Cambium PTP 670 Series, Руководство пользователя

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Chapter 1: Product description TDM bridging
Page 1-43
TDM bridging
Note
PTP 670 does not support TDM bridging in the HCMP topology.
This section describes how TDM traffic (E1 or T1) may be carried over PTP 670 links.
If a NIDU is installed at each link end, the PTP 670 link supports up to eight E1 channels or up to
eight T1 channels. The link relays unstructured E1 or T1 data and provides accurate timing
transfer.
TDM description
PTP 670 Series bridges up to eight E1 or T1 telecoms circuits over a single-hop PTP 670
wireless link using the optional Network Indoor Unit (NIDU). The NIDU provides the eight TDM
interfaces on individual RJ45/RJ48 connectors, together with an Ethernet interface to the
operator’s data network and a separate Ethernet interface to the PTP 670 Series ODU. One
NIDU is required at each end of the link. It operates from a 48 V DC power supply.
TDM circuits established using the NIDUs are structure agnostic, meaning that the circuits can
bridge framed or unframed data.
The NIDUs are tightly integrated with associated ODUs providing for simple configuration,
accurate timing transfer, low and predictable latency, high efficiency, quick settling time, and a
timing-only mode that maintains timing transfer when the wireless link has insufficient
capacity to bridge the configured TDM data.
Through timing
TDM bridging in the PTP 670 series uses the “through timing” model. In other words, the clock
frequency used for transmitting TDM data is, on average, exactly the same as the clock
frequency received at the corresponding TDM port at the remote end of the link. The wander
and jitter in the transmit clock complies with applicable requirements of ITU-T G.823 and G.824
without additional external frequency references. Timing transfer is independent between
individual circuits, and between transmit and receive directions of the same circuit.
NIDUs and TDM
TDM circuits in PTP 670 span a single wireless link. To transmit TDM data across a network
segment consisting of several wireless links, use one pair of NIDUs for each wireless link, and
interconnect the TDM ports at relay sites.
The NIDU is not a general-purpose TDM multiplexer, and will not interwork with standards-
based products from other manufacturers. The NIDU does not support (and does not need to
support) internal, external or loop timing modes. The NIDU does not accept (or need) an
external frequency reference.
The NIDU is not separately managed, and it does not have an IP address. Instead, the ODU is
used to configure and monitor the associated NIDU through the standard HTTP/HTTPS, SNMP,
SMTP and syslog interfaces already used by the ODU.