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http://www2.sea.siemens.com | FAQ - Switches | 2007-10-01
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A: A managed switch lets you take control of your network and all the traffic moving through it, while an unmanaged switch simply allows Ethernet devices to communicate with one another. Unmanaged switches use a protocol called "auto-negotiation" to agree upon certain communication parameters. One parameter they negotiate is the data rate — generally 10 or 100 Mbps. Another is whether to use half-duplex or full-duplex mode. A managed switch, on the other hand, does all of this while also providing the flexibility of being able to adjust the communication parameters of each port on the switch to any setting you desire. This gives you the option of monitoring and configuring your network in a variety of different ways and also provides you with greater control over how data travels over the network and who has access to it. Through the use of SNMP (Simple Network Management Protocol) you can view a multitude of network statistics. This includes the number of bytes and/or frames transmitted and received, errors generated, and port status. Statistics can be viewed for each individual port in the switch
A:Star topology: Star topology is characterized by the use of a central star hub or hub resp. switch. The individual network stations are linked individually with the active network components point-to-point, producing star network topologies.
Tree topology: Tree topology is formed into a network by hierarchical in-series connection of multiple star topologies. In practice, this may consist of a combination of fiber-optics cables and Twisted Pair cables, depending on the demands placed on the individual transmission links.
Ring topology: Ring topology is created by linking the two line ends of an active line topology to a physical ring. A special redundancy mechanism ensures that the ring topology will normally remain a logical line so that no messages will circulate. Should the ring link or active network components fail, the mechanism ensures quick availability of a substitute link in the ring. The network does not fall into two segments. The effects of a network component failure are thus limited to the failed component and the terminals interfaced to it. When a ring link is interrupted by e.g. a wire break, communication continues to function without interruption.
A: Ethernet switches can have either be a FD or HD port. With Full Duplex switching one can send and receive data at the same time. With Half Duplex switching one can send and receive but only one-way at a time.
A: Standard Ethernet is the original that runs at 10 Mbaud/s. Fast Ethernet is 10 times faster than standard Ethernet and runs at 100 Mbaud/s. Gigabit Ethernet is 100 times faster than standard Ethernet and runs at 1,000 Mbaud/s. Gigabit Ethernet is generally used for high-speed backbone architectures that are required to handle a large number of devices on the network.
A: In a hub every data packet received on one port is automatically sent out to all the other ports on the hub. A hub makes no decisions about traffic direction. A switch actively looks at the data packets it receives and based on the destination address it will direct that data packet only to the port needed.
A: Simple Network Management Protocol is a standardize protocol for transporting network management information. SNMP allows addition of network management functions to a device for example an Ethernet Switch. Managed Ethernet switches offering SNMP allow users to receive various diagnostic, performance statistics and configuration parameter data from the network. These statistical and configuration parameter data is kept in a database described by Management Information Base (MIB). Users can use this diagnostics information of the Ethernet network in a SCADA system, for example, Siemens WINCC Flex (SNMP OPC Server).
A: To have redundancy in a ring structured network, one switch has to be configured as the redundant ring manager. If any segment of the primary communication path is broken or disconnected, a redundant ring manager switch will reconfigure and provide a redundant path. With recovery time of less than 300ms, one won't notice any network failure and critical applications are protected from any network interruptions. Siemens Scalance X400 and X200IRT siwtches have an integrated redundant ring manager.
A: Auto-negotiation is a procedure standardized by IEEE 802.3 in which the transmission parameters (for example 10/100 Mbps, full/half duplex) are negotiated automatically between the devices.
A: Latency specifies the time taken by frames to pass through a switch. This does not include the time required for buffering frames.
A: 10Base stands for 10Mbps base band twisted pair system of Ethernet cabling. The Standard is widely known as Category 5 Unshielded twisted pair or Cat 5 UTP for short
A: 10BaseF stands for 10Mbps Base band Fiber Optic system of Ethernet cabling.
A: 100Base-TX is just like 10baseT…uses Cat 5 UTP….RJ-45 connector….max 100m…however it can carry signals up to 100mpbs…much faster than 10BaseT. This is what is called Fast Ethernet. Fast Ethernet technology is standardized under the 802.3u
A: 1000Base-T is much like 100Base-TX…it can utilize cat 5 UTP and RJ-45 connectors, however it can carry signals up to 1000 mpbs…much faster than 100BaseT.
A: VLAN is a switched network that is logically segmented by functions, project teams, or applications without regard to the physical location of users. For example, several end stations might be grouped as a department, such as engineering or accounting. When the end stations are physically located close to one another, you can group them into a LAN segment. If any of the end stations are in different buildings (not the same physical LAN segment), you can then group them into a VLAN. More specifically, VLANs can be seen as analogous to a group of end-stations, perhaps on multiple physical LAN segments, that are not constrained by their physical location and can communicate as if they were on a common LAN.
VLANs logically segment the network
VLANs improve the performance of the network because broadcast traffic is kept local
Main Advantages of VLANs
Can divide the network into ‘switched’ separate broadcast domains for increased performance without the use of routers (routers are more complex to manage and add more overhead since they operate at layer 3 of the OSI model)
Ease of configuration
Ease of device movement without changes to the device
Lower cost per port (routers are more expensive than switches)
A: Port Mirroring allows one to monitor traffic on a network by copying traffic from monitored port to the mirror port. This can improve the performance of a network because it allows one to monitor network for problems. Traffic analyzers can capture all traffic on the network when used with port mirroring
A: IGMP (Internet Group Management Protocol) snooping automatically controls which ports receive specific multicast traffic. It stops device from becoming overwhelmed with unwanted multicast traffic
A: The power supply unit to supply SCALANCE Switches must comply with NEC Class 2 (voltage range 18 - 32 V, current requirement 350 mA). Never connect SCALANCE Switches directly to AC voltage or DC voltages higher than 32 V DC.
A: The signaling contact is connected to a 2-pin plug-in terminal block. The signaling contact (relay contact) is a floating switch with which error/fault states can be signaled by breaking the contact.
The following errors/faults can be signaled by the signaling contact:
The failure of a link at a monitored port.
The failure of one of the two redundant power supplies.
The connection or disconnection of a communication node on an unmonitored port does not lead to an error message.
The signaling contact remains activated until the error/fault is eliminated or until the current status is applied as the new desired status using the button.
When the device is turned off, the signaling contact is always activated (open).
A: The advantage of the MDI /MDIX autocrossover function is that straight-through cables can be used throughout and crossover Ethernet cables are not necessary. This prevents malfunctions resulting from mismatching the send and receive wires. This makes installation much easier for the user. All SCALANCE switches support the MDI / MDIX autocrossover.
A: All Scalance Managed switches are offered with an option of adding a 32MB EPROM for storing the configuration or application data. The memory module is called the C-Plug or the configuration plug. This C-Plug offers fast replacement of devices in the event of failure thus reducing reduces downtime
A: Multicast may floods the network without the use of proper functionality in the switch. The basic principle of multicast is that a provider sends information to multiple consumers at the same time. Usually just one consumer needs the information, but with multicast every consumer gets the information, even though it is not needed. This causes a lot of unneeded network traffic, and the need for network management features. The functionality that is required when using multicast is called IGMP snooping. Currently the X400 family of Scalance Switches support IGMP snooping.
A: The following Scalance Switches have an integrated redundant ring manger
Scalance X414-3E
Scalance X408-2
Scalance X204IRT
Scalance X202IRT
A: The following Scalance switches have single mode fiber ports,
Scalance X206-1LD: Six (10/100Mbit/s) RJ45 ports and one single mode fiber optic port
Scalance X204-2LD: Four (10/100Mbit/s) RJ45 ports and two single mode fiber optic ports
Scalance X414-3E and X408-2 offer two single mode fiber ports through the media modules #MM491-2LD (100 Mbit/s) or #MM492-2D (1Gbit/s)
A: Yes, the X208-PRO is an IP65 rated managed switch with eight 10/100 Mbit/s M12 ports.
A: The digital inputs can be used to connect a temperature sensor or a door contact for a control panel, the X414-3E switch can be configured to send a trap/E-mail, if the ambient temperature becomes too high or if someone opens the door of the control panel.
A: The X414-3E offers Layer 3 functionality (IP routing).
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