HDLC vs. PPP regarding support of mulitple network layer protocols

johnifanx98

I learned each vendor has its own specific proprietary header to accommodate multiple network protocol layers, thus HDLC is vendor specific and not compatible.

PPP can resolve this issue.

I don't know why it requires a proprietary header in HDLC to support multiple network layer protocols.

But I'm just guessing the reason PPP can resolve this issue is that PPP has a NCP layer, am I right?

NetworkVeteran

johnifanx98 wrote: »

I learned each vendor has its own specific proprietary header to accommodate multiple network protocol layers, thus HDLC is vendor specific and not compatible.

I wouldn't entirely agree with that characterization. While cHDLC is Cisco's non-standard extension to the HDLC protocol, most networking vendors simply support the cHDLC protocol.

I don't know why it requires a proprietary header in HDLC to support multiple network layer protocols.

I will turn that around on you! Try listing all the standard HDLC header fields--Google if you need to--and tell me which one you would use to identify an upper-layer protocol.

johnifanx98

NetworkVeteran wrote: »

I wouldn't entirely agree with that characterization. While cHDLC is Cisco's non-standard extension to the HDLC protocol, most networking vendors simply support the cHDLC protocol.


I will turn that around on you! Try listing all the standard HDLC header fields--Google if you need to--and tell me which one you would use to identify an upper-layer protocol.

I know standard HDLC frame does not have a field to specify the network laye protocol name. But is it hard to make that number vendor independent?

NetworkVeteran

johnifanx98 wrote: »

But is it hard to make that number vendor independent?

There's just no driving business need to spend the money to do so, since most vendors have already implemented the Cisco HDLC solution, and interoperate just fine.