PROTECTION OF UNICAST AND MULTICAST TRAFFIC IN WDMMESH NETWORKS:ASURVEY - Computer Science Research and Technology - page 11

Table 1. Ill ustration of protection path for the primary path shown in Figure7
Link on Primary Path
1-2-3-6-4-5

Corresponding
Protection Path

(1,2) 1-3-6-4-5

(3,6) 1-2-3-4-5

(6,4) 1-2-3-4-5

Table 2. Resource allocation for source destination pair (1,4) and (4, 5) of the network in
Figure8

SD
Pair

Primary
Path

Protection Path
(protected link)

Path Protection
Scheme

(1,4) 1-6-3-4 1-2-5-4 (1,6)

1-2-5-4 (6,3)
1-2-5-4 (3,4)
4-3-2-5 (4-5) (4,5) 4-5

Partial Path
Protection
Scheme

(1,4) 1-6-3-4 1-2-3-4 (1,6)

1-6-5-4 (6,3)
1-2-5-4 (3,4)
4-3-2-5 (4,5) (4,5) 4-5

2.2.4. Sub-Path Protection [21]
This scheme has two main steps: (1) a large network is divided into several smaller areas
using the open shortest path first (OSPF) routing algorithm; and then (2) two fiber-disjoint
paths р w and р b are computed for a given connection request d in such a way that р w and р b
enter (or exit) an area from the same ingress (or egress) area border router (ARB) if d is an
inter-area connection, and they remain in the same area if d is an intra-area connection.

Figure 9. An example 18-nodes nationwide network where each cloud denotes an area.

Consider an inter-area connection between node-pair (3,16) as shown in Figure9. The
working path р w is <3,4,7,14,16>, and the backup path р b is <3,6,5,7,11,14,17,16>. The paths
р w and р b exit area 1 (and enter area2) from the same ABR 7 and exit area 2 (and enter area 3)
from the same ABR 14. The ABRs 7 and 14 segment р w and р b into three sub-paths as:
<3,4,7> ( р w 1 ), <7,14> ( р w 2 ), and <14,16> ( р w3 ) for р w ; <3,6,5,7> ( р b 1 ), <7,11,14> ( р b 2 ), and
<14,17,16> ( р b 3 ) for р b [13]. Each ( р wi , р bi ) pair corresponds to the working and backup paths