Browse Prior Art Database

Isochronous Fiber Distributed Data Interface

IP.com Disclosure Number: IPCOM000105812D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20

Publishing Venue

IBM

Related People

Basso, C: AUTHOR [+4]

Abstract

The Iso LAN basic idea is to provide a dedicated isochronous point-to- point bandwidth between the workstation and the hub concentrator. For FDDI, Fiber Distributed Data Interface, the FDDI-2 Standard defines an isochronous bandwidth capability beside the FDDI-1 local area network protocol, but this isochronous bandwidth is carried by the shared media (on the ring) only, and cannot be exchanged in point-to-point between the workstation and the hub concentrator. The purpose of this proposal is to add this point-to-point capability in order to place FDDI inside the Iso LAN family.

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Isochronous Fiber Distributed Data Interface

      The Iso LAN basic idea is to provide a dedicated isochronous
point-to- point bandwidth between the workstation and the hub
concentrator.  For FDDI, Fiber Distributed Data Interface, the FDDI-2
Standard defines an isochronous bandwidth capability beside the
FDDI-1 local area network protocol, but this isochronous bandwidth is
carried by the shared media (on the ring) only, and cannot be
exchanged in point-to-point between the workstation and the hub
concentrator.  The purpose of this proposal is to add this
point-to-point capability in order to place FDDI inside the Iso LAN
family.

      The Isochronous FDDI (IsoFDDI) interface is an integrated
Voice/Video/Data interface that provides traditional FDDI packet
service and isochronous digital channels on a full duplex interface
to the desktop over the existing wiring (STP, UTP, Fiber).

      The medium between the workstation and the hub is shared for
the packet channel (standard FDDI protocol) but dedicated for the
isochronous channels.

      The interface consists of a multiplexed  bit stream of digital
data of various channel types over which a variety of services can be
of fered.  The channel types are:

      P-Channel: This is the traditional packet channel (<= 100 Mbps)
running the FDDI MAC protocol.

      D-Channel: A 64 kbps full duplex packet channel for the
provision of Network Access Signalling via the Q.930 protocol family.

      B-Channel: A full duplex 64 kbps isochronous channel.

      C-Channel: A full duplex isochronous channel whose bandwidth is
a multiple of 64 kbps (N x B channels).

      The D and B Channels are ISDN compatible.

      The IsoFDDI proposal provides for a TDM frame which results
from the time-division multiplex of the contents of the P, D, B, and
C channels along with synchronization and control information.
FDDI-1 frames are carried on the P-Channel.

      The following factors motivated the design of the IsoFDDI:

1.  A variable Iso bandwidth (up to 98.304 Mbps) defined in the 100
    Mbps bandwidth of the link.

2.  IsoFDDI takes advantage of point-to-point connections between
    stations and hub.  Since the logical FDDI "Ring" is actually
    imple mented under a physical star topology when stations are
    attached to a wiring hub, the isochronous traffic can be handled
    in the star structure of the wiring hub, allowing each station to
    access the full isochronous bandwidth.

3.  The IsoFDDI link can support FDDI-1 stations with minimal
    hardware changes.  In this case, these 'IsoFDDI-friendly'
    stations just ignore the isochronous bandwidth appearing on the
    link.

4.  The IsoFDDI does not add particular requirements on the
    transmission media.

5.  Low-level multiplex of traffics is used to minimize the impact of
    IsoFDDI on FDDI-1.  This allows to permanently keep the IsoFDDI
    link...