Lin \(MS-MVP\)" <nore...@chicagotech.net>
> wrote:
>> IPSec and PPTP are more popular. The PPTP is using for client to
>> server. IPSec can be used as cleint to server or site to site VPN. This
>> search result may help.
>>
>>
> Thx for your response. But it seems that PPTP can support only one
> tunnel at a
> time for each user. Therefore, its proposed successor, L2TP (a hybrid of
> PPTP
> and another protocol, L2F ) can support multiple, simultaneous tunnels
> for
> each user.
> 
> So, shouldn't L2TP be popular ?
> 
> PPTP and L2TP are the layer 2 VPN technologies from CPE (customer
> premise
> equipment) to CPE. IPSec is the primary layer 3 VPN technology providing
> a CPE
> to CPE tunnel. Refer-
> http://www.networkdictionary.com/networking/vpn.php
> 
> Further from another link from internet, i found that it seems that PPTP
> separates the control and data channels into control stream that runs
> over
> TCP and a data stream that runs over GRE (a less popular Internet
> standard).
> But, in contrast L2TP combines the control/data channels and uses
> high-performance UDP. This makes L2TP more "firewall friendly" than PPTP
> -- a crucial advantage for an extranet protocol -- since most firewalls
> do not support GRE.
> 
> So, i wonder how PPTP is popular compared to L2TP ? Any ideas ?
> 
> Thx in advans,
> Karthik Balaguru

i don't know much about VPN, but i do believe it's a field
dominated by proprietary/gateway solutions: cisco vpn, intel vpn, ...

On 19 Dec, 22:31, goarilla <kevin.pau...@skynet.remove-this.be> wrote:
> On Sat, 19 Dec 2009 14:09:33 -0800, karthikbalaguru wrote:
> > On Dec 19, 10:22=A0pm, "Bob Lin \(MS-MVP\)" <nore...@chicagotech.net>
> > wrote:
> >> IPSec and PPTP are more popular. The PPTP is using for client to
> >> server. IPSec can be used as cleint to server or site to site VPN. Thi=
s
> >> search result may help.
>
> > Thx for your response. But it seems that PPTP can support only one
> > tunnel at a
> > time for each user. Therefore, its proposed successor, L2TP (a hybrid o=
f
> > PPTP
> > and another protocol, L2F ) can support multiple, simultaneous tunnels
> > for
> > each user.
>
> > So, shouldn't L2TP be popular ?
>
> > PPTP and L2TP are the layer 2 VPN technologies from CPE (customer
> > premise
> > equipment) to CPE. IPSec is the primary layer 3 VPN technology providin=
g
> > a CPE
> > to CPE tunnel. Refer-
> >http://www.networkdictionary.com/networking/vpn.php
>
> > Further from another link from internet, i found that it seems that PPT=
P
> > separates the control and data channels into control stream that runs
> > over
> > TCP and a data stream that runs over GRE (a less popular Internet
> > standard).
> > But, in contrast L2TP combines the control/data channels and uses
> > high-performance UDP. This makes L2TP more "firewall friendly" than PPT=
P
> > -- a crucial advantage for an extranet protocol -- since most firewalls
> > do not support GRE.
>
> > So, i wonder how PPTP is popular compared to L2TP ? Any ideas ?
>
> > Thx in advans,
> > Karthik Balaguru
>
> i don't know much about VPN, but i do believe it's a field
> dominated by proprietary/gateway solutions: cisco vpn, intel vpn, ...

No.

IPSEC is very widely used for infrastructure VPNs and is
not proprietary. Cisco interoperates with Checkpoint interoperates
with Draytek interoperates with OpenVPN ....... Never found
a problem in dozens of cases.

What is often proprietary are the VPN client solutions where
one of the VPN endpoints is an individual PC.

Cisco, Microsoft, Checkpoint all have their own proprietary
inplementations.

"goarilla" <kevin.paulus@skynet.remove-this.be> wrote in message 
news:4b2d5444$0$2856$ba620e4c@news.skynet.be...
> On Sat, 19 Dec 2009 14:09:33 -0800, karthikbalaguru wrote:
>
>> On Dec 19, 10:22 pm, "Bob Lin \(MS-MVP\)" <nore...@chicagotech.net>
>> wrote:
>>> IPSec and PPTP are more popular. The PPTP is using for client to
>>> server. IPSec can be used as cleint to server or site to site VPN. This
>>> search result may help.
>>>
>>>
>> Thx for your response. But it seems that PPTP can support only one
>> tunnel at a
>> time for each user. Therefore, its proposed successor, L2TP (a hybrid of
>> PPTP
>> and another protocol, L2F ) can support multiple, simultaneous tunnels
>> for
>> each user.
>>
>> So, shouldn't L2TP be popular ?
>>
>> PPTP and L2TP are the layer 2 VPN technologies from CPE (customer
>> premise
>> equipment) to CPE. IPSec is the primary layer 3 VPN technology providing
>> a CPE
>> to CPE tunnel. Refer-
>> http://www.networkdictionary.com/networking/vpn.php
>>
>> Further from another link from internet, i found that it seems that PPTP
>> separates the control and data channels into control stream that runs
>> over
>> TCP and a data stream that runs over GRE (a less popular Internet
>> standard).
>> But, in contrast L2TP combines the control/data channels and uses
>> high-performance UDP. This makes L2TP more "firewall friendly" than PPTP
>> -- a crucial advantage for an extranet protocol -- since most firewalls
>> do not support GRE.
>>
>> So, i wonder how PPTP is popular compared to L2TP ? Any ideas ?
>>
>> Thx in advans,
>> Karthik Balaguru
>
> i don't know much about VPN, but i do believe it's a field
> dominated by proprietary/gateway solutions: cisco vpn, intel vpn, ...
>

   I would say that PPTP maintains its popularity with small to medium sized 
organisations because it does not require certificates. If you have an 
established certificate system in your organisation (and a person capable of 
maintaining it), L2TP is the obvious choice.

   If you do not, setting up and maintaining this simply to support a few 
dialup VPN clients is a big ask. Making a few changes to your firewall for 
GRE is pretty minor by comparison.
 

On Sat, 19 Dec 2009 14:09:33 -0800 (PST), karthikbalaguru
<karthikbalaguru79@gmail.com> wrote:

>On Dec 19, 10:22�pm, "Bob Lin \(MS-MVP\)" <nore...@chicagotech.net>
>wrote:
>> IPSec and PPTP are more popular. The PPTP is using for client to server.
>> IPSec can be used as cleint to server or site to site VPN. This search
>> result may help.
>>
>
>Thx for your response. But it seems that PPTP can support only one
>tunnel at a
>time for each user. Therefore, its proposed successor, L2TP (a hybrid
>of PPTP
>and another protocol, L2F ) can support multiple, simultaneous tunnels
>for
>each user.
>
>So, shouldn't L2TP be popular ?
>
RFCs are written around standards, and IPsec is the one that gets
picked often :) 

I vaguely remember this is to do with the encryption setups since the
various L2 protocols seem to be less versatile. 

You need to remember VPNs are often specified by security depts, not
IP, so security can be considered more important than simplicity.

>PPTP and L2TP are the layer 2 VPN technologies from CPE (customer
>premise
>equipment) to CPE. IPSec is the primary layer 3 VPN technology
>providing a CPE
>to CPE tunnel. Refer- http://www.networkdictionary.com/networking/vpn.php
>
>Further from another link from internet, i found that it seems that
>PPTP separates the control and data channels into control stream that
>runs over
>TCP and a data stream that runs over GRE (a less popular Internet
>standard).
>But, in contrast L2TP combines the control/data channels and uses
>high-performance UDP. This makes L2TP more "firewall friendly" than
>PPTP -- a crucial advantage for an extranet protocol -- since most
>firewalls
>do not support GRE.
life as usual isnt that simple.

if you look at how IPsec is used in practice for "non single client"
setups you tend to get another protocol within the IPsec wrapper.

router to router links are often used in a resilient network - where
you want multicast then you get
IPsec -> GRE tunnel -> encap packet.

Where you have client PC style VPNs a different set of constraints
apply - 
Cisco VPN client on a PC is IPsec by default (last few times i used
it)., but if you want to get it thru a NAT based SOHO router, you
"hide" the IPsec by wrapping that in a UDP or TCP stream.

So you get UDP wrapper stream -> IPsec -> encap packet.

The TCP setup is a good fallback where the error handling is needed or
a firewall doesnt allow UDP.
So if you have a really poor link, or low thruput and high jitter such
as older 3G links then TCP encap instead of UDP.

Other VPN client setups seem to do similar things.

>
>So, i wonder how PPTP is popular compared to L2TP ?
>Any ideas ?
>
If you want simple then throw all the thick client stuff out and go
for SSL - but there are some apps that just do not work well or at all
in a web front end setup.

>Thx in advans,
>Karthik Balaguru
-- 
Regards

stephen_hope@xyzworld.com - replace xyz with ntl

Meanwhile, at the comp.dcom.sys.cisco Job Justification Hearings, bod43 
chose the tried and tested strategy of:

> Draytek interoperates with OpenVPN

OpenVPN is proprietary and will not work with a Draytek router. 

-- 
 <http://ale.cx/> (AIM:troffasky) (UnSoEsNpEaTm@ale.cx)
 09:47:26 up 22 days, 13:40,  8 users,  load average: 0.00, 1.02, 1.32
 Plant food is a made up drug

karthikbalaguru <karthikbalaguru79@gmail.com> wrote:
> On Dec 19, 10:22 pm, "Bob Lin \(MS-MVP\)" <nore...@chicagotech.net>
> wrote:
>> IPSec and PPTP are more popular. The PPTP is using for client to server.
>> IPSec can be used as cleint to server or site to site VPN. This search
>> result may help.
>>
>
> Thx for your response. But it seems that PPTP can support only one
> tunnel at a
> time for each user. Therefore, its proposed successor, L2TP (a hybrid
> of PPTP
> and another protocol, L2F ) can support multiple, simultaneous tunnels
> for
> each user.
>
> So, shouldn't L2TP be popular ?

I think you should know that "what is popular" is not determined by
what can do most, what is technically superior and other such reasons
that you run in to when you do a comparison of VPN technologies as
a technician.

What is popular is determined by what sells best, or what is part of
something that already sells best.  When it can do the job, it is used.

alexd wrote:

> Meanwhile, at the comp.dcom.sys.cisco Job Justification Hearings, bod43
> chose the tried and tested strategy of:
> 
>> Draytek interoperates with OpenVPN
> 
> OpenVPN is proprietary and will not work with a Draytek router.

OpenVPN community edition has been released under the GPL. Hardly 
proprietary. If it does not work, then hack on the source.

-- 
http://www.mailtrap.org.uk/

On 20 Dec, 09:50, alexd <troffa...@hotmail.com> wrote:
> Meanwhile, at the comp.dcom.sys.cisco Job Justification Hearings, bod43
> chose the tried and tested strategy of:
>
> > Draytek interoperates with OpenVPN
>
> OpenVPN is proprietary and will not work with a Draytek router.

OK. Was working by memory.

I recall now, maybe we passed OpenVPN through
our firewall and did not terminate on it. Sorry.

> On 19 Dec, 22:31, goarilla <kevin.pau...@skynet.remove-this.be> wrote:
>> On Sat, 19 Dec 2009 14:09:33 -0800, karthikbalaguru wrote:
>>> On Dec 19, 10:22�pm, "Bob Lin \(MS-MVP\)" <nore...@chicagotech.net>
>>> wrote:
>>>> IPSec and PPTP are more popular. The PPTP is using for client to
>>>> server. IPSec can be used as cleint to server or site to site VPN. This
>>>> search result may help.
>> 
>>> Thx for your response. But it seems that PPTP can support only one
>>> tunnel at a
>>> time for each user. Therefore, its proposed successor, L2TP (a hybrid of
>>> PPTP
>>> and another protocol, L2F ) can support multiple, simultaneous tunnels
>>> for
>>> each user.
>> 
>>> So, shouldn't L2TP be popular ?
>> 
>>> PPTP and L2TP are the layer 2 VPN technologies from CPE (customer
>>> premise
>>> equipment) to CPE. IPSec is the primary layer 3 VPN technology providing
>>> a CPE
>>> to CPE tunnel. Refer-
>>> http://www.networkdictionary.com/networking/vpn.php
>>> Further from another link from internet, i found that it seems that PPTP
>>> separates the control and data channels into control stream that runs
>>> over
>>> TCP and a data stream that runs over GRE (a less popular Internet
>>> standard).
>>> But, in contrast L2TP combines the control/data channels and uses
>>> high-performance UDP. This makes L2TP more "firewall friendly" than PPTP
>>> -- a crucial advantage for an extranet protocol -- since most firewalls
>>> do not support GRE.
>> 
>>> So, i wonder how PPTP is popular compared to L2TP ? Any ideas ?
>>> Thx in advans,
>>> Karthik Balaguru
>> 
>> i don't know much about VPN, but i do believe it's a field
>> dominated by proprietary/gateway solutions: cisco vpn, intel vpn, ...
>
> No.
>
> IPSEC is very widely used for infrastructure VPNs and is
> not proprietary. Cisco interoperates with Checkpoint interoperates
> with Draytek interoperates with OpenVPN ....... Never found
> a problem in dozens of cases.
>
> What is often proprietary are the VPN client solutions where
> one of the VPN endpoints is an individual PC.
>
> Cisco, Microsoft, Checkpoint all have their own proprietary
> inplementations.

I wouldn't say it's proprietary between Microsoft and Cisco, for after 
all, THEY developed L2TP as a joint venture, which became an industry 
standard.

L2TPIn order to make use of the features of both PPTP and L2F, L2TP was 
developed in a joint venture between Microsoft and Cisco. ...
http://zaielacademic.net/security/l2tp.htm

Some companies do have their own propietary stuff, such as OpenVPN, but 
I haven't used it, so I can't comment on it.

-- 
Ace

This posting is provided "AS-IS" with no warranties or guarantees and 
confers no rights.

Please reply back to the newsgroup or forum for collaboration benefit 
among responding engineers, and to help others benefit from your 
resolution.

Ace Fekay, MCT, MCITP EA, MCTS Windows 2008 & Exchange 2007, MCSE & 
MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer

For urgent issues, please contact Microsoft PSS directly. Please check 
http://support.microsoft.com for regional support phone numbers.

"Bill Grant" <not.available@online> wrote in message 
news:uMOaD0PgKHA.1112@TK2MSFTNGP04.phx.gbl...
>
>   I would say that PPTP maintains its popularity with small to medium 
> sized organisations because it does not require certificates. If you have 
> an established certificate system in your organisation (and a person 
> capable of maintaining it), L2TP is the obvious choice.

Could use a pre-shared key for the L2TP which is about like using a 
password.  However I just use PPTP being the small to medium size kinda guy 
that I am  :-)

-- 
Phillip Windell

The views expressed, are my own and not those of my employer, or Microsoft,
or anyone else associated with me, including my cats.
-----------------------------------------------------

On Dec 20, 2:54=A0pm, Rob <nom...@example.com> wrote:
> karthikbalaguru <karthikbalagur...@gmail.com> wrote:
> > On Dec 19, 10:22=A0pm, "Bob Lin \(MS-MVP\)" <nore...@chicagotech.net>
> > wrote:
> >> IPSec and PPTP are more popular. The PPTP is using for client to serve=
r.
> >> IPSec can be used as cleint to server or site to site VPN. This search
> >> result may help.
>
> > Thx for your response. But it seems that PPTP can support only one
> > tunnel at a
> > time for each user. Therefore, its proposed successor, L2TP (a hybrid
> > of PPTP
> > and another protocol, L2F ) can support multiple, simultaneous tunnels
> > for
> > each user.
>
> > So, shouldn't L2TP be popular ?
>
> I think you should know that "what is popular" is not determined by
> what can do most, what is technically superior and other such reasons
> that you run in to when you do a comparison of VPN technologies as
> a technician.
>
> What is popular is determined by what sells best, or what is part of
> something that already sells best. =A0When it can do the job, it is used.
>

Yes, that is true. Agreed :-)
Thinking on the similar lines, another query popped
up in my mind. In the case of L2TP, Is it mandatory
that in the 'voluntary tunnel mode', the tunnel should
end at the remote client and in the 'compulsory
tunnel mode', the tunnel should end at the ISP ?

Are there no other scenarios with other endpoints ?

Thx in advans,
Karthik Balaguru

On Dec 22, 5:13=A0am, karthikbalaguru <karthikbalagur...@gmail.com>
wrote:
> On Dec 20, 2:54=A0pm, Rob <nom...@example.com> wrote:
>
>
>
>
>
> > karthikbalaguru <karthikbalagur...@gmail.com> wrote:
> > > On Dec 19, 10:22=A0pm, "Bob Lin \(MS-MVP\)" <nore...@chicagotech.net>
> > > wrote:
> > >> IPSec and PPTP are more popular. The PPTP is using for client to ser=
ver.
> > >> IPSec can be used as cleint to server or site to site VPN. This sear=
ch
> > >> result may help.
>
> > > Thx for your response. But it seems that PPTP can support only one
> > > tunnel at a
> > > time for each user. Therefore, its proposed successor, L2TP (a hybrid
> > > of PPTP
> > > and another protocol, L2F ) can support multiple, simultaneous tunnel=
s
> > > for
> > > each user.
>
> > > So, shouldn't L2TP be popular ?
>
> > I think you should know that "what is popular" is not determined by
> > what can do most, what is technically superior and other such reasons
> > that you run in to when you do a comparison of VPN technologies as
> > a technician.
>
> > What is popular is determined by what sells best, or what is part of
> > something that already sells best. =A0When it can do the job, it is use=
d.
>
> Yes, that is true. Agreed :-)
> Thinking on the similar lines, another query popped
> up in my mind. In the case of L2TP, Is it mandatory
> that in the 'voluntary tunnel mode', the tunnel should
> end at the remote client and in the 'compulsory
> tunnel mode', the tunnel should end at the ISP ?
>
> Are there no other scenarios with other endpoints ?
>

The 'Tunneling models' section in the below link
clarifies it.
http://en.wikipedia.org/wiki/Layer_2_Tunneling_Protocol

Lemme know if there are other scenarios apart from
those mentioned in the above link.

Thx,
Karthik Balaguru

> IPSEC is very widely used for infrastructure VPNs and is not
> proprietary.  Cisco interoperates with Checkpoint interoperates with
> Draytek interoperates with OpenVPN ....... Never found a problem in
> dozens of cases.

In which sense do they "interoperate"?

> OpenVPN is proprietary and will not work with a Draytek router. 

In which sense is OpenVPN proprietary?

> If you do not, setting up and maintaining this simply to support a few
> dialup VPN clients is a big ask. Making a few changes to your firewall for
> GRE is pretty minor by comparison.

I went to the trouble of setting up a personal OpenVPN server (and
corresponding clients) specifically because of the endless problems
I had with firewalls when using PPTP (and I don't know about other
people, but I can't make any change to most of the firewalls to which
I'm exposed; and even when I could I still had problems when several
machines within the same NAT subnet tried to use the same VPN).


        Stefan

Meanwhile, at the comp.dcom.sys.cisco Job Justification Hearings, Stefan 
Monnier chose the tried and tested strategy of:

>> IPSEC is very widely used for infrastructure VPNs and is not
>> proprietary.  Cisco interoperates with Checkpoint interoperates with
>> Draytek interoperates with OpenVPN ....... Never found a problem in
>> dozens of cases.
> 
> In which sense do they "interoperate"?

Which 'they' are you referring to?

>> OpenVPN is proprietary and will not work with a Draytek router.
> 
> In which sense is OpenVPN proprietary?

There's only one implementation of the OpenVPN protocol [that I know of - 
recompiling for different platforms and writing pretty front ends don't 
count as reimplementations in my book]. OpenVPN Solutions LLC [the copyright 
holder] are therefore in a position to dictate what the OpenVPN protocol 
consists of, for example, changing the default UDP port. Anyone can take the 
source and extend it in ways that make it incompatible with OpenVPN, at 
which point it's no longer OpenVPN.

-- 
 <http://ale.cx/> (AIM:troffasky) (UnSoEsNpEaTm@ale.cx)
 20:09:39 up 37 days, 4 min,  5 users,  load average: 0.00, 0.02, 0.05
 DIMENSION-CONTROLLING FORT DOH HAS NOW BEEN DEMOLISHED, 
 AND TIME STARTED FLOWING REVERSELY

In message <jwv1vi85jff.fsf-monnier+comp.os.linux.networking@gnu.org>
Stefan Monnier <monnier@iro.umontreal.ca> was claimed to have wrote:

>> OpenVPN is proprietary and will not work with a Draytek router. 
>
>In which sense is OpenVPN proprietary?

In the sense that OpenVPN built their own protocol rather than relying
on one of the existing standards.

There is a lot I like about OpenVPN, but the client side stuff is just
downright nasty to configure, maintain, or even use.  It's great for
techies, but I couldn't imagine putting it in front of an end user.

alexd wrote:
> Meanwhile, at the comp.dcom.sys.cisco Job Justification Hearings, Stefan 
> Monnier chose the tried and tested strategy of:
> 
>>> IPSEC is very widely used for infrastructure VPNs and is not
>>> proprietary.  Cisco interoperates with Checkpoint interoperates with
>>> Draytek interoperates with OpenVPN ....... Never found a problem in
>>> dozens of cases.
>> In which sense do they "interoperate"?
> 
> Which 'they' are you referring to?
> 
>>> OpenVPN is proprietary and will not work with a Draytek router.
>> In which sense is OpenVPN proprietary?
> 
> There's only one implementation of the OpenVPN protocol [that I know of - 
> recompiling for different platforms and writing pretty front ends don't 
> count as reimplementations in my book]. OpenVPN Solutions LLC [the copyright 
> holder] are therefore in a position to dictate what the OpenVPN protocol 
> consists of, for example, changing the default UDP port. Anyone can take the 
> source and extend it in ways that make it incompatible with OpenVPN, at 
> which point it's no longer OpenVPN.
> 

While it is true (AFAIK) that OpenVPN is the only implementation of the 
OpenVPN protocol, the protocol is built on SSL - thus the encryption 
part is very much standard.  The authentication methods are also 
standard - it's only a certain amount of control information that is 
OpenVPN specific, and information on that is easily available as is the 
reference source code (the OpenVPN code).

As OpenVPN source code is under the GPL, it is certainly true that 
anyone can take that code and extend it or change it.  It won't be 
OpenVPN any more (I'm guessing the name is trademarked), and if it is 
incompatible then it will be of pretty limited use.  However, this means 
that if the OpenVPN Technologies (the company behind OpenVPN) ever 
decided to make a new version that is incompatible and closed off, then 
it would be a simple matter to fork the code and release a "FreeVPN" 
that remained open and free.  The only reason that no one has done 
anything like that, or bothered to make other implementations of the 
protocol, is that the official OpenVPN software and support do a 
perfectly good job.

As for your examples of port numbers, OpenVPN has had an IANA official 
port number since 2004.  And if you want to change it, it's just an 
entry in the configuration file.

Dave Warren wrote:
> In message <jwv1vi85jff.fsf-monnier+comp.os.linux.networking@gnu.org>
> Stefan Monnier <monnier@iro.umontreal.ca> was claimed to have wrote:
> 
>>> OpenVPN is proprietary and will not work with a Draytek router. 
>> In which sense is OpenVPN proprietary?
> 
> In the sense that OpenVPN built their own protocol rather than relying
> on one of the existing standards.
> 
> There is a lot I like about OpenVPN, but the client side stuff is just
> downright nasty to configure, maintain, or even use.  It's great for
> techies, but I couldn't imagine putting it in front of an end user.

I would say the same thing about any VPN solution other than OpenVPN. 
For the most part, we have windows clients and linux servers.  When 
someone needs OpenVPN access, I just give them a copy of the windows 
installer, and generate a key and a configuration file (which is simply 
a sample config file with the remote address modified appropriately). 
The setup is vastly easier than other ways to handle VPNs, especially if 
the client is behind a router or needs to connect to multiple VPNs.

In other cases, we've provided routers with OpenWRT installed and the 
client configured.  The user plugs in the router, and has VPN access via 
one of the network ports.  It couldn't be easier.

Stefan Monnier wrote:
>> IPSEC is very widely used for infrastructure VPNs and is not
>> proprietary.  Cisco interoperates with Checkpoint interoperates with
>> Draytek interoperates with OpenVPN ....... Never found a problem in
>> dozens of cases.
> 
> In which sense do they "interoperate"?
> 
>> OpenVPN is proprietary and will not work with a Draytek router. 
> 
> In which sense is OpenVPN proprietary?
> 

I think the poster means that the protocol is not an official standard 
held by an independent body.  That's true, even though it is built 
around existing standards and is freely available.

>> If you do not, setting up and maintaining this simply to support a few
>> dialup VPN clients is a big ask. Making a few changes to your firewall for
>> GRE is pretty minor by comparison.
> 
> I went to the trouble of setting up a personal OpenVPN server (and
> corresponding clients) specifically because of the endless problems
> I had with firewalls when using PPTP (and I don't know about other
> people, but I can't make any change to most of the firewalls to which
> I'm exposed; and even when I could I still had problems when several
> machines within the same NAT subnet tried to use the same VPN).
> 

I have no doubt that OpenVPN is much easier to configure and work with 
both for the server and clients.  Most of the servers I have configured 
have been on small, cheap LinkSys routers using OpenWRT, with multiple 
OpenVPN configurations - an independent OpenVPN network for each network 
port on the device.  Different clients have OpenVPN connections to 
different servers, and can easily connect to or disconnect from the 
networks as they require.  Each server can have multiple clients for the 
different VPN networks as needed.  Each client can be connected to 
multiple servers.  And both the servers and clients are typically behind 
at a NAT router.  This kind of flexibility is simply impossible with 
other VPN solutions.

>>> IPSEC is very widely used for infrastructure VPNs and is not
>>> proprietary.  Cisco interoperates with Checkpoint interoperates with
>>> Draytek interoperates with OpenVPN ....... Never found a problem in
>>> dozens of cases.
>> In which sense do they "interoperate"?
> Which 'they' are you referring to?

Cisco, Checkpoint, Draytek, and OpenVPN.  Or to put the question more
precisely and avoid potential misunderstandings on my part:

  What is meant by "interoperates" in "Cisco interoperates with
  Checkpoint interoperates with Draytek interoperates with OpenVPN"?

In my world, "interoperate" in this context would mean something like "a
client from one company can connect to a server of the other company".
But clearly, that's not what is meant above since only an OpenVPN client
can connect to an OpenVPN server (don't know about the other ones).


        Stefan