RFC 3077 (rfc3077) - Page 2 of 25

A Link-Layer Tunneling Mechanism for Unidirectional Links

RFC 3077            LL Tunneling Mechanism for UDLs           March 2001


   that supports multiple feeds and receivers.  Note, this mechanism is
   not designed for topologies where a pair of nodes are connected by 2
   unidirectional links in opposite direction.

   The tunneling mechanism requires that all nodes have an additional
   interface to an IP interconnected infrastructure.

   The tunneling mechanism is implemented at the link-layer of the
   interface of every node connected to the unidirectional link.  The
   aim is to hide from higher layers, i.e., the network layer and above,
   the unidirectional nature of the link.  The tunneling mechanism also
   includes an automatic tunnel configuration protocol that allows nodes
   to come up/down at any time.

   Generic Routing Encapsulation [RFC 2784] is suggested as the tunneling
   mechanism as it provides a means for carrying IP, ARP datagrams, and
   any other layer-3 protocol between nodes.

   The tunneling mechanism described in this document was discussed and
   agreed upon by the UDLR working group.

   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
   document, are to be interpreted as described in [RFC 2119].

2. Terminology

   Unidirectional link (UDL): A one way transmission link, e.g., a
      broadcast satellite link.

   Receiver: A router or a host that has receive-only connectivity to a
      UDL.

   Send-only feed: A router that has send-only connectivity to a UDL.

   Receive capable feed: A router that has send-and-receive connectivity
      to a UDL.

   Feed: A send-only or a receive capable feed.

   Node: A receiver or a feed.

   Bidirectional interface: a typical communication interface that can
      send or receive packets, such as an Ethernet card, a modem, etc.







Duros, et al.               Standards Track