Why Manageable Switches are required even and especially at the Network Edge
This article gives an overview of why manageable switches are required, what features set them apart from unmanaged switches, and why you might want to invest a little more to accommodate managed switches even and especially at the network edge – switches which you use to connect the PC’s.
Actually, managed switches are not mandatory to make a computer network. Inexpensive unmanaged switches are sufficient in many smaller networks. The network would work just fine. But maintaining and trouble-shooting such a network becomes very cumbersome = that’s why many companies investing in managed switches even at the network edge. Let us look at some features offered by managed switches which differentiate them from their un-managed counterparts and justify the extra investment.
1. VLAN: This one is easy to guess. A manageable network switch allows the administrators to segment their network in to multiple smaller ones in order to restrict the broadcast domain. A PC or a server generally keeps communicating with every other PC/ server through broadcast packets (like ARP resolution packets etc) at regular intervals. So, if you have a single large network (running in to hundreds of PC’s, then these broadcast messages becomes so cumbersome that they can slow down the network. In such cases, it is better to restrict the broadcast domain so that these broadcasts are restricted to a smaller number of devices. A VLAN also gives an additional layer of security as the members of one VLAN cannot access the files of the members of another VLAN. Of course, exceptions can be created and Inter-VLAN routes/ multiple VLAN registration of a single port can be specified to access common resources like printers etc. It is also difficult for malicious files like viruses to spread from one VLAN to another.
2. Port Security: A manageable switch allows an administrator to enable or disable individual ports – this is very useful in case if a hugely broadcasting port needs to be shut down, without physically removing the cables or if unused ports needs to be locked.
3. Authentication/ Access Control: A manageable switch allows connection of devices based on their MAC addresses. So, administrators can specify a list of MAC addresses which can connect to the switch and even individual ports can be statically configured to allow devices with specified MAC addresses or the same can be dynamically learned (initially, up to a point of time) after which the port is locked to other devices. Some switches also integrate with Radius servers to enable 802.1x User-name/Password based authentication for individual users.
4. Web-browser based Management Interface: Manageable switches can be assigned with a unique IP address and hence can be accessed from a remote location (via a standard web browser over the internet) to monitor/ make any changes in the configuration. This remote management capability enables an administrator to remotely look in to, and make any changes to the switch configuration.
5. Cable visibility: Some manageable switches find out and display information about the cables connected with each port like approximate cable length, whether the cable is connected to the port or not, if the cable is shorted, if the cable is connected to switch only and the other end is open, approximate distance at which there might be a cable fault, etc.
6. Network performance monitoring (SNMP/ RMON Statistics): Manageable switches allow Network monitoring systems to monitor the performance of the devices connected to individual ports in the switches using the common and open-standards based SNMP protocol or RMON protocol which helps in planning for network resources, network fault diagnosis, trouble shooting etc using performance tuning data/ statistics.
7. Quality of Service (QoS): The QoS parameters are critical for real time applications like voice/ video to run smoothly even in demanding network conditions. QoS allows an administrator to specify which type of data packets need to have greater precedence when traffic is buffered in the switch due to congestion. In such cases, the high priority data traffic queues will be transmitted before those in the lower priority queues. QoS can be specified by individual ports or by layer 2(802.1p)/layer 3(TOS or DSCP) parameters where the prioritization can be implemented based on the application / IP port numbers. automatically or manually.
8. Rapid Spanning Tree Protocol support: Rapid Spanning Tree Protocol (RSTP) or its variants enables to have additional alternate cabling paths for redundancy while containing/ preventing any infinite loops that might arise by having such circular connections. Actually RSTP identifies alternate routes, if any, and keeps only one of them active at a given point of time. Once this primary route fails, or network topology changes, the alternate route for transferring data is taken automatically without noticeable delays.
9. IGMP Snooping: Manageable switches utilize a feature called IGMP Snooping to prevent multicast messages from chocking the network. This especially applies to bandwidth intensive applications like video which creates bandwidth hogs when broadcasted simultaneously to multiple users.
10. Port Mirroring: Some manageable switches have a feature called Port mirroring where a single or multiple ports are mapped to a single port in the switch and all the traffic passing through those ports are replicated in the mapped port. This enables applications like Intrusion detection, voice call logging etc.
11. Rate Limiting/ Rate Setting: Many manageable switches allow to limit the maximum rate of data traffic transmitted or received in an interface. This prevents a hugely broadcasting station, for example, from choking the entire network and prevents some network attacks like Denial Of Service attacks etc. Some switches even allow for setting the minimum commited rate of bandwidth that a particular port be allocated at all times – useful for critical users in the network. Manageable switches also allow to fix the transmit and receive rates of individual ports (like 10 Mbps or 100 Mbps etc) which can be useful for applications like Link Aggregation where the speeds of ports at both sides needs to be same.
12. Auto MDI/MDIX and Stacking: The MDI/MDIX ports are selected automatically, some ports can be configured as trunk ports, VLAN trunks etc. Some manageable switches can also be stacked together using stacking cables and stack ports which makes multiple switches to behave as a single switch with a higher data throughput capacity between them.
13. Link Aggregation: Administrators can configure multiple links between two manageable switches to increase the uplink throughput between them (Eg. 2 Gpbs with two individual links aggregated together instead of 1 Gpbs with one link). This feature can also be used with some servers with dual NIC cards to increase the bandwidth between the server and the switch. In both the cases, the additional link(s) can also be used for link redundancy (in case of failure of the primary link).
I have mentioned some reasons why manageable switches are required even at the network edge (they are more readily accepted at the core, distribution layers). If you have any points to add for or against the topic, you are welcome to do so in the comments section below.
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