David,
I am sorry if I do not answer your question but it is not clear what you are actually asking about.
The HDLC is a Layer2 protocol, i.e. a protocol defining the communication of adjacent devices directly connected some common medium. Especially in the case of Cisco HDLC, the medium is a point-to-point serial link. The HDLC itself is capable of carrying any Layer3 protocol, including IP, IPX, IPv6, MPLS, AppleTalk, X.25 and so on.
The HDLC is not a direct part of the TCP/IP model. The TCP/IP is actually not concerned with the physical and link layer technologies. It defines the operation of IP, ICMP, ARP, TCP, UDP and some other transport layer protocols, but it does not define how shall the network access layer work in detail. Thus, the TCP/IP is actually quite oblivious to the framing used, be it HDLC, PPP, Ethernet, WiFi, Token Ring, FDDI or any other technology.
that mean that the TCP\IP model not work with IPX OR APPLE TALK MODEL??
IP, IPX and AppleTalk are all Layer3 protocols, and as such, they provide similar functions and are in fact concurring, not cooperating. So, yes, precisely speaking, the TCP/IP model has nothing to do with IPX or AppleTalk.
Please feel free to ask further!
Best regards,
Peter
