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Advantages of Chassis based Network Switches

There are a number of advantages of deploying Chassis based Network Switches in the Data Center/ Core-Distribution layers in enterprises. Chassis Network Switches are fault-tolerant, expandable and offer higher performance, among others. Let us look at what are chassis network switches, some of their advantages and limitations, in this article.

What is a Chassis based Network Switch?

A Chassis based Network Switch is a network switch that is configurable with various types of line-cards to provide the type and quantity of required network ports (copper and fiber). A chassis contains certain number of fixed slots (generally 1U each), into which various types of line cards can be inserted. The Chassis based Network Switch has a common backplane (for all line cards), has common (redundant) power supply modules, common (redundant) cooling fan modules, common (redundant) control plane/ processing modules, etc.

For example, one or two control (processing) modules are inserted into certain slots, copper/ fiber (24 port, 48 port, etc) line card modules can be inserted into the remaining empty slots and the switch can be configured as per the port requirement at any given point of time. Certain number of slots may be left empty and appropriate line cards can be inserted whenever required, in future.

Advantages of Chassis based Network Switches:

  • High Availability – Chassis based Network Switches consolidate control plane (processing unit), power supply, cooling fan modules, etc for all the modules in the chassis and hence can provide redundancy (by using additional modules in 1+1, N+1 configurations) for each of those components. One can be rest assured that single point of failure is highly reduced in Chassis based Network Switches as all the core components can be deployed in redundant configuration which mostly fails-over immediately, during individual component failures.
  • Consolidation – Since multiple units (control/ processing unit, power supply unit, cooling fans, etc) are common to all the individual line cards in Chassis switches, they offer a consolidated service that results in higher degree of efficiency/ better utilization of these units.
  • Scalability – The number of network ports supported by the switch (for example) can be increased just by adding additional line cards in empty slots. So, the system can be scaled easily.
  • Higher/ Better performance – Since Chassis based Network Switches generally feature a high speed common backplane module, more often than not, it is possible to obtain line-rate L2 and L3 switching on all ports of the entire chassis for packets of any size, resulting in a non-blocking configuration for all ports. It is difficult to realize such non-blocking configurations in individual switches that are stacked together.
  • Hot-Swappable modules – Since most of the components of the Chassis based Switches are field replaceable (and hot-swappable), it is possible to replace defective cooling fan units, control/processing unit, power supply unit, line cards, etc without bringing down the whole switch.
  • Unified Management – Since all the ports supported by the individual line cards connected to the Chassis based Network Switch are a part of the same switch, they can be managed (as a whole) using a single management application. So, configuration, maintenance and updates can be managed centrally and can be done just once for the whole Chassis.
  • Fault tolerance – Since Control, data and management planes are isolated from each other, failure of one module doesn’t affect others. Even if it does, redundancy for each of them is often built-in.
  • Network Connections (Uplink) – Generally up-links to individual line cards come from various points in the network. These uplinks can be load-balanced (if required) and made fault tolerant, by connecting multiple uplinks to various line cards and re-routing the traffic from/to one line card via another, in case of individual uplink connectivity failures.
  • Upgrades – It is possible to remove a  Gigabit port line card and insert 10 Gigabit port line card (within the limitation of the total switching capacity supported by the switch), at any point of time. It is also possible to add POE line card modules at any time. Software upgrades can be applied to a single control unit (for the entire chassis) instead of separately for individual switches, as done normally.
  • Replacement – It is easier, faster and cheaper to replace individual line cards, fan units, control units, etc than replacing entire switches.

Limitations of Chassis based Switches – Chassis based network switches have their own limitations like higher initial investment (high cost for both chassis, control modules and line cards), single vendor lock-in, larger physical footprint (hence occupying more rack space), no self-sufficient operation for individual line cards (they cannot be used without the chassis, unlike individual switches), inviability to be used in TOR (Top of the Rack) configurations in data centers and the cabling complexity involved while using them in EOR (End of the Row) configurations, etc.

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