Browse Prior Art Database

Shared-Medium-Based Subscriber Ring Access to ATM Networks

IP.com Disclosure Number: IPCOM000112179D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 165K

Publishing Venue

IBM

Related People

Denzel, W: AUTHOR [+4]

Abstract

Described is an architecture that enables a limited number of workstations (WS) to connect via a shared subscriber line to a Network Node (NN) of a packet-switched communication network. Primary goal is to design this optional shared access capability (the conventional point-to-point connection of a single WS to a NN will still be possible) with a minimum amount of both hardware and software.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 37% of the total text.

Shared-Medium-Based Subscriber Ring Access to ATM Networks

      Described is an architecture that enables a limited number of
workstations (WS) to connect via a shared subscriber line to a
Network Node (NN) of a packet-switched communication network.
Primary goal is to design this optional shared access capability (the
conventional point-to-point connection of a single WS to a NN will
still be possible) with a minimum amount of both hardware and
software.

      Fig. 1 shows topological aspects of the environment, whereas
Fig. 2 shows a magnification of one of the WS in Fig. 1.  Assumed is
that a WS has a communication adapter that allows to connect the WS
in a point-to-point manner to a NN of a general packet-switched
network.  The WSs are extended (or more precisely, the communication
adapters in the WS) and T-plugs are used for the cabling system in
order to converge from the conventional point-to-point attachment of
a single WS to a ring-based shared-medium access for multiple WSs.
The primary task of the adapter extension is to determine whether a
packet coming from the upstream link segment is destined for the
present WS (in which case the packet must be received by the present
communication adapter), or for a WS downstream (in which case the
packet must be forwarded to the downstream ring segment).  In
addition, it must be ensured that packets being transmitted by the
present WS are properly inserted into the downstream traffic stream.
These tasks can be achieved with the following hardware components:

o   a packet filter,

o   FIFO buffers (one for each traffic priority supported),

o   a power-off bypass relay (not shown), and

o   marginal glue control logic (not shown).

      Filtering is based on a WS address or connection identifier
contained in the packet header.  Without restricting generality it is
assumed that such a connection identifier is generated in the
negotiations between control instances in the communication adapter
and the NN during connection setup or is known in advance.  If a
packet is destined for the present WS, the packet must be received by
the present communication adapter.  If the packet is destined for
another WS or the NN, the filter has to bypass the packet into the
buffer that corresponds with the packet's priority level.  All bypass
buffers lead to the next downstream WS.  In case of multipoint or
broadcast connections, the filter must both receive and bypass a
packet.  Finally, the filter may discard packets with a corrupted
packet header.

      The filter can be efficiently implemented in a small RAM device
if the connection ID (or WS address) is of moderate size.  For
example, with an 8 bit connection ID one can differentiate between
256 different connections distributed over all WS attached to the
ring.  The connection ID is simply applied as address to the RAM and
the contents determines the appropriate filter function.  Three bits
are sufficient to code the ei...