Unmanaged Edge and Managed Layer 2 Edge switches are being
used in hardened environments such as industrial, transportation, oil fields and
Intelligent Transportation Systems (ITS). These manufactures have seriously engineered
those switches for sustainability in rugged environments. Similar to the enterprise application, the
switches are being used for high-speed connectivity between end nodes at the
data link layer.
Unlike an Unmanaged Edge switch, the
Layer 2 switch uses bridging technology to segment the local area networks (LANs)
at the data link layer level and intelligently control the flow of data traffic
in an organized way. A multiport switch
typically learns about the Media Access Control (MAC) addresses on each of its
ports, stores those MAC addresses in the MAC address table and then transparently
passes Layer 2 data frames destined to those ports. When a switch receives a message sent from an
end node (host) the switch checks its MAC address table for the destination
address. The switch ensures that the unicast frames destined for MAC addresses
that lay on a port can only receive the frames and not forward them to all of
the other ports. Therefore, the Layer 2
switch transfers the appropriate data frames to the appropriate network devices
efficiently and helps to increase network bandwidth. The Layer 2 switch creates a separate
collision domain (segment) per switch port and each port provides dedicated
bandwidth. Whereas, an unmanaged edge
switch or hub has a single collision domain (segment) that allows data frames
to be sent to all of the ports except the port that originally received it. In addition, the Layer 2 switch offers many
advance features for network redundancy, logical LANs segmentation, and
security. In this blog, I am going to talk about network logical
LANs segmentation and introduction to Inter-VLANs network design consideration.
By default, the Layer 2 functions as single network segmentation
typically designed as a broadcast domain network. Within this network design, every broadcast
packet transmitted is seen by every device on the network regardless of whether
the device needs to receive that data or not. It works for a small home and office network
but is not recommended for medium to large size networks of multi-level devices
types, reliability and security applications. The figure below shows how basic
Layer 2 switch works in this particular design. Host A sent a broadcast package into the
network that all of the devices within the same network segment receive. 
The key benefit of using LAN segmentation within Layer 2 switch
networks is to create more and smaller LANs to reduce network collision and
broadcast storms in the same segment. Virtual LAN (VLAN) is a method of
logically segmenting a network by grouping network devices into different
sub-networks. One of the advance
features in Layer 2 switches allows us to group switch ports to sub-group without
the limitation of physical location. This logical segmentation increases security
and broadcast management. In a VLAN,
broadcasts and any other type of communication data are VLAN specific to the
same VLAN. Members of VLAN A will not
receive broadcast or send data to a member of VLAN B. The figure below shows the logical
segmentation on the Layer 2 switch network design by using VLANs.
VLANs can span multiple switches by using VLAN trunking
protocol (Cisco ISL or IEEE 802.1Q) on each switch in the network. Figure below shows the logical segmentation on
multiple Layer 2 switches.
Since VLANs are separate network segments, members in a VLAN
require a router or Layer 3 switch to communicate to other members in different
VLANs. Layer 3 switches are routers with
fast forwarding done via hardware instead of software like router does. IP
forwarding typically involves a route lookup in the routing table. Similar to bridges, switch routers create
separate collision domains on each segment connected to the router, but unlike
bridges or switches, routers do not forward broadcast traffic by default. Therefore, routers create separate collision
domains and also separate broadcast domains on each segment. Figure below shows the VLANs network with a
Layer 3 switch or router. Now all
members of different VLANs can communicate to each other via the routing table.
In conclusion, this typical network design is being used
mostly in Intelligent Transportation Systems.
More and more legacy hardware and software are being used in transportation.
Components such as ATMS software, signalized traffic controllers, vehicle
detection, video surveillance, and dynamic message signs with real-time
traveler information etc. are a few examples. These ITS technologies depend on reliable network communication systems for
real-time data communication between Traffic Management Center (TMC) software
and field legacy network devices to increase efficiently and improve air
quality by reducing traffic congestion, travel time, and fuel consumption. ITS network communication systems are
designed to meet performance, reliability, scalability, availability, and
security standards.
