3 — ONT and MDU general and interface technical specifications
3-12 November 2013 Alcatel-Lucent 7302 ISAM | 7330 ISAM FTTN | 7360 ISAM FX ONT R04.06.02
Edition 01 3FE 55873 AAAA TCZZA
ONT Product Information Guide
Structured DS1 or E1 services emulate fractional services where the 1.544 Mb/s
DS1, or 2.048 Mb/s E1, bandwidth is subdivided in to DS0 64 kb/s channels.
Framing is used to group together multiple DS0s when the service is structured or
fractional. Unstructured services treat the full bandwidth of a DS1 or E1 link as
though it were one large channel, ignoring any framing.
CES encapsulation is a method of carrying TDM traffic in an Ethernet frame so that
there is minimal loss of quality. The ISAM performs CES on the TDM traffic
received at the ONT DS1 or E1 port using the MEF-8 payload structure for transport
as Ethernet layer 2 packets over pseudo-wires (PW). The TDM payload within the
MEF-8 packet, whether it is structured or unstructured, is treated as a bit stream. The
MEF-8 packets are multiplexed along with other Ethernet layer 2 data packets at the
ONT before being transported across the GPON.
In unstructured mode, the payload size is fixed at eight DS0 frames per MEF-8
packet. For DS1, the payload length is fixed at 192 bytes per frame. For E1, the
payload length is fixed at 256 bytes per frame. In structured mode, the payload length
is determined from the encapsulation delay setting.
Table 3-6 lists the specifications supported for the DS1/E1 interface.
Table 3-6 DS1/E1 interface specifications
Note
(1)
The upstream derived clock that is provided by the P-OLT is tied to the BIT clock and must be
traceable to a network timing reference. The derived clock is used for differential clock recovery
and for timing the upstream PWE3 packet streams in the absence of a valid TDM recovery clock.
CES Overview
Circuit Emulation Services (CES) encapsulation is supported on DS1 and E1 TDM
traffic for transport as Ethernet layer 2 over the GPON using the Metro Ethernet
Forum standard MEF-8 payload structure and pseudo-wire (PW) technology. CES
and the DS1 or E1 ports may be provisioned on the business ONT using a TL1 or an
EMS management session with the P-OLT.
Item Specification
DS1/E1 WAN interfaces Two RJ-48C ports configured for 100 Ω DS1, 120 Ω balanced E1,
or 75 Ω unbalanced E1. An external adapter is required for 75 Ω.
DS1/E1 CES over Ethernet layer 2
GPON
MEF-8 packetization as IETF PWE3 pseudo-wires
DS1 standards AT&T TR-6421; ITU-T Rec. G.703, G.704
Structured (fractional) and unstructured DS1
E1 standards ITU-T Rec. G.703, G.704, G.706, G.732, G.823
Structured (fractional) and unstructured E1
Synchronization CES DS1/E1 Upstream: A 16.384 MHz local oscillator or a derived clock
(1)
from the GPON that is provided by the P-OLT
Downstream: Either a 16.384 MHz adaptive clock received from
the PWE3 packet stream or a differential clock recovered from
the PWE3 packet stream
Gigabit
Ethernet
A Gigabit Ethernet transmit reference clock of 125 MHz as per
IEEE 802.3
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