++Unidirectional VS. Bidirectional

[zsq...@my-deja.com]

All,

Can someone please elaborate on the difference between uni and bi
directional linear switching as it releates to 2 NEs connected together?
Also, how does this relate to aps using the K1 and K2? Where does the
K1 and K2 flow? on protection or working channel?

In a unidirectional, does it mean that there is only a TX fiber from
NE1 to an RX fiber on NE2?

NE1--TX/working-->>>----RX--NE2
\tx/protect-->>>--rx/

I am led believe that this is unidirectional, b/c traffic doesn't go
back the other 'bidirectional' way. So...does this also mean that Ne2
doesn't have traffic flowing back to NE1?

In a bidirectional does it mean that there is a working tx and rx pair
and also a protect tx and rx pair? And how/where does the K1 and K2
flow?

NE1----tx/working-->>---RX--NE2
----rx/working--<<---TX--
----tx/protect>>-----rx
----rx/protect<<-----tx

The questions may be several, please inquire if you need for me to
elaborate futher.

Any insights are helpful for me (+ all of us who are also learning)

Thanks!

Sent via Deja.com http://www.deja.com/
Before you buy.

[Danny Levy]

Always there are two fibers, one for tx and one for rx between NEs.
In case of additional protection fiber the picture is

NE1----tx/working-->>---RX--NE2
----rx/working--<<---TX--
----tx/protect>>-----rx
----rx/protect<<-----tx

Uni directional - If one fiber fails - only this fiber will be moving to the protection fiber.
i.e. if tx/working will fail the two active fibers will be tx/protect and rx/working.

Bi directional - both rx and tx will move to the protection fiber.
i.e. if tx/working will fail the two active fibers will be tx/protect and rx/protect.

See G.783 for K1/K2 flow.
Danny.

[Hari TS]

Your questions are case dependent

1+1 UNI
In this case it is not necessary that you have both fibers hooked up.
you just need Tx to Rx connection. If the Rx see a failure it will
switch to the protection fiber immediately. This is because, 1+1 UNI
does not use the K bytes for handshaking.

1:N UNI,1+1 BI and 1:N BI
You need both direction fibers because K bytes handshaking is a must.

The K bytes are always transmitted on the protection fiber. The receiver
is supposed to ignore the K bytes received on the working except for
AIS-L (MS-AIS) alarm.

The concept of UNI and BI comes from the fact that if a unidirectional
failure occurs on a working channel, UNI will cause the failed direction
of the working channel only to switch. This means only node B will do
the switch in the following case of 1+1 aps. Whereas in BI, the node A
will also do a switch when it receive SF/1 (Signal failre for channel 1)
code in the received K1 byte.
The actual K byte handshake you can read from a previous answer i wrote
against the subject "another Q for k1 and k2 byte" in the month of
august.

|-------|---| fault |---|---------|
| _____|tx |-----------------X---------------->|rx |-->\ |
| |bri |(w)| |(W)| \ |
| |dge |rx |<----------------------------------|tx | \-- |
|--| |---| RR/1---> |---|switch |
| |----|tx |---------------------------------->|rx |---> |
| |(p)| |(p)| |
| |rx |<----------------------------------|tx | |
--------|---| <--Sf/1 |---|----------
Node A Node B

Hari