Chapter 2. Technical description 35
2.3 Point-to-point network configuration
The 32 optical channel wavelengths in the IBM 2029 network are divided into
eight shelf bands of four channels, all of which are transmitted over a single fiber
pair and each of which can be managed separately. In the point-to-point
configuration, shelves in the remote site have a one-to-one correspondence with
shelves in the hub site, according to their allocated shelf band pairs.
An IBM 2029 point-to-point network consists of a minimum of two IBM 2029
shelves (a hub shelf and a remote shelf) connected via two fiber pairs. The pair of
shelves are allocated to the same band wavelength (Band 1 through Band 8).
The shelf band wavelengths can be arbitrary, but must be unique within the
Figure 29 on page 36 shows a point-to-point network with four shelves in each
site. These are interconnected using single-mode fiber-optic jumper cables (also
known as pigtails), which connect the OMX West modules in a site to each other,
and the OMX East modules in a site to each other.
The two fiber pairs running between the hub site and the remote site are
connected to an OMX module in the first and last shelves in each site. The first
fiber pair (transmit and receive) connects the OMX East module in the Band 1
hub shelf with the OMX West module in the Band 4 remote shelf. The second
fiber pair (transmit and receive) connects the OMX West module in the Band 4
hub shelf with the OMX East module in the Band 1 remote shelf.
Note that the sequence in which the shelves are interconnected in each site is
balanced so that a given high availability channel of a shelf pair passes through
the same number of OMX modules in either direction through the network. See
2.5, “Protection schemes” on page 39 for more information on high availability
The network traffic flow for Figure 29 on page 36 (using ADF, shown in Figure 22
on page 30), is as follows:
We called all signals originating or destined for the East side of all shelves in the
hub site E-Bx, and for the West side W-Bx (x being the respective band number).
1. Starting from the Band 1 East side at the hub site, the E-B1 signal gets added.
All signals (E-B1, B2, B3, B4) are then sent out (OTS OUT) to the remote site.
2. At the remote site the signals are received on the West side of Band 4 through
OTS IN. At Band 4, the E-B4 signal gets dropped and all other signals (E-B1,
B2, B3) are passed (THRU OUT) to Band 3 West side.
3. Band 3 receives the signals through OTS IN, the E-B3 signal gets dropped
and all other signals (E-B1, B2) are passed (THRU OUT) to Band 2 West side.
4. Band 2 receives the signals through OTS IN, the E-B2 signal gets dropped
and the E-B1 signal is passed (THRU OUT) to Band 1 West side.
5. Band 1 receives the signal through OTS IN, and the E-B1 signal gets dropped.
In the opposite direction:
1. Starting from the West side of Band 1 in the remote site, an E-B1 signal gets
added, then sent out (OTS OUT) to Band 2 West side.