Product Overview

The PacketBand-TDM-4D, TDM-4E and TDM-3MC deliver very high quality, completely transparent, E1/T1 circuits across different types of packet networks, (often referred to as TDM over IP, TDM over Ethernet, TDMoIP, CES, CESoPSN, PWE3 or pseudowire).

• Highly-accurate and stable clock recovery processes
• G.823 Synchronisation levels of accuracy achievable
• On high quality networks clock recovery as close as 10ppb can be achieved
• “Tuneable” to different network types
• Robust, reliable and professional quality
• Excellent management, statistics and diagnostics
• Various clocking options for different network types and clock recovery requirements
• Inter-works with other PacketBand family members PacketBand excels in delivering stable and accurately clocked E1/T1 “leased lines” over packet networks and benefit from Patapsco’s excellent support.

All references to the PacketBand-TDM-4D are also relevant for the TDM-4E and the TDM-3MC. The extra features on the TDM-4E and TDM-3MC are briefly identified within and in more detail in the separate documents available to download on the right of this page.

Connectivity Overview

• The PacketBand-TDM-4D (TDM-4D) supplies clock-locked clear channel or structured E1/T1 circuits over Ethernet, IP, or MPLS networks. It supports up to four E1/T1s and can be used in pairs or with other members of the PacketBand range.
• A 3-port unit (PacketBand-TDM-3MC) supporting Multicast is also available and this has applications in larger networks where clocking is critical and in some vertical markets such as broadcasting.

Interfaces

• 1, 2 or 4 port TSM over Ethernet E1/T1 versions available (user switchable between E1 and T1 in any combination)
• RJ45 120Ohm or 75Ohm (user switchable) via converter cable. Full E1/T1 or a fractional G.704
• 10/100/1GE UTP (Unshielded Twisted Pair RJ45) interface to the WAN
• A local 10/100/1GE UTP Ethernet port
• Optional SFP cage. Interfaces to a fibre network with the appropriate SFP module (not supplied)
• RJ12 management port (PacketBand is also manageable across the packet network)
• IEC connector for quality internal AC PSU (DC options available)

Clocking

• Clock recovery, accuracy and stability is key to TDM applications. This clock recovery performance must be maintained when migrating to an unclocked TDM over Ethernet packet network solution.
• Many types of equipment expect similar performance to that of traditional leased lines which are generally referenced to the G.823 Synchronous Interface mask. The PacketBand ranges are specifically designed and optimised to excel in this area and when used on high-quality networks can meet and exceed the G.823 requirements.
• The TDM over Ethernet clock recovery methods use a variety of mechanisms. These include advanced and sophisticated algorithms, even within the standard products, which allow users to “tune” the performance to match the Ethernet/IP network characteristics.

Clock Algorithms

• The TDM-4D supports three advanced algorithms as standard.
• These are designed and optimised for different network types, broadly-speaking one for high quality managed networks with low jitter (PDV) and packet loss, one for networks with lower performance characteristics and one for applications where stability is paramount but the G.823 mask is not targeted.
• Within these options are two further settings allowing tighter optimisation if required.
• This means PacketBand can be configured to extract the best possible TDM over Ethernet service for any given network.

Clock stability

• Clock frequency stability performance can exceed AT&T TR-62411, T1.403, G.824 and G.823 on quality networks for both Traffic and the much more demanding Synchronisation requirements. This is an important strength as many applications will either require very accurate synchronisation to run correctly (for example mobile backhaul), or there could be multiple clock sources within the network which all require aligning accurately to ensure error-free and reliable services.
• PacketBand alarms to DbManager should the recovered clock’s stability move outside of configured historic thresholds, giving immediate information should the clock deteriorate for any reason.

Clock Sources and Clocking

Although easy to use and configure, PacketBand offers customers a number of solutions for different clocking scenarios as briefly described below. A PacketBand advantage is not only very accurate clocking and reliability, but also the flexibility to work in different modes to suit a variety of situations and applications.

• TDM port
  Clock can be extracted from any of the attached user ports.
• Adaptive
  Using sophisticated recovery algorithms, clock can be derived from any of the in-coming packet streams from a remote “Master” PacketBand, in effect synchronising both devices to a common clock.

• Loop-Timing
  In instances where both ends of the circuit have a good quality common clock source (for example ISDN clocks into PABXs) both TDM-4Ds can be set to clock from this local source.
• Plesiosynchronous - PacketBand-TDM-4E only Plesiochronous (or plesiosynchronous) working means the TDM-4E can support multiple clocks and in different directions. This has two main applications.
  1. Where the TDM links at both ends provide clock and these clocks may be slightly different.
  2. Some locations need to receive TDM links from different devices (and/or different locations) which may have different clocks. The TDM-4E can provide different clocks on each TDM port.
     These clocking capabilities open unique opportunities to network different TDM over Ethernet clocks across packet networks and are covered in detail in the TDM-4E datasheet.
  3. Asymmetrical Working - PacketBand-TDM-4E only
     When running in G.703 unstructured mode, PacketBand-4E is able to transmit and receive packets of different sizes and for the packets to be sized down to the individual byte level.
     This configuration is used in certain types of networks, mainly wireless where a phenomenon called “beating” can be experienced. Please see the PacketBand-TDM-4E Application Overview or contact Patapsco for more information.
  4. Multicast - PacketBand-TDM-3MC only
     The PacketBand-TDM-3MC supports an innovative out-of-band clocking method via Multicast services. This has important advantages for larger Ethernet/IP networks and for some vertical markets such as broadcasting.
     Clocks can be recovered extremely accurately across very large networks yet the bulk of the traffic load (the user data) can be given a lower priority. See separate TDM-3MC Application Overview.
  5. Internal
     If no external quality clock is available, the TDM-4D can use its internal oscillator. Various oscillator options are available to deliver different levels of accuracy and stability and this is covered in the data sheet.
  6. Clock Hold-Over
     Problems in the packet network, for example a sudden increase in jitter or an interruption in packet delivery, can cause an unwanted movement in the recovered clock. To avoid this PacketBand enters a “hold-over” state, maintaining the recovered clock at the last value prior to the problem. This means the clock is always stable irrespective of issues within the network.

Oscillators

• The quality of the oscillator when recovering the clock across the packet network is very important. The receive PacketBand running “Adaptive” clocking uses a variety of different information and many calculations to ascertain how to modify its on-board oscillator’s output to match the clock of the remote or “master” end.
• It can be seen that the more stable the on-board oscillator, the more stable the TDM over Ethernet recovered clock.

PDV (Packet Delay Variation or jitter)

• The PacketBand-TDM-4D supports up to 400mseconds of PDV or jitter depending upon configuration parameters.
• This is normally far in excess of the PDV experienced on private networks and many Internet connections.
• The jitter buffer can be set in msec granularity and adjusted manually or automatically whilst the circuit is in place, overcoming ‘skew’ at start up time caused by the first packet in the buffer arriving later or earlier than average.
• The buffer re-orders out of sequence packets.
• Statistics are available to provide information on usage.

Ethernet and Packet Handling

• Support for 10/100/1GE.
• Support for “Jumbo-packets” up to 10,240 bytes in size.

Prioritisation

• TDM packets can be assigned IP Diffserv ( DSCP ) or ToS and 802.1p CoS values.
• Packetband supports full 802.1q tagging and the associated 802.1p
• CoS prioritisation levels.
• All egress packets including TDM links can be prioritised across four output queues using CoS (802.1p) or Diffserv/ToS values.

VLAN Handling

• PacketBand’s powerful and latest-generation on-board packet switch offers advanced 802.1Q VLAN facilities.

Link Aggregation Control Protocol (LACP)

• PacketBand-TDM-4E and TDM-3MC only
• This powerful feature enables two or more Ethernet ports connected between PacketBand and the network switch to be aggregated together as defined in LACP IEEE 802.3-2005. This aggregation makes it appear as if the multiple links are acting as a single high capacity circuit. Furthermore, it adds a level of redundancy with automatic rerouting

Rapid Spanning Tree Protocol (RSTP)

• PacketBand-TDM-4E and TDM-3MC only
• RSTP identifies the means to build an Ethernet network which contains physical loops between bridges. This facility enables PacketBands to be connected to more than one network switch via different circuits and to provide an automatic fallback in the case of a link failure, significantly improving network security and adding resilience.

Rate Limiting

• Individual packet ports can have the traffic capacity restricted in various ways.

Overheads

• In order to transport TDM data over the packet network, there is some overhead caused by caused by encapsulating the data inside the packet network protocol.  

The Protocol

• PacketBand supports a number of different packet network protocols. The user’s choice of a particular network will affect the overall size of packet headers

Size of Packet

• PacketBand supports a configurable packet size per Logical Link. There is a trade off between transmitting small packets at a fast rate (low latency, larger overhead due to protocol headers) and transmitting larger packets at a slower rate (bigger latency, smaller overhead).
• Typical overheads are in the 5% to 10% range.

Latency

• The total end-to-end latency experienced between two devices using PacketBands is made up of four elements:

Processing Delay

• The latency or processing delay through each PacketBand is optimised to be as low as possible. Typical processing delay is less than 1msec

Transmit Delay

• This is the time necessary to wait for sufficient incoming data to arrive from the attached device so a packet of the configured size can be built and transmitted over the network. This is typically around the 1msec range.

Jitter

• Packet networks differ in how consistently packets pass though them; some packets take more or less time than the average. PacketBand provides a synchronous clocked circuit to the attached devices and therefore has to have data ready and available for the relevant clock pulse. PacketBand buffers the fast packets so as to ensure the slow ones can arrive in time to be used.
• The amount of buffering is user-configurable and will depend upon the performance of the network. The amount of buffering needed (which equates to latency) is a result of the network, not PacketBand.

Transit Delay

• All packet networks have different average transit delays. These vary depending upon a large number of criteria, including the number of “hops” and whether satellites are involved. Please consult your network supplier.
• Summary: Between any pair of PacketBands on a terrestrial network, the most significant element contributing to latency is size of the Jitter Buffer (which is user configurable). This is directly dependant on the performance of the network and outside the control of PacketBand.

CESoP Modes

• PacketBand supports both “Structure Aware” and “Structure Agnostic” TDM over Ethernet/IP modes.
• Complies with ITU-T recommendation Y.1413, IETF PWE3 draft standards CESoPSN, SAToP and CES draft IAs from MEF and MFA.

Approvals

• All approvals completed in a UK Accredited laboratory. Reports available. CE marked.
• Safety and Emissions ( EMC ) approvals (CE and FCC).
• Telecoms approvals for connection to carrier leased lines is optionally available.
• PacketBand TDM-4D is RoHS compliant

Management

• PacketBand can be locally or remotely configured using Patapsco’s easy-to-use high functionality DbManager GUI software.

• DbLite is supplied free with each unit. Optionally available are different versions to support requirements for larger or more integrated networks. It is sophisticated but simple to use via an intuitive Graphical User Interface (GUI) which
• controls, configures and monitors individual Patapsco units. It can generate SNMP Traps and Alarms.
• A document identifying the differences between DbLite and other versions is downloadable.
• The status of all PacketBands and links are easy to identify with Alarms being colour coded and passed up the tree. Separate windows provide Event and Alarm information with the ability for operators to add comments etc. Different access levels and passwords provide operators with appropriate capabilities within the program.
• An option to encrypt the management traffic across the packet network is available, together with key management/update system.
• More information is available in the downloadable PDFs.

PacketBand is a quality, flexible professional TDM over Ethernet/IP product with many important features and capabilities - yet at a very competitive price. Designed, manufactured and supported by Patapsco – a company of 20 years standing.

Further details and specifications are available in the PDFs at the Top of this page and when registered.