Alcatel-Lucent 7330 Product Information Manual page 86

3 — ONT and MDU general and interface technical specifications
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
Item
DS1/E1 WAN interfaces
DS1/E1 CES over Ethernet layer 2
GPON
DS1 standards
E1 standards
Synchronization
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.
The business ONT supports DS1 and E1 service connections at the subscriber
premises. The following TDM link types are supported:
•
structured (fractional) DS1 or E1
•
unstructured DS1 or E1
3-10
3-5 lists the specifications supported for the DS1/E1 interface.
Table 3-5 DS1/E1 interface specifications
CES DS1/E1
Gigabit
Ethernet
December 2010
ONT Product Information Guide Edition 01
Specification
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.
MEF-8 packetization as IETF PWE3 pseudo-wires
AT&T TR-6421; ITU-T Rec. G.703, G.704
Structured (fractional) and unstructured DS1
ITU-T Rec. G.703, G.704, G.706, G.732, G.823
Structured (fractional) and unstructured E1
Upstream: A 16.384 MHz local oscillator or a derived clock
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
A Gigabit Ethernet transmit reference clock of 125 MHz as per
IEEE 802.3
Alcatel-Lucent 7330/7302 ISAM FTTN R04.02.41
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