Redundancy architectures - Ring preferred with a separate control channel

Rapid Spanning Tree Support

Automatic Topology Generation

Ease of Installation  and Configuration

Ease of monitoring  the switch with useful network diagnostics

GOOSE Messaging for Power Utilities

QOS. VLAN's

Access Control Lists (ACL filtering)

SNMP Support

SNMP Management -  Features and Uses

SNMP Features

Managed switches should be a major consideration if the health and operating condition of the network is important. A managed switch supports SNMP v1, v2, or v3 and it allows network operations to communicate with network management packages. This requires greater intelligence at the switch. There is a wide variation in the performance of SNMP metrics in Industrial switches. Kyland has the very high performance metrics in its network management. There are several companies are misleading customers by calling switches that have a web-server or answer to specific SNMP queries as 'smart' or 'managed'. Several vendors state that SNMP is a security risk, implying that, although this is a standard method for all applications, it is a problem for automation applications. This is absolutely false. A quick examination of the vendors products will show that these vendors do not have SNMP capability in their switches to try to reduce costs.SNMP Management is a world wide IEEE Standard, and is designed to operate with a variety of Network Management Systems (NMS)

Kyland Industrial Ethernet switches operate as fully managed, and standards based SNMP switches with superior performance.

IGMP Snooping

With Unicast traffic, the switch learns the MAC address by looking into the source address field of every frame. With Multicast packets, the switch must deal with a multicast MAC header, which may or not appear in its Bridging Table. As a result, multicast packets are copied and transmitted ( 'flooded' ) to every port of the switch. During 'Multicast Floods', devices are unable to use the network, preventing control data from being sent. The effect of 'Multicast Floods' is particularly serious with full duplex links, because the bandwidth used is proportional to the number of attached nodes - each of which invites a multicast packet. IGMP Snooping prevents a flood of packets from 'flooding' a network segment where a node is not interested in receiving the packets. IGMP is an integral part of IP and is used by Layer 3 switches ( routers ) to report their multicast status to nearby routers. Because a router must look into the MAC header and 'snoop' into the IP header before handling the packet, this capability is called 'IGMP SNOOPING'. The multicast packet is then directed only to those nodes listed in the router's table of learned multicast addresses said to be interested in receiving the traffic.Kylands Patented IGMP Snooping and Packet Control delivers better network performance,

GMRP ( GARP Multicast Registration Protocol )

GMRP is employed to configure switch ports dynamically to forward IP multicast traffic reports used by Multicast Hosts.

VLAN ( Virtual Local Area Network )

A Virtual LAN is a way that allows switches to create a single Collision Domain logically even though the nodes are on separate network segments physically. The benefit is that instead of physically installing hardware to segment a network, VLANs can do it through software. VLAN configuration can be based on port ID, MAC or IP addresses. The Port based VLAN standard is IEEE 802.1q. Each switch in the VLAN must be able to implement the port based VLAN policy. Ethernet Direct switches support IEEE 802.1q port based VLANS. Kyland is one of the few industrial ethernet vendors that supports all three types of VLAN segmentation in an easy to use method of switch configuration. 

RMON ( Remote Monitoring Protocol )

RMON is an alternative to SNMP that transfers the monitoring responsibility to the managed switch, rather than to the Network Monitoring Software station. The switch can transmit data at convenient times and send alarms to the station without waiting to be polled.

MIB ( Management Information Base )

MIBs are a database maintained by the SNMP package that logs the device's condition and the traffic through the device. The IETF has defined MIBs for ethernet switches.MIBs are critical to interoperability. The Network Management System (NMS) talks to the device through SNMP, but pulls information from the switch's MIBs. A common SNMP and MIB structure make it possible to operate different vendors' switches on the same network because the NMS can work with a common interface. Kyland Industrial Ethernet switches incorporate SNMP V1/V2c agents and MIB-II objects. Kyland Industrial Ethernet switches interoperate with all NMS based software that can read MIB data directly.

Ring Redundancy

The use of a ring for redundancy or failure recovery is common among suppliers. Since there is no IEEE or IETF standard, each supplier has a slightly different scheme and thus, proprietary method. For this reason, many customers are not selecting ring redundancy - it would lock them into a particular supplier. That is in order to add to the ring or replace an existing device - you MUST provide the device from the original supplier. Many customers now choose Rapid Spanning Tree - it is another redundancy scheme and is an IEEE standard that can be used for most applications. Ring Redundancy must be configured in managed switches using, according to the vendor, pre-defined ports, and one switch must be defined as the 'ring manager'. Kyland supports both methods of redundancy. Kyland has its DT-Ring protocol suite ( with a recovery time of <50ms). This performance level is equal to or better than SONET failover, It is also important to realize that only Kyland has an Industrial Ethernet switch that suppots 10 Gigabit backbones. Kyland also has a switch that supports up to 12 fiber backbones.

Spanning Tree and Rapid Spanning Tree Redundancy ( RSTP )

The Spanning Tree Protocol (STP) is a link layer network protocol that ensures a loop-free topology for any bridged LAN. It is based on an algorithm invented by Radia Perlman. In the OSI model for computer networking, STP falls under the OSI layer-2. Spanning tree allows a network design to include spare (redundant) links to provide automatic backup paths if an active link fails, without the danger of bridge loops, or the need for manual enabling/disabling of these backup links. Bridge loops must be avoided because they result in flooding the network. The Spanning Tree Protocol (STP) is defined in the IEEE Standard 802.1D. As the name suggests, it creates a spanning tree within a mesh network of connected layer-2 bridges (typically Ethernet switches), and disables those links that are not part of the tree, leaving a single active path between any two network nodes.This redundancy method allows a back-up path to be put in a standby mode and activated upon failure of the primary path. The network topology CAN be in a ring - similar to Ring Redundancy.In 1998, the IEEE with document 802.1w introduced an evolution of the Spanning Tree Protocol: Rapid Spanning Tree Protocol (RSTP), which provides for faster spanning tree convergence after a topology change. Standard IEEE 802.1D-2004 now incorporates RSTP and obsoletes STP. While STP can take 30 to 50 seconds to respond to a topology change, RSTP is typically able to respond to changes within a second.^[7][8]

RSTP bridge port roles:

• Root - A forwarding port that is the best port from Nonroot-bridge to Rootbridge
• Designated - A forwarding port for every LAN segment
• Alternate - An alternate path to the root bridge. This path is different than using the root port.
• Backup - A backup/redundant path to a segment where another bridge port already connects.
• Disabled - Not strictly part of STP, a network administrator can manually disable a port

RSTP is a refinement of STP and therefore shares most of its basic operation characteristics. However there are some notable differences as summarized below:

• The Detection of Root switch failure is done in 1 hello times, which is 2 seconds if default hello times have not been changed.
• Ports may be configured as edge ports if they are attached to a LAN that has no other bridges attached. These edge ports transition directly to the forwarding state. RSTP still continues to monitor the port for BPDUs in case a bridge is connected. RSTP can also be configured to automatically detect edge ports. As soon as the bridge detects a BPDU coming to an edge port, the port becomes a non-edge port.
• Unlike in STP, RSTP will respond to BPDUs sent from the direction of the root bridge. An RSTP bridge will "propose" its spanning tree information to its designated ports. If another RSTP bridge receives this information and determines this is the superior root information, it sets all its other ports to discarding. The bridge may send an "agreement" to the first bridge confirming its superior spanning tree information. The first bridge, upon receiving this agreement, knows it can rapidly transition that port to the forwarding state bypassing the traditional listening/learning state transition. This essentially creates a cascading effect away from the root bridge where each designated bridge proposes to its neighbors to determine if it can make a rapid transition. This is one of the major elements that allows RSTP to achieve faster convergence times than STP.
• As discussed in the port role details above, RSTP maintains backup details regarding the discarding status of ports. This avoids timeouts if the current forwarding ports were to fail or BPDUs were not received on the root port in a certain interval.

Different switch vendors that support RSTP in their managed switches can be used in the same network segments - RSTP is an IEEE standard. Users must configure RSTP in managed switches - defining various aspects of the configuration.

How difficult is it to learn how to set up managed switches ?

It depends on how the switch needs to be configured - most parameters are very easy, such as:

Setting the IP address and giving the switch a name, location and description ( all optional )

Enabling the IGMP Snooping

Port Control - turning off unused ports

Security - entering the IP addresses ( laptops, desktops ) allowed for management changes

Ring Redundancy - entering the ports used for the ring

Parameters that are more difficult: you should read the manual:

VLANs

RSTP Redundancy - setting all the necessary parameters

Kyland makes fully managed, SNMP switches and serial servers. Kyland Products - "The Engineers Choice"