Perle Systems P840 manual Aging Timer

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Introduction

Forwarding

Once the initial learning process is complete, the bridge/router enters a forwarding mode and examines frames that may need to be forwarded. The learning process does not stop at this time, however: The bridge/router will continue learning new stations as they become active on a LAN segment.

Local Destination Addresses

When a frame is received from a station on one segment, the frame is examined for the source address to ensure that this station has already been entered into the address table. If the source address exists, the Ethernet destination address is then viewed. The bridge searches the previously built address table for the location of the destination station. If it is determined that the location of the destination station exists on the same LAN segment (i.e. the destination address is local and the frame does not need to be forwarded across the bridge to the other LAN segment), then the bridge will “filter” and discard it.

Initially, the bridge will only recognize those addresses that are local to a specific LAN segment. The bridge will thereby filter (discard) all local packets and forward all unknown non-local packets to the second segment located on the outbound port across the bridge.

Forwarding Unknown Destination Addresses

When a frame is received from a LAN segment with an unknown destination address (an address that does not yet exist in the filter table), the bridge will forward the frame to the other segment, logging the address, and marking the location as “unknown.”

Unknown Location Update

When the receiving station transmits a frame in the opposite direction, the bridge will now see the previously unknown destination address in the source address field. It will now process this source address as it did during the initial learning stage, adding the location to the address entry.

In this fashion (looking at source addresses of non-local packets), the bridge learns about non-local stations and their associated arrival ports. The bridge then updates the location of each address in its table. In the future the bridge will look up these stored non-local addresses to determine the bridge port on which to forward a packet destined for a known non-local station.

In summary, the P840 router will “learn” the location of a station by examining the source Ethernet address, and will “filter” frames based on destination address. A frame received from one segment that is of “unknown” location will be forwarded to the other segment. A frame that is received with a source address equal to a known address, but previously marked as an unknown location, will be updated in the filter table to add the location.

Aging Timer

During the bridging process, the filter table is built giving the location (bridge port or LAN segment) of known Ethernet addresses. The table would become quite large, eventually reducing performance, if stations were added, removed, or moved without the old information being purged periodically. Performance is affected since the larger the table, the more time it will take to process an incoming frame.

This purging process, called “aging,” is an integral part of the learning function. It limits the size of the filter table and ensure that performance is not reduced unnecessarily.

Aging assumes that many of the addresses may not be active all of the time, and could be purged after a specified interval to keep the size of the filter table small. In general terms, the smaller the table, the higher the performance.

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Contents Perle P840 P840 Router IntroductionARP-Address Resolution Protocol IP Routing and the P840 RouterProxy ARP Complete IP Connection IP Header Details Unreachable Icmp MessagesRedirect QuenchRIP-Routing Information Protocol Update MechanismPing Time and Mask serverBridging and the P840 Router Initial Bridging ProcessStation Address Learning Aging Timer Filled Address Table Address PurgingAging Exception P840 Router Feature Definitions TelnetLink Compression Typical Compression Ratios by File Type Bandwidth On Demand WAN TopologiesMultilink MultipointTime of Day Connect Application Operating Software UpgradesP840 Isdn Connection Management Wide Area Network Topologies SupportedCall Establishment Methods Auto-Call Time-of-Day Connections Isdn Connection ManagementManual Call Address ConnectCombination Connection ProcessProtocol Awareness Idle TimerSuspension Process Interesting TrafficSuspended Server P840 Session Participation SpoofingTermination Process IP SpecificsIP Address Connect Suspension of TCP/IP SessionsPinout Information Console ConnectorEvent logs Event LogsEvent Logs Event Logs Event Logs Event Logs Event Logs Alarm logs Event Logs Event Logs Event Logs Code Description Code Event Logs Event Logs Event Logs Event Logs Event Logs PPP Security logs Security MAC Address FilteringSecurity-Filter if Destination FilteringSecurity-Filter if Source Security-Forward if Destination Security-Forward if Source FilteringFiltering Pattern Filter Operators Bridge Pattern FilteringProtocol Discrimination Internet Protocol IP Protocol Type FieldFilter all IP Packets IP, and no moreFiltering Filter only TCP/IP Transport Control Protocol / Internet Protocol TCP/IPFilter all IP without TCP traffic Filter all except TCP/IPFilter all DEC Bandwidth ConservationEthernet Broadcasting Ethernet MulticastingGeneral Restrictions Internet AddressesEthernet Station Addresses Mask would be 6-010203040506&12-0800&23-06 Example Mask CombinationsIP Router Pattern Filtering Frame Formats Ethernet Type Codes Octet Locations on an IP Routed TCP/IP Frame Octet Locations on a Bridged XNS Frame

P840 specifications

Perle Systems is renowned for its high-performance networking hardware, and the Perle P840 model exemplifies this reputation with its advanced features and technologies. Designed for small to medium-sized enterprises, the P840 serves as a versatile and reliable solution for connectivity needs.

One of the main features of the Perle P840 is its robust network performance, supporting both Ethernet and serial connectivity. With support for RS-232, RS-422, and RS-485 interfaces, the P840 enables seamless integration of legacy devices into modern network architectures, allowing businesses to leverage existing infrastructure without the need for extensive upgrades.

The P840 also boasts advanced security features to protect sensitive data during transmission. It supports SSL encryption and VPN capabilities, ensuring that data travels securely across the network. Additionally, it implements strong authentication protocols, providing organizations with peace of mind knowing that their communications are safeguarded against potential threats.

Another standout characteristic of the P840 is its flexibility in configuration. It offers multiple port configurations, allowing for customization based on specific user needs. With options for both managed and unmanaged modes, the device can easily adapt to various network environments. This flexibility makes it suitable for diverse applications, including industrial automation, process control, and telecommunications.

The Perle P840 is designed for durability and reliability, featuring a rugged enclosure that can withstand demanding environments. Its solid-state components reduce the risk of failure, contributing to increased uptime and lower maintenance costs. Furthermore, the compact design allows for easy installation in tight spaces, making it a practical choice for various deployment scenarios.

In terms of management and monitoring, the P840 includes an intuitive web-based interface, enabling administrators to configure settings and monitor network performance effortlessly. SNMP support further enhances management capabilities, allowing for integration into larger network management systems.

Overall, the Perle P840 stands out as a powerful solution for enterprises seeking seamless connectivity, robust security, and flexibility in configuration. Its combination of advanced features and durable design makes it an ideal choice for industries requiring reliable serial and network connectivity in challenging environments. With the P840, businesses can build a resilient networking infrastructure that supports their growing demands while safeguarding their critical data.
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