Local Area Networks
The Network is the System
The low cost and high availability of fast broadband networks means that even the smallest company can now deploy advanced networking applications that before, only the largest company could cost justify. Applications such as Voice over IP (VoIP) and video conferencing can can now improve business productivity and reduce costs for even the smallest business.
But running real-time applications such as voice and video can place great strains on your local area network. Unless you introduce the appropriate traffic controls that can prioritise and limit the packet rates, voice can become unintelligible and video streams can start breaking up.
ASCTEC can help you build a reliable and resilient local area network based on advanced managed switches which provide all the traffic controls needed to exploit real-time applications such as voice and video. ASCTEC has years of network design and installation experience which can help you improve your business productivity and reduce your costs.
Managed vs. Unmanaged Switches
You can now buy a 5-8 port Ethernet switch in most computer shops for between £20 to £30. While OK for connecting a few PCs, it will not work well for larger networks using time-critical applications such as voice and video or centralised servers. For this, a more intelligent managed switch is needed. A managed switch gives the right levels of traffic control, network performance, security and reliability needed in such an environment. It typically comes with the types of features not found in cheap unmanaged switches as shown in the comparison table below.
| Features | Unmanaged Switch | Managed Switch |
|---|---|---|
| Ports | 5-24 10/100 Auto-MDIX Ethernet ports | 8-24 10/100/1000 Auto-MDIX Ethernet ports + optional pluggable interfaces for fibre and Gigabit options |
| Cooling | None | Auto-sensing and often temperature controlled |
| VLANS | None | Configurable IEEE 802.1Q VLANs |
| Routing | None | L3 Switching |
| QoS | None | Traffic prioritisation, rate limiting, ACL filtering, multicast control and buffer queuing |
| Management | Plug-and-play | Web or GUI based management tool |
| Security | None | IEEE 802.1x, TACACS+, RADIUS |
| Port Trunking | None | Port trunking using LACP |
Why use a Managed Switch?
Amongst many other benefits, a managed switch lets you:
- Limit broadcast traffic and increase security using VLANs
- Remove traffic bottlenecks using port trunking
- Guarantee bandwdith for time-sensitive voice and video traffic using Traffic Prioritisation
VLANs
One of the great things about Ethernet is that it is plug-and-play. Just plug the devices into a switch and they will find each other and start talking to each other. Ethernet achieves this by continually broadcasting messages to all the other devices connected to the switch and throughout the local area network. For a small network this may not a problem but once you start to connect 50 or even 500 devices, this broadcast traffic can really slow down and degrade the network.
To reduce the amount of broadcast traffic a network can be segmented into Virtual LANs (or VLANs). In effect, each VLAN operates as separate local area network. Members of a VLAN can only talk to other members of the same VLAN as shown in the diagram below. This not only reduces the overhead of broadcast traffic, but also gives added security between the various VLANs. For instance, a shared file folder in one VLAN will not be visible or accessible to another VLAN.
VLAN Switching
Traffic that needs to go between differnet VLANS, for example between VLANS A, B and C in the example above, is processed through a routing function in the managed switch. This is often known as L3 Switching.
Port trunking
The connection to a shared network resource such as a database or file server can often become a network bottleneck. Even if you put in a Gigabit Ethernet connection, it only takes 10 users with 100 Mbps Fast Ethernet connections accessing the server simultaneously to saturate it.
Port Trunking
Port trunking is a technique where you can bundle one or more connections together to build a bigger, fatter pipe.For instance, in the diagram above, multiple Gigabit links are bundled together to double or quadruple the available bandwidth.
Traffic prioritisation
Voice and video applications do not actually use a lot of bandwidth: voice typically needs 100 Kbps per call and video about 500 Kbps. What they do need is predictable bandwidth with low delay and jitter.
A QoS-enabled Managed Switch can be used to:
- Define multiple classes of traffic using IEEE 802.1p. These can be used to identify and allocate bandwidth to: realtime traffic, business critical, data transfer and best-effort traffic.
- Rate limit the traffic so that high volume data does not swamp the network. For example, a video streaming session can be rate limited to the speed that the receiving stations are able to process the video stream rather than building up buffer queues by sending it all at once.
For more information about ASCTEC's Managed Switch solutions, please contact us.
