1. Introduction

   This transparent cell transport service allows migration of ATM
   services to a PSN without having to provision the ATM subscriber or
   customer edge (CE) devices.  The ATM CEs will view the ATM
   transparent cell transport service as if they were directly connected
   via a Time Division Multiplexer (TDM) leased line.  This service is
   most likely to be used as an internal function in an ATM service
   provider's network as a way to connect existing ATM switches via a
   higher-speed PSN, or to provide ATM "backhaul" services for remote
   access to existing ATM networks.

1.1. Specification of Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [1].