RFC 2363 (rfc2363) - Page 3 of 12

PPP Over FUNI

RFC 2363                     PPP Over FUNI                     July 1998


4. Multi-Protocol Encapsulation

   This specification uses the principles, terminology, and frame
   structure described in "Multiprotocol Encapsulation over ATM
   Adaptation Layer 5" [4].

   The purpose of this specification is not to document what is already
   standardized in [4], but to specify how the mechanisms described in
   [4] are to be used to map PPP onto a FUNI-based  ATM network.
   Section 1 within [4] defines the two mechanisms for identifying the
   Protocol Data Unit (PDU) payload field's protocol type: virtual
   circuit based multiplexing, and Logical Link Control (LLC)
   encapsulation.  In the former technique, the payload's protocol type
   is implicitly agreed to by the end points for each virtual circuit
   using provisioning or control plane procedures.  When using the LLC
   encapsulation technique, the payload's protocol type is explicitly
   identified on a per PDU basis by an in-band LLC header, followed by
   the payload data.

   When transporting a PPP payload over FUNI, an implementation:

        1. MUST support virtual circuit multiplexed PPP payloads as
        described in section 5 below by mutual configuration or
        negotiation of both end points.  This technique is referred to
        as "VC-multiplexed PPP".

        2. MUST support LLC encapsulated PPP payloads on PVCs as
        described in section 6 below by mutual configuration or
        negotiation of both end points.  This technique is referred to
        as "LLC encapsulated PPP".

        3. For SVC set up, an implementation MUST negotiate using the
        Q.2931 [9] Annex C procedure, encoding the Broadband Lower Layer
        Interface (B-LLI) information element to signal either VC-
        multiplexed PPP or LLC encapsulated PPP.  The details of this
        control plane procedure are described in section 7.

If an implementation is connecting through a Frame Relay/ATM FRF.8 [7]
        service inter-working unit to an RFC 1973 [6] end point, then it
        MUST use LLC encapsulated PPP payloads.  Frame Relay/ATM FRF.8
        inter-working units are exempted from the requirement to support
        VC-multiplexed PPP.  This exemption allows the FR/ATM IWU to
        remain compliant with FRF.8 when the PPP over FUNI end point is
        inter-operating with an RFC 1973 end point.

5. Virtual Circuit Multiplexed PPP Over FUNI

        The FUNI protocol data unit (PDU) format [2] is as follows:



Gross, et. al.              Standards Track