PacketBand-ISDN General FAQs -Please see here for technical FAQs

Q1.What is ISDN over IP or ISDN over Ethernet?

Q2. How does PacketBand differ from a VoIP unit with ISDN ports?

Q3. When would I use PacketBand?

Q4. What type of BRI/PRI port do I need?

Q5. Can I break in/out of the PSTN public ISDN?

Q6. What type of devices can I attach to a PacketBand-ISDN?

Q7. What is the SIP Server option for?

Q8. Can I just plug my PacketBand-ISDN into somewhere like a hotel Internet port and access other devices?

Q9. Why do I need PacketBand-ISDNs at both “sides” of the packet network?

Q10. How is PacketBand different from a VoIP solution?

Q11. Can I run ISDN video across PacketBand-ISDNs?

Q12. Can I use PacketBand-ISDN to extend ISDN from my comms room to another location on my LAN/WAN?

Q13. Can multiple ISDN users share the PSTN/ISDN network ports?

Q14. Can I route in-coming ISDN calls from the network to specific ISDN ports?

Q15. What is a Logical Link?

Q16. Can I use PacketBand on the public Internet and what are the issues?

Q17. Which PacketBands can inter-work?

Q18. Can I use a satellite link?

Q19. Will the link carry any traffic transparently?

Q20. What is a Lost packet and a Late packet?

Q21. Does PacketBand support VLAN Tagging?

Q22. Does PacketBand support quality of service options?

Q23. Does the PacketBand support NAT Traversal?

Q24. What are the extra Ethernet ports for?

Q25. What is the latency added by PacketBand?

Q26. Why do I need a PacketBand at both ends of the circuit?

Q27. How much bandwidth will my PacketBand occupy?

Q28. How do I know where the clocking will come from for the system?

Q29. There are firewalls on the sites where PacketBand will be used. Will it still work?

Q1. What is ISDN over IP or ISDN over Ethernet?

When you use a carrier’s ISDN network the calls are in effect connected together on point-to-point circuits. The calls are transparent (you can send any kind of traffic voice or data) and they are clocked or synchronised.

A packet network has very different characteristics. As the name says it is packet-based, all traffic goes over common cables and importantly there are no clocks. In addition, the ISDN network delivers data at a steady pre-defined rate whereas a packet network has "jitter".

The PacketBand, uniquely, over-comes all of these issues to turn a packet network into a virtual ISDN network. Any data can be transported. Calls can, if wished, be completely dynamic and be placed between any location, cleared and another site dialled. Clocks are synchronised so all interfaces are clock-locked, even when calls are cleared and remade to different sites.

Ideal for all applications, particularly synchronous applications like videoconferencing, codecs, encryptors but also useful for faxes and modems. Plus it gives great PCM toll-quality very low-latency voice connections.

In fact it performs just like the traditional carrier-delivered ISDN but using low-cost packet networks.
PacketBands connected to the packet network and the ISDN PSTN provide users with break-out ability so they can still call anyone anywhere in the world as well as be called.

A great migration tool for carriers and corporates alike. Back to top

Q2. How does PacketBand differ from a VoIP unit with ISDN ports?

VoIP equipment do what they say; "Voice over IP". They convert voice to packets and transport this data across a network and then de-packetise it at the other end. they also generally compress the traffic.

The differences between a VoIP solution and PacketBand are many. The most significant ones are:
A VoIP unit can communicate across the public Internet to any other VoIP phone; the PacketBand is a 2-ended solution that resides at the edges of private networks (although it does also work across the Internet between two PacketBands).

A VoIP system is not clocked so calls between devices are not synchronised or locked. This causes data loss which is not necessarily so important for voice (although we have all experienced poor voice calls over VoIP), but it is critical for many data applications.

PacketBands are synchronised and there is no loss of voice/data because of clock slips or incompatibilities. For example videoconference calls using multiple BRI ports can be placed across packet networks and then break-out into the PSTN.

PacketBands will transport any type of traffic.

PacketBands also transport signaling end-to-end and by way of an example, supports UUS-3 (User to User Signaling).
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Q3. When would I use PacketBand?

Typically in the following scenarios:

Where you need to transport synchronous data traffic across a packet network. This includes video, encryptors, codecs, faxes and modem traffic.

Where you have control over the end-points, such as in a private network or across the Internet between known destinations.

Where you need excellent quality voice with low latency and no clock slips/hits.

Where you have traditional PBXs and want to use your corporate packet network for high quality voice and other non-voice applications.

Where you need to migrate customers from a traditional ISDN network to a packet network and you have no control over what they connect. Plus where you do not want the Technical support problems associated with a migration which is CPE dependant.

Where you need to extend ISDN services across a LAN or WAN.

Where ISDN cabling and distances cause you problems and costs and you would rather just plug your ISDN traffic, such as videoconferencing units, into your structured cabling.

PacketBand also has extremely flexible routing, resiliency and number manipulation capabilities and special security features.

You will be surprised at the PacketBand's abilities and the number of ways it can be implemented and used. Call us to discuss your ideas and applications. Back to top

Q4. What type of BRI/PRI port do I need?

All Patapsco ISDN products work under the same principal, if you require your BRI/PRI ports to connect to a network connection (for example BT’s ISDN2 or ISDN30) you will need “TE” (for connection to the Network) ports.

If you require your Patapsco device to connect to a piece of terminal equipment (for example PBX, Video conference unit, IVR etc) you will need “NT” (for connection to Terminal Equipment).
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Q5. Can I break in/out of the PSTN public ISDN?

PacketBand may be fitted with TE interface PRI or BRI ports, which may be connected to ISDN lines to interface with the PSTN. PacketBand can route calls out to/in from the PSTN based on DDI, CLI, Subaddress, port, channel number and call type. PacketBand will take clock from the network interface which it will use to clock all of its transmissions. Back to top

Q6. What type of devices can I attach to a PacketBand-ISDN?

Any Euro-ISDN E1 PRI or NET3 BRI device will work with PacketBand. Typically these devices include Phones, Faxes, Routers, PABXs, Video Conferencing units, Codecs, Secure/encryption devices and IVRs. Back to top

Q7. What is the SIP Server option for?

The call routing for a PacketBand system can be centralized using a SIP server unit. PacketBands route all of their call traffic to the SIP server and the SIP server has routing profiles configured to handle the traffic and route to the correct destination. A Patapsco ‘SIP Manager’ application is available for configuring a SIP server. Please contact Patapsco for more information. Back to top

Q8. Can I just plug my PacketBand-ISDN into somewhere like a hotel Internet port and access other devices?

PacketBand uses SIP messages to set up calls, which must be NAT translated through routers out to the public internet. This requires that the public IP address of the router is known and configured in the NAT settings of PacketBand. Any firewalls must also be configured to allow incoming connections. In hotels and other places with public internet access, IP address details and firewall settings are not always accessible. In this case, PacketBand can be configured to use TCP for the call signaling messages rather than UDP. The TCP protocol has a ‘tunneling’ effect which means that the firewall ports do not have to be explicitly opened for call setup responses, and the NAT settings do not need to be configured, so the public IP address does not need to be known. This system will usually only work in one direction; for example from a hotel to a ‘master’ site which has a static IP address and the necessary firewall ports open. Back to top

Q9. Why do I need PacketBand-ISDNs at both “sides” of the packet network?

PacketBand is not able to ‘convert’ TDM data or ISDN data into a usable Ethernet packet. The PacketBand system encapsulates the data so that it can be passed across a packet switched network. When the packet arrives at the destination site, it must be un encapsulated by another PacketBand unit before it can be used by a synchronous TDM or ISDN device. The packet is not suitable for use with another Ethernet device. Back to top

Q10. How is PacketBand different from a VoIP solution?

VoIP is a lossy voice compression protocol, which does not attempt to address the issues surrounding running a synchronous application (voice communication) across an asynchronous network. VoIP applications are sometimes of a poor quality and may be interrupted by regular packet loss.

PacketBand ISDN however, is able to maintain the level of quality associated with synchronous ISDN communications; adjusting dynamically to network conditions and maintaining high quality communications as conditions change. PacketBand ISDN is also able to carry ISDN data and video transmissions, as well as encrypted data. In fact, any ISDN application can be moved to a PacketBand ISDN system. The only factor which must be reasonably stable is the quality of the packet switched network. Back to top

Q11. Can I run ISDN video across PacketBand-ISDNs?

Yes. PacketBand ISDN has full support for BRI and PRI video conferencing systems. Back to top

Q12. Can I use PacketBand-ISDN to extend ISDN from my comms room to another location on my LAN/WAN?

Yes. This is no problem for PacketBand ISDN. As well as extending an ISDN connection to another location, PacketBand could change the presentation from PRI to BRI or vice versa. Back to top

Q13. Can multiple ISDN users share the PSTN/ISDN network ports?

PacketBand has support for multipoint connections on BRI ports. This means that up to eight users could connect to the S-Bus on a single BRI port. Also, PacketBand ISDN can be fitted with up to eight BRI ports or four PRI ports. These ports can be distributed between a group of devices, and calls can be routed to and from each port based on the on DDI, CLI, Subaddress, port, channel number and call type. Back to top

Q14. Can I route in-coming ISDN calls from the network to specific ISDN ports?

Yes. PacketBand has a comprehensive suite of call routing functions, allowing routing based on DDI, CLI, Subaddress, port, channel number and call type. Secondary and tertiary destinations for calls can also be configured, so as to have backup destinations for calls in the event that the primary destination is busy. ‘Hunt groups’ of ports or channels can also be configured for group sources or destinations. Schedules for routing profiles are available, so different routing profiles with different settings can be enabled or disabled at different times of day. Back to top

Q15. 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 "B" channels 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).
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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. Which PacketBands can inter-work?

Any PacketBand-ISDN units inter-work. Any "B" channel can establish a call to any other, irrespective of the type of ISDN (BRI or PRI, E1 ETSI or T1 ANSI). ISDN versions of PacketBand can also connect to TDM versions, so a BRI PacketBand, for example, could establish a call to a V.35 TDM unit - call us to discuss. Back to top

Q18. 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 delay is reasonably stable. Back to top

Q19. Will the link carry any traffic transparently?

Yes, PacketBand ISDN delivers a clear channel for use by any traffic. Back to top

Q20. 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 variable 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

Q21. Does PacketBand support VLAN Tagging?

Yes Back to top

Q22. Does PacketBand support quality of service options?

Yes Back to top

Q23. Does the PacketBand support NAT Traversal?

Yes Back to top

Q24. 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 PacketBand's transmissions.

A useful feature of having spare Ethernet ports is the ability to configure one as a 'sniffer' port. This port can have a PC connected running packet monitoring software. All activity on the port connected to the PSN is mirrored to the sniffer port, making this a very useful when debugging.

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

Q25. 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

Q26. Why do I need a PacketBand at both ends of the circuit?

The PacketBand system encapsulates the data so that it can be passed across a packet switched network. When the packet arrives at the destination site it must be un encapsulated by another PacketBand unit before it can be used. The packet is not suitable for use with another Ethernet device.

It is also vital for ISDN traffic that it is delivered in the correct order, when expected and that the two ends of the ISDN circuit are clock-locked and synchronised together.

PacketBand-ISDN also handles signaling conversion between BRI and PRI and E1 and T1. Back to top

Q27. 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 and potentially better clocking.

A typical bandwidth requirement for a single 64kbps "B" channel between two destinations is around 120kbps (this can be reduced down to around 80kbps for satellite applications). But multiple ISDN "B" channels between the same two end points are "wrapped" into the same Logical Link so only need extra blocks of 64kbps, so in the situation above 1xB is 120kbps; 2xB is 184kbps; 4xB is 312Kbps etc.

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

Q28. 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). PacketBand-ISDN performs a number of "invisible" tasks to ensure the clocks are synchronised and recovered across the network, including negotiating with any connected peers to determine who has the best source or who has a network clock, and renegotiating this as calls are made/cleared between different devices. This process is automatic, not seen by the user, who does not experience any change or degradation in service whist this is happening. 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 port numbers:

The Logical Link port numbers can be changed. Please see the PacketBand manual for details.
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Should you be unable to find the answer you seek, or are having difficulties, please contact us referencing any Support Agreement.