April 11, 2018
Top of rack (ToR) is one common architecture of switch-to-server
connections. According to a survey result in 2015, ToR was the most
popularly used architecture both in colocation data centers and
enterprise data centers.cable ducts Seen from current trend, it will be widely deployed in the present and
in the future as well.Thanks for your questions. A ToR switch could be
at the top of the rack, but the actual physical location does not
necessarily need to be at the top of the rack. It can also be at bottom
or middle of the rack. After practical installation, however, engineers
found that top of the rack is better due to easier accessibility and
cleaner cable management.In today’s leaf-spine topology, the ToR
switches are the leaf switches and they are attached to the spine
switches. For example, 10G servers are connected to a 10G ToR/leaf
switch (it has 40G ports as well) via 10G SFP+ DAC (direct attach copper
cable), or via Cat6a/Cat7 cable and 10GBASE-T transceiver. Then the 10G
switch is connected to a 40G spine switch.
The combination of ToR and leaf-spine has solved some problems that
existed in traditional three-tier (access-aggregation-core) topology,
such as the "traffic jam†in top-tier switch. In a three-tier network
topology, the data traffic will all take a single "best path†that is
chosen from a set of alternative paths, until the point that it gets
congested then packets are dropped.
In leaf-spine topology, to prevent any one uplink path from being
chosen, the path is randomly chosen so that the traffic load is evenly
distributed between the top-tier switches. If one of the top-tier
switches were to fail, it only slightly degrades performance through the
data center.Since ToR is the most popular design of data center
architecture, ToR switches naturally become popular as well. Here are
some high performance ToR switches of different switch-to-server data
rates, ranging from 1G to 100G.All these ToR switches support L2/L3
features, IPv4/IPv6 dual stack, data center bridging and FCoE. ToR
switches are often required to be multiport and the low-latency since
they have to deal with different layers’ traffic.
In present, the 1G and 10G data rates still contribute to the largest portion of all switch-to-server connections, 40G and 100G ToR switches that can support multiple data rates are still not many. The 40G example and the 100G example I listed above are one the few multiport high speed ToR switches that are with low latency and high performance.
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