LAN Switches: A Trend Worth Following…

Aswitch is a special type of hub that forwards packets to the appropriate port
based on the packet’s address, automatically learns network addresses, and
gives each sender-receiver pair the full bandwidth of the network. A switch
segments networks into different subnets, thus keeping the network from being
overloaded with traffic.

Typically, a switch can either be unmanaged or managed. A managed switch can
either be a stackable switch or a chassis switch.

Layer 5
Switches Gain Popularity

The layer 5
(L5) switch aims to use session level information in addition to layer
2-3-4 information to route traffic in the network. The L5 system consists
of a switch core to which a number of custom- built intelligent port
controllers are attached. In addition, it is equipped with a processor
complex. The job of the port controllers is to identify the packets that
require layer 5 processing and forward them to the processor. The port
controllers process the rest of the packets. As the CPU processes only a
very small fraction of the packets, it achieves very high speeds while
delivering useful layer 5 functionality. In fact application level
proxies, which are functionally equivalent to the L5 switch, have been
around for years. L5 combines the functionalities of an application layer
proxy and the data handling capabilities of a switch into a single system.
Though it can be used anywhere in the network the L5 switch is most useful
as a front-end to a server cluster. It makes it possible to partition the
URL space among the server nodes thus improving the performance of the
server cluster.

n Unmanaged
The unmanaged standalone switches are gradually replacing hubs in
most networks. These switches allow simultaneous transmission of multiple
packets via an internal high-speed data channel. The learning function in the
switch stores the address and corresponding port number of each incoming and
outgoing packet in a routing table. This information is subsequently used to
filter packets whose destination address is on the same segment as the source

A typical unmanaged switch comes with the following features:

  • Automatic detection of MDI-X and MDI crossover
  • Conformation to IEEE 802.3 10BASE-T and IEEE 802.3u 100
    BASE-TX specifications

  • Store-and-forward scheme to forward packets

  • Frame filtering and forwarding for each port

  • Automatic MAC address learning and aging

  • Automatic local traffic filtering

  • Auto-negotiation on duplex mode

n Stackable
The stackable switches are those where different standalone
switches are combined to perform the function of a single large switch.

A typical stackable switch comes with the following features:

  • Fault tolerance so that if one switch fails, the other
    switches in the stack can continue to operate

  • Port redundancy so that if one port fails, a backup port
    can be automatically substituted

  • Hardware/software to let the user manage the switches
    using the Simple Network Management Protocol

n Chassis
These are much larger with several chassis/line cards, each having
several ports.

In addition, switches are also classified by the
functionalities of the layers of the OSI model of networking.

n Layer
2 switches:
These are manageable switches that enable an administrator to
monitor the traffic passing through each port and to configure each port in the
switch. Besides, a typical layer 2 switch comes with the following features:

  • IEEE 802.1D Spanning Tree support

  • GVRP (GARP VLAN Registration Protocol) support for VLAN
    membership management

  • IGMP snooping, to prevent broadcast traffic from flooding
    to all the ports within the switch.

  • Link aggregation to improve the uplink traffic
    performance and provide link redundancy.

  • IEEE 802.1Q/p support for VLAN and priority



Cisco Systems









n Multiple
Layer Switches:
Switches support multiple layers (2, 3, and 4) protocols to
protect against obsolescence and to add new services such as traffic
classification, protocol filtering, and multicast to handle and prioritize
different types of traffic.

A typical multilayer switch has the following features:

  • Supports RIP v1, v2 and OSPF routing functions.

  • Supports multi-netting assigning multiple IP protocol
    interfaces to the same physical port

  • Supports classless inter-domain routing (CIDR) to enable
    the efficient allocation of the IP address space

  • Serves as DHCP server or client or relay

  • Serves as DNS server or proxy

  • Access control list for enhancing security purpose

  • Bandwidth management for better usage


n Proper Assessment:
It is imperative to have a proper assessment of the LAN requirements of an
organization. One important aspect to be kept in mind is the sort of
applications that are normally used, as the LAN capacity/speed would be
dependent on that.

One should keep in mind the layer/level of the LAN where the
switch is going to be deployed. A chassis switch would be better deployed in the
head office, while a stackable switch would be better in the branch offices.

n Upgradation
Multilayer switches are upgradable, but not beyond layer 3. In case
of organizations using multimedia applications, it is advisable to go for layer
4-7 switches.

n Enhancing
A switch will improve performance for any file servers or
workstations connected directly to it. Small network can use a switch instead of
a hub to give workstations maximum speed. If a network is large, it should have
at least one switch in every high-traffic workgroup. As a general rule, try to
get every file server, critical workstations, and print server connected
directly to a switch.

n Running
High-speed Applications:
When a network will be using high-speed
applications like multimedia or video generally speaking, every workstation and
file server that will be using multimedia or video should be connected to a
switch to avoid transmission delays. Anywhere a 10/100 Fast Ethernet hub is
required small workgroups and large network alike will benefit more from using a
10/100 switch to maximize performance over a mere 10/100 hub alone.

n Full Duplex:
16 or 24-ports switches should run at 10/100 full duplex and have an auto
sensing capability

n Seamless
Should be perfect for running 10BaseT, 100BaseTX and 100BaseFX
hardware seamlessly

n Data Flow
Data flow control should be able to filter out faulty data packets

n Data Packet
Must be capable of advanced store-and-forward data packet

Market Information

The movements in the telecom space were also responsible for the switches
market being the most vibrant in the last fiscal. The total switches market in
the country has grown from Rs 798.7 crore in the last year to Rs 960.4 crore
this year, growing by 20 percent. Cisco has a 65 percent share of the switches
market too, with the main competition coming from Intel, Cisco and D-Link. In
the high-end chassis-based Layer 3 switch category, the main competition was
between Cisco and Enterasys, while Nortel dominated the Layer 4-7 segment.

The market witnessed compartmentalization of switches into various
categories. In terms of numbers, unmanaged fast Ethernet switches were sold in
large quantities. Among managed switches, 24 port switches were the most

The layer 3 switches sales did not really pick up. Even now there are more
layer 2 switches being sold than layer 3 switches.

This is because it is not very easy to configure the layer 3 switches. The
layer 3 market in India itself is not very well defined.

What a network needs is a high backbone coupled with a non-blocking
architecture, and only then will the features of the switch be best exploited,
be it layer 3, 4 or 5.


manager, D-Link
Cisco Systems
president, Nortel Networks

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