Difference between ISDN,Frame Relay,Site to SIte VPN, PPP,HDLC

jskfan
jskfan used Ask the Experts™
on
I need some to clear up the confusion between the connection stated in the Title above.
If I understand a little bit :
Site to Site VPN,PPP,HDLC can connect through DSL to internet and communicate with other side.
for the Frame Relay, the FR provider connects you through FR switch on his side , and you will use specific hardware to connect you serial interface to the FR switch.

ISDN has a port that looks like RJ45 but larger, I am not sure where it will connect to, and if the provider will give you DLCI/PVC/CRI just like FR.

THANKS
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Don JohnstonInstructor
Top Expert 2015

Commented:
VPN has nothing to do with any of this. You can create a VPN tunnel over any layer1 or 2 connection.

F/R doesn't require any special hardware on the customer side.

ISDN is basically a circuit switched (dial-up) point-to-point service.
Frame Relay is usually provided over a point to point "serial" circuit, terminated on teh providers router and with a handover on Ethernet, it can be provided to use a customer router.

ISDN is the digital equivalent of a an analogue phone circuit, it has two main forms, a 2 channel and eithera 30 or 24 channel depending on if it is American or European, there are then multiple signalling types, the most common being Q931. It can be used for Voice witha suitable phone or phone system, for data with a suitable terminal adaptor or router, or for "analogue data with a suitable terminal adaptor such as a Dialogic Diva Server.

VPN is encapsulating traffic to secure it across an untrusted network.

These are three completely different technologies.

Instead of using a Frame Relay provider, many companies have migrated to using VPN connections over the internet.

Instead of ISDN for voice many companies are moving to VoIP, sometimes they might use Franme Relay or a VPN to connect remote sites for VoIP.

Author

Commented:
I was asking about physical connection , end to end.
for instance , Site to Site VPN, you need to plug the Cisco router external interface to DSL modem and configure  the Tunnel. This is done on both ends.
I am not sure about:
 ISDN,Frame Relay, PPP,HDLC, how physicall they get connected end to end
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Don JohnstonInstructor
Top Expert 2015
Commented:
I was asking about physical connection , end to end.
for instance , Site to Site VPN, you need to plug the Cisco router external interface to DSL modem and configure  the Tunnel. This is done on both ends.

Except for dark fiber, physical connections are never end-to-end. They simply connect you to a piece of provider equipment.

Author

Commented:
I meant , for instance site to site vpn:
you plug the cisco router external interface to DSL modem RJ45 in one side and do the same in the other side. and all there is between 2 sites is the Internet cloud.
How do you connect 2 or more sites in order to use HDLC,ISDN.PPP,Frame Relay.?
are there any specific interface on the routers.?
Don JohnstonInstructor
Top Expert 2015
Commented:
How do you connect 2 or more sites in order to use HDLC,ISDN.PPP,Frame Relay.?

If you're using DSL, then the provider probably requires PPP. HDLC or Frame-Relay isn't an option. The layer 2 protocol that you use is determined by the service that your provider specifies.

For example, you may have DSL and run PPP on top of that. But I've got cable. So I'm running ethernet at layer 2. I simply can't run PPP, HDLC or Frame-Relay. I have to use ethernet.

But VPN's are based on layer 3. So as long as we're both running IPv4, we're fine.

Now, if you really want to run HDLC, you'll need to obtain a layer 1 point-to-point service such as a T1, fractional T1 or T3 service. Then you can run HDLC or PPP.  ISDN is basically a dial-up fractional T1 (or a full T1 if you get PRI service). Which means if you've got ISDN between your sites, you can use HDLC or PPP.
Gajendra RathodLead System Administrator
Commented:
HDLC, ISDN, Frame Relay and PPP are technologies used when you have lease line between to site. The lease line is costly but secure.

HDLC, Frame Relay and PPP are layer1 and layer 2 protocols for connection between two sites. Special modems are required for this type communication. These modems are connected to router via smart serial port.

ISDN is connected to one device name NT1 box. This NT1 box has input for ISDN link (it look like normal telephone line) and output is connected to ISDN interface of router.      

VPN is basically used to provide connectivity between two sites or machines that are directly connected to internet.
Instructor
Top Expert 2015
Commented:
HDLC, Frame Relay and PPP are layer1 and layer 2 protocols for connection between two sites. Special modems are required for this type communication. These modems are connected to router via smart serial port.

HDLC, Frame-Relay and PPP are layer 2 protcols. The can be used over any point-to-point link. Analog dial-up, ISDN, DS0, DS1 or DS3.

Author

Commented:
Thanks

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