Forwarding Media Access Control (MAC) Frames over Multiple Access Protocol over Synchronous Optical Network/Synchronous Digital Hierarchy (MAPOS)
RFC 3422

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• 02

Network Working Group                                         O. Okamoto
Request for Comments: 3422                                   M. Maruyama
Category: Informational                                 NTT Laboratories
                                                               T. Sajima
                                                        Sun Microsystems
                                                           November 2002

       Forwarding Media Access Control (MAC) Frames over Multiple
  Access Protocol over Synchronous Optical Network/Synchronous Digital
                           Hierarchy (MAPOS)

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

IESG Note

   This memo documents a way of tunneling Ethernet frames over MAPOS
   networks.  This document is NOT the product of an IETF working group
   nor is it a standards track document.  It has not necessarily
   benefited from the widespread and in-depth community review that
   standards track documents receive.

Abstract

   This memo describes a method for forwarding media access control
   (MAC) frames over Multiple Access Protocol over Synchronous Optical
   Network/Synchronous Digital Hierarchy (MAPOS), thus providing a way
   to unify MAPOS network environment and MAC-based Local Area Network
   (LAN) environment.

1. Network Model

   In the Network model assumed in this memo, MAC-based LAN traffic is
   forwarded by a MAPOS switched network.  This model allows distant
   LANs to be interconnected to form a single LAN segment.  Transparent
   LAN Service (TLS) is provided by encapsulating MAC frames in MAPOS
   frames and by mapping MAC addresses to MAPOS addresses.

Okamoto, et. al.             Informational                      [Page 1]
RFC 3422            Forwarding MAC Frames over MAPOS       November 2002

   This network model is shown in figure 1. "MAPOS network" is composed
   of MAPOS switches, SONET/SDH leased lines and optical fiber cables.
   A LAN is connected to a MAPOS network by a Network Adapter (NA) which
   has a MAPOS interface and an ethernet interface.  A unique MAPOS
   address is assigned to each NA by NSP (Node-Switch Protocol) [2].

                                +-----------+
      MAC-based LAN N1 +---+    |   MAPOS   |    +---+ MAC-based LAN N2
        ---------------|   |----|  network  |----|   |---------------
         |             +---+    |           |    +---+             |
      +-----+         Network   |    N0     |   Network         +-----+
      |     |         adapter   +-----------+   adapter         |     |
      +-----+            B1                       B2            +-----+
      Host H1                                                   Host H2

            Figure 1. VPN network service model with LANs N1 and N2

   Host H1 in LAN N1 and host H2 in LAN N2 are connected to distinct
   MAC-based LANs.  Transparent LAN service is provided by MAPOS network
   N0 exchanging MAC frames between Host H1 and Host H2.

   Using this mechanism, a single VLAN segment can be setup from
   multiple LANs that may be geographically located far away from each
   other.

   The use of a switched technology is recommended for building a MAC-
   based LAN.  In some cases, however, this becomes a requirement.  A
   likely example is the situation where a MAC-based LAN having two
   network adapters, both attached to the same MAPOS network (for
   redundancy).  If the LAN is built using shared (non-switched)
   technology, then this loop configuration is bound to be stormed by
   incessant broadcast traffic.  This can only be circumvented by using
   switched technology with support for broadcast spanning tree [7].

2. Forwarding a MAC Frame

   This section describes the MAC frame forwarding mechanism in the
   MAPOS network.

2.1. Outline

   In figure 2, LANs N1 and N2 communicates via MAPOS network N0.  NAs
   B1 and B2 are gateways into Network N0, and they each have a MAPOS
   interface and an ethernet interface.

Okamoto, et. al.             Informational                      [Page 2]
RFC 3422            Forwarding MAC Frames over MAPOS       November 2002

                                +------------+
                                |MAPOS header|
      +-----------+             +------------+             +-----------+
      | MAC header| encapsulate | MAC  header| decapsulate | MAC header|
      +-----------+ ----------> +------------+ ----------> +-----------+
      |information|             | information|             |information|
      +-----------+             +------------+             +-----------+
        MAC frame             Bridged MAPOS frame             MAC frame

                                +------------+
        LAN N1         +---+    |    MAPOS   |    +---+         LAN N2