1+! &1:1 Link protection in SDH (APS)

Unanswered Question
Dec 27th, 2008

Can any one tell me in details what is the difference in 1+1 & 1:1 link protection in SDH (APS switching).

also kindly provide the links for relevant data sheets!!

I have this problem too.
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Tom Randstrom Sat, 12/27/2008 - 11:02

A good reference book with an explanation is from Cisco press "Optical Network Design and Implementation" with a link to the protection definitions and examples provided below:


The 15454 offers these protection options with every software load. The availability of each type of protection option is dependent on the interface type (electrical or optical). The user manuals should spell out the supported protection options.

viyuan700 Sat, 12/27/2008 - 12:35

Can any one tell me in details what is the difference in 1+1 & 1:1 link protection in SDH (APS switching)

There are 2 kind of protection

1. Card protection

1:1 & 1:N protection is available for electrical cards. 1+1 protection dont make sense for these cards as they have to go over optical cards where u have 1+1 protection

link for E1 card protection, have 1:3 (means there is one protection card for 3 working card)protection. look in technical spec


link for STM1 Electrical STM 1 potection here 1:1 protectiion. At high speed doesnot make sense for 1:N kind of protection like E1 card.


1+1 for Optical cards (Its like link protection)

Optical cards offer UPSR/SNCP ,APS/MSP (1+1 unidirectional or bidirectional)


2. Link Protection

Have not seen 1:1 protection for link, its basically like 1+1 but need siganlling for switching whereas in 1+1 if No or degraded siganl it just switches to other path.

Depends on topology can be linear and Ring (UPSR-SONET/SNCP-SDH and BLSR/MS Spring).

you can read chapter 7 for card protection and 12 for link protection(topology)



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