Cisco HDLC and PPP

I wonder Nowadays where HDLC and PPP are used.
Most of companies use MPLS ,MDVPN, Client/Server IPSEC VPN.

I know that HDLC and PPP are WAN protocols, but I  am not sure when to use them nowadays.

Any help will be  very much appreciated.

Thanks
jskfanAsked:
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skullnobrainsCommented:
I thought there is no longer a modem between company external routers and the ISP, nowadays.
HDLC and PPP if I understand is used for the traffic going through modems,ISDN...

yes : wherever there is a dedicated line and no need for fancy security, PPP is quite sufficient.

it is still the default for modem and xdsl connections, for example.

more complex protocols are required when you want to be able to route in both directions or when you need additional encryption. in some cases this is achieved by running a secure connection over PPP.

note : usage of IPSEC VPNs in cases where you don't need to route in both ways is very common but suboptimal in terms of both performance and security
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Hassan BesherCommented:
Still used in the core also Serial Link are used for Communicating with Legacy WAN links of Telco and nowdays Modified for of Ethernet called Metero Ethernet which help for Terminating WAN link in Ethernet and there is no need of complex protocols as Framerealy and PPP if we use Ethernet.
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Don JohnstonInstructorCommented:
While not as common as they were 10-20 years ago, there are still tons of T-1 and T-3 point to point circuits.  If you've got one connecting your offices, then HDLC or PPP is what you're using.
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jskfanAuthor Commented:
I thought there is no longer a modem between company external routers and the ISP, nowadays.
HDLC and PPP if I understand is used for the traffic going through modems,ISDN...
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Don JohnstonInstructorCommented:
No. Modems are layer 1 devices and have no relation to the layer 2 (or higher) protocol.

If you are connecting to your ISP using a T-1, fractional T-3 or full T-3, you will most likely be using PPP or HDLC.
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jskfanAuthor Commented:
<<<If you are connecting to your ISP using a T-1, fractional T-3 or full T-3, you will most likely be using PPP or HDLC.>>>

I believe most of the companies ,that 's how they connect to their ISPs using(T1,T3,etc..)..
in this case, are they all using PPP or HDLC…OR there are other technologies to connect to ISP without using T1 , T3 ?
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Don JohnstonInstructorCommented:
Cable providers carry their internet over fiber or coax with Ethernet.  There are also providers that offer long-haul Ethernet over fiber.  These technologies are rapidly replacing T-1 and T-3 circuits for internet access as they offer speeds greater than 45mbp/s.

But point to point circuits are still widely used for private connections between company locations.
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jskfanAuthor Commented:
Thank you Guys!
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