Network protection architecture

Details Network protection architecture Network protection architecture

2000-06-08

2003-09-23

Eng, David Y. (Department: 2155)

Electrical computers and digital processing systems: multicomput

Computer-to-computer session/connection establishing

Network resources access controlling

Reexamination Certificate

active

06625653

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to network protection architectures in general, and ring interworking architectures in particular.
BACKGROUND OF THE INVENTION
ITU-T Recommendation G.842 (April 1997) entitled “
Interworking of SDH Network Protection Architectures
” (hereinafter referred to as “G.842” and whose contents are incorporated by reference) discusses dual ring network protection architectures including inter alia a form of dual node interconnection termed ring interworking. One implementation of ring interworking is the so-called SubNetwork Connection Protection (SNCP) ring interworking architecture which is characterized by its top ring and its bottom ring being mirror images of one another.
Generally speaking, the term ring interworking refers to a dual ring network topology which includes top and bottom rings each having an I/O node with a transmit tributary and a receive tributary, two west working channels between the I/O node and an west interconnection node from the perspective of the top ring, and two east protection channels between the I/O node and an east interconnection node from the perspective of the top ring. The terms “working channel” and “protection channel” are purely descriptive to distinguish between two identical channels except that a ring's working channel is typically its default active channel in terms of signal flow therealong. Only one of a ring's working and protection channels may be active in terms of end-to-end signal flow therealong at any one time, if at all.
The opposite west interconnection nodes of the top and bottom rings define a west interconnection interface and, similarly, the opposite east interconnection nodes of the top and bottom rings define an east interconnection interface. Each interconnection interface has a pair of lines bridging across the rings, one of which is employed as a so-called top down receive line from the transmit tributary of the top ring's I/O node to the receive tributary of the bottom ring's I/O node via either a top down west working channel or a bottom up east protection channel. Conversely, the other line is employed as a so-called bottom up transmit line from the transmit tributary of the bottom ring's I/O node to the receive tributary of the top ring's I/O node via either a bottom up west working channel or a bottom up east working channel.
It is a commonly purported that ring interworking and, in particular, a G.842 compliant SNCP ring interworking architecture provides top down fiber optic network survivability as long as one of the top ring's top down working or protection channels, one of the bottom ring's top down working or protection channels, and one of the east or west interconnection interfaces' receive lines remain intact. However, topological analysis of a G.842 compliant SNCP ring interworking architecture reveals that the east and west interconnection interfaces' receive lines are each connectable to the receive tributary at the bottom ring's I/O node from their respective sides only from the perspective of the top ring, namely, the west interconnection interface's receive line is only connectable to the bottom ring's I/O node from the west and conversely the east interconnection interface's receive line is only connectable to the bottom ring's I/O node from the east. Due to this, a G.842 compliant SNCP ring interworking architecture cannot provide top down fiber optic integrity in the case of a double fiber optic failure involving the west interconnection interface's receive line and the bottom ring's east protection channel nor the east interconnection interface's receive line and the bottom ring's west working channel.
The above analysis equally applies to bottom up fiber optic network survivability by virtue of the symmetrical nature of a G.842 compliant SNCP ring interworking architecture.
There is a need to provide a network protection architecture with fiber optic network survivability capabilities above and beyond those of a G.842 compliant SNCP ring interworking architecture.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a network protection architecture comprising:
(a) a top ring with an I/O Node A having a transmit tributary TT
A
and a receive tributary RT
A
, a top down west working channel WC
AB
, a bottom up west working channel WC
BA
, a top down east protection channel PC
AC
, a bottom up east protection channel PC
CA
, and two double switch interconnection nodes B and C;
(b) a bottom ring with an I/O Node Z having a transmit tributary TT
Z
and a receive tributary RT
Z
, a top down west working channel WC
DZ
, a bottom up west working channel WC
ZD
, a top down east protection channel PC
EZ
, a bottom up east protection channel PC
ZE
, and two double switch interconnection nodes D and E;
(c) said interconnection nodes B and D having a receive line RL
BD
and a transmit line TL
DB
bridging thereacross;
(d) said interconnection nodes C and E having a receive line RL
CE
and a transmit line TL
EC
bridging thereacross;
(e) said interconnection node B having switches S
1
and S
5
, said switch S
1
switching said receive line RL
BD
between said working channel WC
AB
between and said protection channel PC
AC
, and said switch S
5
switching said working channel WC
BA
between said transmit line TL
DB
and said transmit line TL
EC
;
(f) said interconnection node C having switches S
2
and S
6
, said switch S
2
switching said receive line RL
CE
between said working channel WC
AB
and said protection channel PC
AC
, and said switch S
6
switching said protection channel PC
CA
between said transmit line TL
DB
and said transmit line TL
EC
;
(g) said interconnection node D having switches S
3
and S
7
, said switch S
3
switching said transmit line TL
DB
between said working channel WC
ZD
and said protection channel PC
ZE
, and said switch S
7
switching said working channel WC
DZ
between said receive line RL
BD
and said receive line RL
CE
; and
(h) said interconnection node E having switches S
4
and S
8
, said switch S
4
switching said transmit line TL
EC
between said working channel WC
ZD
and said protection channel PC
ZE
, and said switch S
8
switching said protection channel PC
EZ
, between said receive line RL
BD
and said receive line RL
CE
.
The network protection architecture of the present invention is based on the realization that a G.842 compliant SNCP ring interworking architecture with additional limited switching capability can provide full top down and bottom up fiber optic network survivability in the face of all fiber optic failures except truly catastrophic failures.


REFERENCES:
patent: 5687318 (1997-11-01), Oksanen et al.
patent: 6014708 (2000-01-01), Klish
patent: 6070188 (2000-05-01), Grant et al.
patent: 6442694 (2002-08-01), Gergman et al.
patent: 6452934 (2002-09-01), Nakata
ITU-T Recommendation G.842 (04/97), Interworking of SDH Network Protection Architectures, pp 32.

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