PacketBand-TDM Technical FAQs - For additional help please see our Movie.
All TDM Versions:
- Q. Where can I download the DbManager software?
- Q. Where can I find cable specifications?
- Q. Where can I find the manual?
- Q. How do I connect to the device?
- Q. What does NT mean?
- Q. What does TE mean?
- Q. What do Patapsco’s different coloured cables mean?
- Q. I can’t see some of the settings shown in the manual/they are grayed out. Why?
- Q. When I upload to my device, I get an error message about commands not being accepted. Why?
- Q. I am using an old version of DbManager. How can I upgrade?
- Q. I only have one device node to connect to my units. How can I add more?
- Q. How do I save the configuration to the device?
- Q. What PacketBands can inter-work?
- Q. What is a Logical Link?
- Q. What are the best Frames Per Packet settings to use?
- Q. Can I use PacketBand on the public Internet and what are the issues?
- Q. Can I use a satellite link?
- Q. Will the link carry any traffic transparently, even signaling protocols like DPNSS and QSIG?
- Q. What is a Lost packet and a Late packet?
- Q. Does PacketBand support VLAN Tagging?
- Q. Does PacketBand support quality of service options?
- Q. What are the extra Ethernet ports for?
- Q. What is the latency added by PacketBand?
- Q. My PacketBands only have 1 Logical Link and I need more. How can I add more Logical Links?
- Q. How much bandwidth will my PacketBand occupy?
- Q. How do I know the best Jitter Buffer setting to use?
- Q. How do I know where the clocking will come from for the system?
- Q. I'm seeing a lot of packet loss on my link. What can I do about it?
- Q. There are firewalls on the sites where PacketBand will be used. Can it still work?
- Q. Should I use G.703 or G.704?
- Q. I have an application with two separate clock sources. Can PacketBand cope with this?
- Q. I already have the same clock source at both locations, so I don't need clock recovery. Is this OK?
Packetband-V11/V35 Only
- Q. I only want capacity a certain times, how can I do that?
- Q. What is "Control Signal Dialling "?
- Q. What speeds do the X.21 and V.35 versions run at?
- Q. Can the V.35 and X.21 PacketBand communicate with E1 PacketBands ?
Q1. Where can I download the DbManager software?
Please register at http://www.Patapsco.co.uk/Top_Level/LogIn_Register.asp for access to DbManager software. Back to top
Q2. Where can I find cable specifications?
All cable specifications can be located in any Patapsco manual. Back to top
Q3. Where can I find the manual?
All Patapsco product manuals and quick start guides can be located on the CD provided. They can also be found by signing in to www.patapsco.co.uk. Back to top
Q4. How do I connect to the device?
PacketBand can be initially connected to via the serial cable provided with the unit. Alternatively, the default IP address can be used for IP connection to the unit. Once a connection has been established with PacketBand, a new IP Address can be configured. All Patapsco devices have a default IP address of 192.168.0.1 Back to top
Q5. What does NT mean?
The NT ports on a Patapsco device present as a Network, i.e. for connection to a piece of Terminal (TE) equipment. Back to top
Q6. What does TE mean?
The TE ports on a Patapsco device present as a Terminal or User port, i.e. for connection to a Network (NT). Back to top
Q7. What do Patapsco’s different coloured cables mean?
Green = E1/T1/PRI, BRI and Ethernet straight
Yellow = PRI crossover
Red = BRI crossover Back to top
Q8. I can’t see some of the settings shown in the manual/they are grayed out. Why?
DbManager can be configured to run in two modes; Starter and Expert. Starter grays out or removes some of the more advanced options within DbManager, while Expert mode shows all available options. The mode can be switched by going to View - Properties - Device Configuring. Back to top
Q9. When I upload to my device, I get an error message about commands not being accepted. Why?
If commands are not accepted on an upload, the most likely cause is that the version of DbManager in use is older than the firmware on the Patapsco unit. If you have a DbManager installation disk, please see the ‘Upgrade’ folder for information on how to upgrade, or contact Patapsco for instructions on how to upgrade. Back to top
Q10. I am using an old version of DbManager. How can I upgrade?
If you have a DbManager installation disk, please see the ‘Upgrade’ folder for information on how to update, or contact Patapsco for instructions on how to upgrade. Back to top
Q11. I only have one device node to connect to my units. How can I add more?
DbManager Lite only allows a single node to be configured for use. Once IP addresses are added to the IP list, the node can be configured to connect to each configured address as required. IP addresses can be configured in View - Properties - Terminal - Device IP Addresses, and the node can be reconfigured by right-clicking it (Ctrl + right-click for older DbManager versions) and going to Properties - IP List. Please contact Patapsco if multiple nodes are required. Back to top
Q12. How do I save the configuration to the device?
All configuration changes must be uploaded to the device when finished. Changes to the configuration are made ‘offline’, and only take effect when uploaded. Go to File - Upload to load the changes to the device. Config files can be saved to disk by going to File - Save File, and loaded to devices by selecting ‘Load File’ followed by ‘Upload’. Back to top
Q13. Which PacketBands can inter-work?
Generally, any PacketBand TDM family device will work with any other. Some have features not supported on others but all have the same core/base feature set and can inter-work. Back to top
Contact patapsco if you need further information
Q14. What is a Logical Link?
A Logical Link is a connection between two PacketBand units across a packet switched network. A single Logical Link can support up to 32 TDM channels (timeslots) between these two units. If a unit has one timeslot going to each of two PacketBands it will require 2 Logical Links. Each Logical Link can be configured with different settings (QoS and VLAN tags for example). Logical Links are sometimes referred to as Switched Virtual Circuits (SVCs). Back to top
Q15. What are the best Frames Per Packet settings to use?
The default value is 20, which is a good place to start unless bandwidth allocation is an issue. Generally speaking, the Frames per Packet value should be as low as possible where bandwidth will allow as this tends to deliver the best clock recovery. If the packet switched network is known to have an amount of packet loss, then a lower frames per packet value should be used so that a lost packet will not cause so much data to be lost. Please see the PacketBand Overhead Calculator to work out how much bandwidth a system will occupy. This can be found on the DbManager installation disk. Back to top
Q16. Can I use PacketBand on the public Internet and what are the issues?
PacketBand can be used on the public Internet, provided there is enough network capacity available (remember an ADSL link will have a slow direction which is the limiting capacity of the link and there may also be considerable contention).
PacketBand has no control over packet loss across the link and packet loss means lost data.
The unpredictable nature of the public Internet and lack of prioritisation and management can make stable, synchronous communications systems difficult to run. Having said that, Patapsco does have some good experience in running services across the Internet.
Some actions can be taken to maximise the service and these include using the same ISP at each end of the circuit and using an ISP with QoS (Quality of Service) offerings.
National links and links within a region such as Europe will perform better than long distance inter-continental/regional links. Back to top
Q17. Can I use a satellite link?
PacketBand has been proven to work on many satellite links with excellent results. The large amount of extra delay associated with satellite transmissions is no issue for PacketBand, provided the PDV is reasonably stable. Back to top
Q18. Will the link carry any traffic transparently, even signaling protocols like DPNSS and QSIG?
PacketBand TDM will handle all protocol types transparently, simply passing the data to the end devices unchanged. This will work the same way in both G.703 (unstructured) and G.704 (structured or framed) modes, except that timeslot 0 is not passed on G.704 connections, but reconstituted locally.
Reconstituting timeslot 0 has some significant advantages when inter-connecting E1 devices on a network with packet loss. If running G.703 and packets are lost, the E1 interface of the attached devices may shut down after a number of lost timeslot 0 packets. When running G.704 mode this will not happen as the timeslot information is generated locally. Back to top
Q19. What is a Lost packet and a Late packet?
PacketBand uses a buffer to collect and reorganize packets as they arrive from the packet switched network. The buffer can be configured to a defined size in order to catch the disorganized and transit delayed packets, without adding an unnecessary amount of extra latency to the system in processing time.
Early and Late packets are packets which arrive outside the range of the Jitter Buffer due to being very late or very early (these are rare) in crossing the packet switched network.
Lost packets are gaps in the packet sequence numbers, indicating that the packet was never received, and so was lost within the packet switched network. Early, Late and Lost packets are all unusable by PacketBand and the attached device and therefore are counted as Underruns. Back to top
Q20. Does PacketBand support VLAN Tagging?
Yes . VLAN tags can be added on a per-Logical Link basis, and PacketBand's onboard Ethernet switch can be configured to add and remove VLAN tags for passing traffic, as well as prioritise traffic based on its VLAN tag. Back to top
Q21. Does PacketBand support quality of service options?
Yes. Type of Service settings for Delay, Throughput, Reliability, Cost and Precedence can be entered, or a DiffServ Codepoint value can be manually entered, which will be used for Logical Link traffic. Back to top
Q22. What are the extra Ethernet ports for?
The extra Ethernet ports on PacketBand allow other Ethernet devices access to the packet switched network via PacketBand's onboard Ethernet switch. These ports can then be Rate Limited or the traffic prioritised so as not to interfere with the TDM packets.
Another useful feature of having spare Ethernet ports is the ability to configure a spare port as a 'sniffer' port. This port can have a PC running packet monitoring software running connected, and all activity on the port connected to the PSN is mirrored to the sniffer port. This can be very useful when debugging a system.
LACP (Link Aggregation Control Protocol) can use more than one Ethernet port to aggregate more than one network circuit together for extra capacity, load-sharing and resilience. Not all PacketBands support this option.
RSTP (Rapid Spanning Tree Protocol) both protects Ethernet networks from loops (or "short circuits") and can also be used to provide a "hot-standby" network link for resilience. Not all PacketBands support this feature. Back to top
Q23. What is the latency added by PacketBand?
The main setting to take into account when considering the latency added by PacketBand is the length of the Jitter Buffer. The Jitter Buffer should be configured large enough that it will catch early and late packets, but not so large that an inordinate amount of latency is added to the system and not used. Please see the PacketBand manual for a full description of the Jitter Buffer settings. Some of the other Logical Link settings will affect the amount of extra latency imposed by PacketBand, and these are also explained in the manual. Back to top
Q24. My PacketBands only have 1 Logical Link and I need more. How can I add more Logical Links?
Logical Links can be usually added to an existing unit using a configuration number supplied by Patapsco. Please contact Patapsco to purchase extra Logical Links and see the Ordering Information documents. Back to top
Q25. How much bandwidth will my PacketBand occupy?
The bandwidth allocation of a PacketBand system is based on many factors. As a general guide, setting a higher Frames per Packet value will generate less bandwidth overhead because there is less Ethernet/IP overhead for any given payload.
However, large or infrequent delivery of packets will impact negatively on the clock recovery processes.
Conversely, a low Frames per Packet value will require higher bandwidth but reap potentially better clocking.
It should be noted that when running at higher speeds (full T1/E1 for example) the change in Frames per Packet does not have a very large impact on overheads; it is at the low speeds that it is more noticeable.
The full user manual for PacketBand explains the settings which affect bandwidth, and the PacketBand Overhead Calculator can be used to work out how much bandwidth a system will occupy. Both of these resources can be found on the DbManager installation disk and by Registering. Back to top
Q26. How do I know the best Jitter Buffer setting to use?
Jitter is the variation in delay time across a packet switched network. It is sometimes referred to as Packet Delay Variation (PDV). A high quality, managed packet switched network will often have a defined or maximum amount of jitter. Please consult a network administrator and ask about jitter.
If the amount of Jitter is not already predetermined, it is possible to monitor the Jitter on the network using PacketBand. PacketBand monitors its Jitter Buffer, and will report when packets fall outside the Jitter Buffer range. These are reported as Late and Early packets, and indicate that the Jitter Buffer length should be extended. Graphs of Jitter Buffer usage are also available on DbManager and alarms can be generated if the network starts to perform outside of a configured threshold.
Please see the PacketBand TDM manual for more information or contact Patapsco. Back to top
Q27. How do I know where the clocking will come from for the system?
Correct clocking for a system is absolutely vital - without it you will experience lost data (at best). Most PacketBands must have a single clock source (unless running Plesiochronous clocks) and this can be from a variety of possible sources depending upon the unit. Please consult the full PacketBand manual for details on PacketBand's clocking requirements. Back to top
Q28. I'm seeing a lot of packet loss on my link. What can I do about it?
Packet loss can be experienced on poor quality and/or heavily loaded packet switched networks. PacketBand has no control over packet loss. The connection can be improved if PacketBand traffic can be prioritised over other traffic on the network. PacketBand supports QoS, ToS, VLAN, Diffserv and VPN. There are some other factors which can cause packet loss:
1. Half duplex links - PacketBand must have a full duplex path to other PacketBand devices. Switches and Routers connected to the system should be set to auto-negotiate or fixed to full duplex. If they are not you may see periodic and quite regular packet loss as a result of collisions.
2. Protocol Type - Please check that PacketBand is set for the correct protocol type for the packet switched network.
PacketBand can be configured with a sniffer port, which can be used with packet tracing software to prove that packets are being lost within the network. Please contact Patapsco for more information.
Back to top
Q29. There are firewalls on the sites where PacketBand will be used. Will it still work?
Yes, PacketBand can be used provided the correct port numbers are opened on the firewall and port forwarded to the PacketBand. PacketBand uses the following default port numbers:
Port Number |
Protocol |
Function |
3001 |
TCP |
Management traffic |
49152-49215 |
TCP+UDP |
Logical Links 101-164 |
The Logical Link port numbers can be changed. Please see the PacketBand manual for details. Back to top
Q30. Should I use G.703 or G.704?
Patapsco recommends G.704 wherever possible. G.703 should only be used if it is absolutely necessary to pass timeslot 0 across the link. G.704 mode reconstitutes timeslot 0 locally so that it does not need to be passed across the link. This is very beneficial in the event of packet loss as the framing channel (0) will not be affected, which would otherwise cause the connected TDM device to reset the connection. Please see the PacketBand TDM manual for more information. Back to top
Q31. I have an application with two separate clock sources. Can PacketBand cope with this?
PacketBand TDM has versions with support for a PDH (Plesiochronous Digital Hierarchy) environment. This Plesiochronous or Plesiosynchronous mode allows networks with separate clock architecture to interconnect via a PacketBand system. This method sends the transmit clock from each CPE across the PacketBand system, using each CPE's clock for the transmitted data.
Plesiochronous clocking is covered in more detail in the appropriate model's brochure and manual. See the PacketBand-TDM Product Comparison sheet for a summary of features. Back to top
Q32. I already have the same clock source at both locations, so I don't need clock recovery. Is this OK?
Yes. PacketBand TDM can be configured in Loop Timing mode. Loop Timing allows PacketBand to loop the Tx and Rx clocks from a CPE back on themselves. The clock is not passed across the IP network, so no clock recovery takes place. This option should be used when both CPEs have the same clock source, so no clock recovery is required and PacketBand provides the packetisation and depacketisation and uses its jitter buffers to "smooth" the traffic compensating for fast/slow packets. Back to top
TDM/V35/V11 only.
Q1. I only want capacity a certain times, how can I do that?
A schedule can be set for each Logical Link, so that it is only enabled within defined periods . If the link is only needed when calls are made between two end user devices, it may be worth considering the PacketBand ISDN product range instead, which supports fully switched, dynamic call handling for BRI and PRI. Back to top
Back to V11/V35 questions
Q2. What is "Control Signal Dialling "?
PacketBand VX has the ability to monitor its serial interface for control signals and to then establish the TDM link across the packet network in response, thus instead of a permanent 24/7 circuit in place, it is "on-demand".
The control signal which will trigger this is 'C' for X.21 units and 'DTR' for V.35 units.
If you would like more information please contact Patapsco. Back to top
Back to V11/V35 questions
Q3. What speeds do the X.21 and V.35 versions run?
PacketBand VX can be configured to run at any speed from 64kbps to 2048kbps in steps of 64kbps.
Back to top
Back to V11/V35 questions
Q4. Can the V.35 and X.21 PacketBand communicate with E1 PacketBands ?
Yes, PacketBand VX can fully interwork with E1/T1 PacketBand units.
When running at less than a full E1/T1 the E1/T1 PacketBand must use its channelised or framed option so each 64kbps step on the PacketBand VX represents one timeslot or channel on the PacketBand TDM unit.
If running a full 2.048Mbps the PacketBand E1 can run unstructured G.703 or if at 1.544Mbps a full unframed T1. Back to top
Back to V11/V35 questions
Should you be unable to find the answer you seek, or are having difficulties, please contact us referencing any Support Agreement.
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