3Com 1005 Intelligent Flow Management

DUA1840-0AAA01

Switch Operation and Features

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Intelligent Flow Management

Intelligent Flow Management

(IFM)

is a congestion control mechanism

built into the Switch 1005. Congestion is caused by one or more

devices sending traffic to a Switch port which is already busy. The

Switch 1005 contains both input and outp ut packet buffers and while

congestion is rare, IFM is designed to alleviate problems during those

moments when packet buffers in the Switch 1005 are full. IFM will

prevent packet loss by inhibiting the transmitting device from sending

any further packets until the port is no longer congested.

If a packet arrives at a conventional switch that does not operate IFM,

and that port is congested, the transmitting device is unaware of this

until it times out and decides that the receiving station is not going to

respond to the message. This can take as long as 30 seconds, and

depending on the protocol you are running, may not happen until

many packets have been sent. The transmitting device then has to

retransmit the packets, effectively wasting bandwidth.

Switch

modules

implementing IFM are aware of congestion, and

prevent packet loss by inhibiting the transmitting device from

transmitting the packet in the first place. It does this by forcing the

device to retransmit the packet later. This “back-off” and retransmission

happens very quickly (typically less than one second ) and is much

faster than waiting for the transmitting device to time-out. There are

two benefits:

■

the packet is transmitted quickly and successfully

■

the packet is only transmitted once, thereby saving bandwidth.

IFM is designed to be enabled on ports connected to a single network

device. If IFM is enabled on a port connected to multiple devices

through a repeater, packet congestion within the Switch 1005 could

result in packet transmission between two devices connected to the

repeater being inhibited.

Contents

Main MSH S 1005 G U Page C S D R A Page W A R G C H C M S P M A R S C S Page B U guide. The following table shows where to find specific information in this How to Use This Guide Conventions list text and icon conventions that are used throughout this guide: Table 2 and Related Publications Page A About the LinkBuilder MSH About the MSH Switch 1005 Summary of Features Port Connections Adding an Expansion Module Switch Operation and Features How the Switch Compares to a Bridge : Switch 1005 The table below shows how a packet is processed when it arrives at the To best suit your networking requiremen ts, the Switch 1005 allows you to set one of four frame forwarding modes: operate in Store and Forward mode until the error count returns to 0. 1005 detects more than 18 packets per second with errors, it will with errors, it will operate in Fast Forward mode. As soon as the Switch Intelligent Flow Management Full Duplex Security Virtual LANs (VLANs) Resilient Links PACE You can enable PACE on the whole Switch 1005 or on an in Chapter 3. Port Setup and MSH Switch 1005 on Your Network Server Connections Network Configuration Examples Figure 1-1 shows how the Switch 1005 fits into a large corporate each floor and servers are centralized in the basement. network with a Fast Ethernet infrastructure. A Switch is positioned on Page Figure 1-3 shows the Switch 1005 used for a group of heavy-traffic connected via a 100Mbps Fast Ethernet link. desktop with a single end-station per switch port. Local servers are users in a large corporate network. Here, switching is brought to the Configuration Rules for Fast Ethernet Configuration Rules with Full Duplex Switch Overview Front Panel LEDs For information on using the LEDs for fault diagnosis, please see in Chapter 6. Identifying Fault Conditions with the LEDs Transceiver Module slot 10BASE-T Ports Switch Overview PCB View Transceiver Module Connector [1] Expansion Module Fixing Posts [2] Switch Defaults : The following table shows factory defaults for the MSH Switch 1005 odule These connectors engage with the backplane located in the MSH chassis. Setting Up the MSH Switch 1005 for Management Page Page Pre-installation Configuration Before installing the Switch 1005 into the chassis, ensure it is Figure 2-1 The links are located on the Switch 1005 PCB as shown in connections. Table 2 -1 shows possible configurations for LK1 - LK5. You may have replaced with another one. the chassis is reset or powered off/on, or if the Switch 1005 module is changes made through management software. This is the case, even if Advice for Setting Backplane Connections and Avoiding Loops Considerable care should be taken when setting backplane connection in a different VLAN on each Switch. If you have implemented multiple VLANs, put ea ch internal Ethernet effectively by connecting one internal Ethernet connection to each Fitting a Transceiver Module Fitting an Expansion Module Switch 1005 Installation and Removal Installing the Switch 1005 Removing the Switch 1005 Operation after Power-up In a Managed System In a managed MSH chassis, operation of the Switch 1005 is the same, them when the MSH chassis and Management Module are powered on. Switch 1005 modules correctly when they are inserted, you must insert To ensure that the Management Module can see and configure new Setting up the Switch 1005 Using the VT100 Interface Page If you are using Telnet or a terminal emulation program you may find that some of the Control keys do not operate or that they activate other terminal emulation software before using the Control keys. functions. Check carefully in the manual accompanying your Telnet or Using Telnet Once you have specified the modules IP parameters, yo u can use any advice. have the correct MIB. Contact your local support representative for a Network Manager from another vendor, you will need to ensure you Accessing the Switch 1005 VT100 Interface Logging On LinkBuilder case-sensitive. Enter your user name and password. Note that the y are both 5 If you are logging on for the first time (after installation or initialization), use a default user name and password to match your access . Figure 2-4 Menu appears as shown in From here, you can select the options needed to manage the module. Access to options depends on the access level you have been assigned. parameters. This is described in the followi ng section. You should select the MANAGEMENT SETUP option to assign IP on page 2-21. Switch 1005 Management Setup Page Logging Off Auto Logou t If you connected to the Switch 1005 via the MSH Management Module screens, the LinkBuilder MSH Address Table screen is displayed once you have entered the correct password. Setting Up Users Creating a New User These steps assume the User Access Levels screen is displayed. monitor as secure monitor Deleting a User Editing User Details These steps assume the User Access Levels screen is displayed. advise on your next course of action. interface, contact your local technical support representative who will If you forget your password while logged out of the Switch 1005 VT100 Assigning Local Security Community SNMP The Switch 1005 can be managed important or sensitive data on your n etwork. may want to disable all access to the management facilities if there is have some simple security features, but it is an insecure protocol. You Page C Management Level , the all options relate to VLANs. and Figure3-3 Page Switch 1005 Setup Page Page Port Se tup Page Page Page Specifying the Backbone Port The Switch Database (SDB) Page Configuring the Switch Database , allows the port identifier for this entry. If an entry is highlighted in the listbox, this field shows Port Numbe r Searching the Switch Database Adding an Entry into the SDB Deleting an Entry from the SDB Resilient Links Viewing Resilient Setup Page Configuring Resilient Links Page Creating a Resilient Link Deleting a Resilient Link Setting Up Traps Community String The community string allows a very simple method transmission. gives a minimum delay of one tenth of a second between each throttle is one thousandth of a second. The default value is 100, which Resetting the Switch 1005 Initializing the Switch 1005 Page Upgrading Software Page Page M Benefits of VLANs An Example VLANs and the Switch 1005 Page VLAN Configurations Page Page Page Page Page Setting Up VLANs on the Switch Page ResBP This field displays the resilient backbone port for the VLAN, if This button applies any changes to the VLAN database. APPLY on page 3-17 Page Page Summary Statistics With the Switch Management screen displayed, choose to view have been successfully transmitted by each port. Displays the total number of frames that FRAMES TRANSMITTED Page Port Statistics With the Switch Management screen displayed, choose to view because each user will see degraded network performance. around 40% you should reconsider the topology of your network multiple end-stations are connected to this port and you see values of Page Port Traffic Statistics With the Port Statistics screen displayed, select the TRAFFIC STATISTICS boundary. preamble/SFD. Octet counters are accurate to the nearest 2 56 octet calculation includes the MAC header and CRC, but excludes Page IFM Count The total number of times Intelligent Flow Management management station. not clear the counters on the device or affect counters at the network see changes in counters over a short period of time. This button does Port Error Analysis Page Status Monitoring Hardware Version The hardware version number of the Switch 1005. case you need to quote it to your technical support representati ve. software stored on the Switch 1005. You should note this number in This is the version number of the Boo t Remote Polling Page P V Spot Checks M S Identifying Fault Conditions with the LEDs The following table shows how you can identify possible fault Appendix C as described in If you cannot solve the problem, contact your local supplier, or proceed VT100 Problems Switch 1005 Operation Problems Page Page A H access rights are read-and-write. The access rights granted to Monitor level are all read-onl y. All other accessing and editing Switch 1005 screens via the VT100 interface. Page Page Page B Page C Call the telephone number nearest you: World Wide We b Site more. articles from 3TECH (3Coms award-winning technical journal) and customer service and support, 3Coms latest news releases, selected This service features news and information about 3 Com products, 3ComForum on CompuServe , Local numbers are available within the following countrie s: numbers are: Call 3ComFacts using your touch-tone telephone. International access Support from Your Network Supplier If additional assistance is required, contact your network supplier. section on how to contact 3Com. If you are unable to contact your networ k supplier, see the following Details about recent configuration changes, if applicable Support from 3Com If you are unable to receive support from your networ k supplier, office to find your authorized service provider: If you are outside the U.S. and Canada, contac t your local 3Com sales for customer service. Returning Products for Repair A product sent directly to 3Com for repair must first be assigned a To obtain an RMA number, call or fax: the senders expense. without an RMA number will be returned to the sender unopened, at A Y Page Page Page Page Page X Numerics E D C F K M L H N R S O P T U W Z V