switching devices and makes it easier to gradually add
switches and network devices for expansion based on
business needs, saving on the initial investment costs.
DEALING WITH THE CABLING CHALLENGES
OF A SPINE-AND-LEAF 2-LEVEL
ARCHITECTURE
Data center managers encounter new issues when
deploying a data center with a spine-and-leaf 2-level
architecture. Since a leaf switch is required to connect
each spine switch, managing a massive quantity
of cabling becomes a major challenge. A mesh
interconnection module (Table 1) can solve this
difficult problem.
Many users have upgraded to high-density 40 Gb/s
switch line cards to break out as part of 10 Gb/s
applications. In fact, according to the transceiver
vendors, more than 50 percent of all 40 Gb/s multimode
42 I ICT TODAY
deployments are taking
advantage of this capability.
For example, a high-density
10 Gb/s SFP+ line card has
48 x 10 Gb/s ports, while
a high-density 40 Gb/s QSFP+
board may have 36 x 40 Gb/s
ports. As such, a 40 Gb/s line
card can be used to obtain 4 x 36 = 144 x 10 Gb/s ports
in the same cabling space and power consumption
conditions, thus lowering the cost and power
consumption of the 10 Gb/s single-port. These cost
savings can also be appreciated as the speeds increase
further to 100 Gb/s; there were announcements at the
end of 2018 that 400 Gb/s will start shipping this year,
both with the ability to break into lower speed
server connections.
For simplicity purposes, consider a 40 Gb/s breakout
example. Figure 2 shows three typical applications of
mesh modules in the cabling system. Four QSFP 40 Gb/s
channels (A, B, C, D) are broken out into 4 x 4 10 Gb/s
channels at the MPO input of the mesh module. The
10 Gb/s channels are then shuffled inside the mesh
module so that the four 10 Gb/s channels associated
with QSFP transceiver A are split across the four MPO
outputs. The result is that the four SFP transceivers
4x4 Mesh Module Description
TABLE 1: Mesh module.
4 x 8 fiber MPO input port, 4 x 8 fiber MPO output port
Fiber type: OS2 and OM4
SR4 vs. PSM4 meshed interconnection does not need
LC port conversion.
SFP
Transceiver
QSFP
Transceiver
QSFP
Transceiver
MPO-MPO
Transceiver
FIGURE 2: Three typical applications of mesh modules in the cabling system.