Hopefully the following questions and answers will prove useful.  If these don't answer your question, please send your question by email to This e-mail address is being protected from spambots. You need JavaScript enabled to view it This e-mail address is being protected from spam bots, you need JavaScript enabled to view it .

We also suggest that you take a look at the list of known issues.

1. Where are the passwords and usernames?

   Please contact InterWorking Labs support ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it This e-mail address is being protected from spam bots, you need JavaScript enabled to view it ) for the usernames and passwords required to control Mini Maxwell.

2. Why are my impairment settings not having any effect?

   The most frequent reasons why a user's settings are not having any apparent effect are these:

   • The impairment was applied to the other direction.  Each of Mini Maxwell's "bands" is composed of a pair of impairment settings.  One of these settings establishes the impairments to be used on packets arriving on PORT0 and leaving via PORT1.  The other establishes the impairments to be used on packets arriving on PORT1 and leaving via PORT0.

   • The impairment was applied to a different band than the one that the packets are flowing through.  Mini Maxwell uses the user-specified filters to sort incoming packets into the various bands.  There are different impairment settings for each band.

   A useful trick for isolating these kinds of problems is to go through all of the bands, and for the PORT0 to PORT1 (uphill) and PORT1 to PORT0 (downhill) directions and set the drop probability to 100%.  This should have the effect of stopping all traffic.  Then those drop settings can be removed, one by one, until the traffic resumes.  That should give a good indication of which group of settings is affecting (and not affecting) your traffic.

3. If a packet does not match a filter what band does it go into?

   Band 5 is the catch-all band.  Packets that do not match any filters end up in Band 5.

   For this reason it is often useful to set some obvious impairment - like a large delay - on both the uphill and downhill sides of band 5 so that any packets that slip past the filter settings will be impaired in a way that is fairly easy to notice.

4. How do I use Mini Maxwell with gigabit Ethernet?

   The easiest way to do this is to use an inexpensive, consumer grade 10/100/1000 switch between Mini Maxwell and the gigabit Ethernet device.

   Mini Maxwell does not support gigabit Ethernet jumbo packets, i.e. Ethernet frames larger than 1500 bytes.

5. How do I use Mini Maxwell with wireless?

   The easiest way to do this is to attach a wireless "access point" to either Port0 (eth1) or Port1 (eth2) on Mini Maxwell.

   Some wireless base stations act as more than a mere access point - for instance many act as routers, firewalls, or network address translators.  In nearly every case you simply want to attach Mini Maxwell to the wireless base station in the same way you would attach other wired devices that need to communicate with wireless devices.  Often this means attaching Mini Maxwell to the "harmonica" of wired network ports found on many wireless stations that also include a built-in ethernet switch.

   Some wireless base station devices work under the control of a manager.  In these cases please feel free to discuss this with our support staff.

6. How do I use Mini Maxwell with fiber optic Ethernet?

   We have had good luck using external copper-to-fiber conversion boxes such as the TRENDnet TFC-1000MSC Multi-Mode Fiber Converter with SC-Type Connector which is available from many on-line sellers, such as Newegg.  Other converters will probably work.

   Note: Some types of converter may lock link-state on the copper ethernet side to an "on" state without regard whether optical link state has been achieved.

7. Can Mini Maxwell support High Definition television traffic?

   Yes.

   For 1500 byte packets Mini Maxwell can handle 100% of the line rate of a full duplex 100Megabit Ethernet, i.e. 8224 packets/second in each direction.  This is more than adequate to handle most forms of compressed HDTV traffic.

   For example, consider a compressed HDTV stream that of about 18,000,000 bits/second.  Most of these bits will be carried in full-sized packets of about 1500 bytes each.  That works out to about 1500 packets per second, well within Mini Maxwell's packet per second capacity.

8. What about tagged VLANs?

   Mini Maxwell does not support tagged VLANs.  Full sized Maxwell does.

9. When I ask for packet corruption, it appears that the number of packets being corrupted is low.  What's going on?

   A random bit offset is calculated each time the corruption mechanism decides that a packet is to be corrupted.  That offset may be anywhere in the entire Ethernet frame, not just the IP part of the packet.

   If the bit that is changed is within the source MAC address (48-bits/6-bytes) then the packet will still reach the intended target computer.

   If the receiving machine or its software is not overly zealous about checking consistency between source MAC address and source IP address, then the packet will be accepted and the change in the source MAC address may not be noticed.

   The chance that the corruption will occur within the source MAC address varies depending on the overall size of the packet.  That chance is greater for small packets and less for larger packets.  For small packets, typical of ICMP Echo (ping), which are typically 60 bytes, then the chance that the bit corruption will occur in the source MAC field can be as high as 10%.  This, in turn, means that the perceived loss of packets due to corruption is less than one would expect.

10. Can Mini Maxwell limit bandwidth?

    Yes.  Mini Maxwell uses a rate-limiting token bucket filter of the same kind that are found in many internet routing and switching devices.

    Please note that rate limitation is slightly different than emulation of a link.  Rate limitation is concerned with average traffic rates over a span of time; link emulation is concerned with things like the time to serialize the bits onto the link, the packet propagation delay, queue lengths and queue overflows, and the overhead of link level headers.  For most users the difference boils down to this: a rate limiter may sometimes allow a packet to flow through without delay if there has been a prior idle period, a link emulator recognizes that no packet, even if there had been an idle period, can escape serialization and propagation delays.

11. Can Mini Maxwell handle IEEE 802.1q tagged VLANs?

    Mini Maxwell will carry VLAN tagged frames between its to data interfaces.  However, the filters are not able to handle the fact that the tags move the IP headers four bytes deeper into the packet.  Consequently filters do not work properly on ethernet frames that have IEEE 802.1q headers.

    Nonetheless, Mini Maxwell can still be productively used on a VLAN trunk, i.e. an ethernet segment in which all the ethernet frames have IEEE 802.1q headers.  When no filters are used then the frames will all be classified into the default band, Band #5.  Impairments specified for Band 5 will be applied to these frames.  In other words, all of the frames on the trunked VLAN will be subject to the same set of impairments.  (Remembering, as always, that Mini Maxwell can have different impairments specified for each of the two directions of packet flow.)

12. When updating the Maxwell software can I use a Bluetooth serial device rather rather than a serial cable?

    Yes.  We often use a Bluetooth serial adapter - such as the IOGear GBS3001 as a way to connect to the serial port on Mini Maxwell from a computer equipped with a Bluetooth interface.

    The Bluetooth serial adapter is attached to the console port on Mini Maxwell.  The adapter should be set to be a Bluetooth slave and the bit/baud rate set to 38,400 bits/second.

13. Mini Maxwell hangs while booting - what should I do?

    We have noticed that on occasion that the kernel hangs during its boot-up sequence after emitting a line that says "PCI: Probing PCI hardware".  This may be a kernel bug.  In any event, should Mini Maxwell fail to boot properly you should turn the power off, wait a few seconds, and turn the power on again - this is usually most readily accomplished by unplugging the power connector for a few seconds.  Mini Maxwell is fully booted when all three of the front panel LEDs are lit green.

14. What do "uphill" and "downhill" mean?

    The terms "uphill" and "downhill" are shorthand words used in version 1 of Mini Maxwell to describe a direction for a flow of packets.  These terms are no longer used in more recent versions of Mini Maxwell

    Uphill packets are packets that arrive on PORT0 (LAN-A/eth2) and leave by PORT1 (LAN-B/eth1).

    Downhill packets are packets that arrive on PORT1 (LAN-B/eth1) and leave by PORT0 (LAN-A/eth2).

    An easy way to remember this is to imagine PORT0 being lower than PORT1; packets moving from the lower port to the upper port are moving uphill while those moving from the upper port to the lower port are moving downhill.

15. Why don't packets flow immediately when I plug-in the Ethernet cable?

    The bridging code in Linux takes a few seconds to initiate packet bridging after it detects the presence of Ethernet link-state (as indicated by one of the LED's on each of Mini Maxwell's network interface plugs).

16. I want to connect to the serial console but I am running Vista and there is no terminal emulator program?

    Microsoft has removed the Hyperterm program from Vista.

    You can download a free, opensource, alternative called "PuTTY".

    The PuTTY home page may be found at http://www.chiark.greenend.org.uk/~sgtatham/putty/

    The easiest way to install PuTTY is to download and run the PuTTY installer program.

    From PuTTY's "Session" menu select the "Serial" connection type.  That will allow you to enter the "Speed" (use 38400) and "Serial line".  The value for "Serial line" will vary from machine to machine but it will generally be of the form COM# where # is '1', '2', '3', '4', etc.  You may have to try these one at a time until you find the one that works.  Alternatively you may want to take a look at the Windows "Hardware Manager" (often found under the "System Information" link from "My Computer") and look under the Communications port item.

17. What is a good serial communications program to use for Linux?

    The "kermit" program is a good command line tool, but you may have to fetch it from the download site and compile it.

    A good alternative is PuTTY.  Your Linux distribution may already have it available as a package.  (For example, PuTTY is availble as one of the packets in the Fedora distribution.)  Go to the package manager of your Linux and see if it has PuTTY available.

    As is typical for serial ports you may have to search through your serial ports to find which logical name (/dev/ttyS# or /dev/ttyUSB#) is hooked to which physical DB-9 connector.

18. My computer has no serial port, what do I do?

    We have had good luck using inexpensive USB to Serial adaptors.  These cost about $10 from places such as NewEgg.