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Handling Local Administered Media Access Control Addresses in LAN Interconnect

IP.com Disclosure Number: IPCOM000104353D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 155K

Publishing Venue

IBM

Related People

Derby, J: AUTHOR [+5]

Abstract

When LANs are interconnected across a wide area transport network, all LAN station Media Access Control (MAC) addresses in the interconnected LANs must be unique. If a LAN station uses a globally administered MAC address, this address is guaranteed to be unique. On the other hand, if a LAN station uses a locally administered MAC address, the network administrator must make sure that LAN station addresses are unique within a communicating domain. In other words, if a source station uses an individually locally administered MAC address, then that address must be unique on the LAN to which the destination station is attached. This requirement causes a heavy burden on the network administrators. It is an even bigger problem when interconnecting two LANs from different administrative domains.

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This is the abbreviated version, containing approximately 52% of the total text.

Handling Local Administered Media Access Control Addresses in LAN Interconnect

      When LANs are interconnected across a wide area transport
network, all LAN station Media Access Control (MAC) addresses in the
interconnected LANs must be unique.  If a LAN station uses a globally
administered MAC address, this address is guaranteed to be unique.
On the other hand, if a LAN station uses a locally administered MAC
address, the network administrator must make sure that LAN station
addresses are unique within a communicating domain.  In other words,
if a source station uses an individually locally administered MAC
address, then that address must be unique on the LAN to which the
destination station is attached.  This requirement causes a heavy
burden on the network administrators.  It is an even bigger problem
when interconnecting two LANs from different administrative domains.

      This article describes an efficient mechanism to interconnect
LANs with locally administered MAC addresses across a wide area
transport network without network-wide administration of these
addresses.

      Below some terms are defined to help explain concepts in this
article.

      MAC Address: A MAC address may be either 16 bits or 48 bits.
This address is defined by the IEEE 802 standards.  The 48 bits
address formats for source MAC address and destination MAC address
are shown in Figs. 1 and 2, respectively.  The second bit (UL bit) is
set to zero to indicate a universally administered MAC address.  It
is set to one to indicate a locally administered MAC address.

      Access Agents:  Provide standard interfaces or points of
attachment where protocol-specific local network traffic enters the
Wide Area Network (WAN) backbone.  Components of an access agent
include a protocol agent which knows particular protocols such as
those employed on LANs.  The access agents discussed in this document
are interfacing to external LANs, and are hence also referred to as
LAN Access Agents.

      A MAC address can be an individual address or a group address.
An individual address belongs to one LAN attachment, whereas a group
address can be shared by multiple LAN attachments.  An individual MAC
address of a LAN station may be either globally or locally
administered.  Every physical LAN attachment has a unique MAC address
that is "burned in"; these addresses are globally administered by the
IEEE and so are universally unique.  A LAN attachment may also have a
locally administered MAC address loaded into it.  The locally
administered addresses must be administered in such a way that they
are unique within a communicating domain.  To avoid network-wide
administration of all locally administered MAC addresses, we have
developed a procedure which ensures that locally administered MAC
addresses are unique within a communicating domain.

      A procedure is defined for processing a MAC frame that contains
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