Zhone Technologies ZTI-PG - Manual (Page 6)

 Z H O N E T E C H N O L O G I E S E T H E R N E T O V E R C O P P E R
specification, coming out of the work of the Metro
Ethernet Forum, is used primarily for core and distribu-
tion network services over fiber and is not relevant to
SMO and cell site target segments under consideration
here. The last category, Pre-Standard Ethernet over
Copper, refers to the proprietary technology for Ethernet
on bonded copper loops that was originally developed by
a small company named Net to Net in the late 1990s and
acquired by Zhone in 2005. A number of Zhone custom-
ers continue to use this technology quite successfully.
One other term with some currency in the industry is
“carrier Ethernet” — used variously as an umbrella term
to refer to the services that operators can offer with any
of these technologies, or sometimes more specifically to
refer to Ethernet services in the core or distribution
networks. Our focus for the balance of this discussion is
on EFM over Copper, which in practice is usually short-
ened to just EFM.
How EFM Works
In simplest form, EFM is a straightforward combination
of packet data in Ethernet frames carried over an SHDSL
physical layer on one or more last-mile twisted pair
copper loops. An EFM connection is made between an
Ethernet access device (EAD) at the customer premise
and typically an EFM aggregation platform in the central
office, or in some cases directly with an EAD at another
premise. EADs deliver WAN connectivity on the premise
through an Ethernet port to a standalone device or a
LAN switch, and they may also provide emulated legacy
interfaces (POTS, T1/E1) as well.
The IEEE 802.3ah standard incorporates a number of
advances in Ethernet over last-mile twisted pair, includ-
ing:
• use of the SHDSL physical layer for high symmetric
data rates per twisted pair (up to 15 Mbps)
• direct connection between the Ethernet MAC layer and
the SHDSL PHY layer, avoiding latency and frame
overhead associated with prior approaches that
retained ATM encapsulation and adaptation in the
process
• support for multiple twisted pairs in a bond group that
are combined to form one virtual Ethernet connection
with higher speeds and resiliency — as shown in the
diagram on the facing page, individual inbound
Ethernet frames are divided by EFM devices into
fragments optimized for current loop performance
before being sent in parallel over the bond group, one
fragment to a pair, and then re-assembled on the
receiving end.
Choices for Ethernet in the Access Network
T1, E1, SHDSL.bis SHDSL.bis 10/100/1000 Base T 1000/10000 Base T Physical
Layer
None
(Net-to-Net protocol)
IEEE 802.3ah EFM IEEE 802.3ah EFM MEF* 10 Technical
Specification
Standard
Pre-Standard
Ethernet over Copper
EFM over Copper Active Ethernet Metro Ethernet Category
SME
(inc. T1/E1 or frame
relay replacement)
SME
(inc. T1/E1 or frame
relay replacement)
Small/medium
enterprises (SME)
Residential triple play
Large enterprises Target
Segments
Unlimited for T1/E1;
< 7 km / 4.5 mi. for
SHDSL.bis
Up to 7 km (4.5 mi.) 10–40 km (6–25 mi.)
depending on optics
10–40 km (6–25 mi.)
depending on optics
Reach
1.5–5.7 max Mbps
per pair (to 45 total)
Up to 5.7 Mbps per
pair (max 45 Mbps)
10/100/1000 Mbps 1–10 Gbps Data
Rates
Point to point Point to point Point to point Ring, star Topology
1 to 8 voice-grade
Cat-3 copper pairs
1 to 8 voice-grade
Cat-3 copper pairs
1 single-mode optical
fiber
1 single-mode optical
fiber with WDM
Physical
Medium
T1, E1, SHDSL.bis SHDSL.bis 10/100/1000 Base T 1000/10000 Base T Physical
Layer
None
(Net-to-Net protocol)
IEEE 802.3ah EFM IEEE 802.3ah EFM MEF* 10 Technical
Specification
Standard
Pre-Standard
Ethernet over Copper
EFM over Copper Active Ethernet Metro Ethernet Category
(inc. T1/E1 or frame
relay replacement)
(inc. T1/E1 or frame
relay replacement)
Residential triple play
Large enterprises Target
Segments
Unlimited for T1/E1;
< 7 km / 4.5 mi. for
SHDSL.bis
Up to 7 km (4.5 mi.) 10–40 km (6–25 mi.)
depending on optics
10–40 km (6–25 mi.)
depending on optics
Reach
1.5–5.7 max Mbps
per pair (to 45 total)
Up to 5.7 Mbps per
pair (max 45 Mbps)
10/100/1000 Mbps 1–10 Gbps Data
Rates
Point to point Point to point Point to point Ring, star Topology
1 to 8 voice-grade
Cat-3 copper pairs
1 to 8 voice-grade
Cat-3 copper pairs
1 single-mode optical
fiber
1 single-mode optical
fiber with WDM
Physical
Medium
A quick reference guide to the four common technology categories
Ethernet
over
Copper
Ethernet
over
Fiber
Ethernet in the First Mile (EFM)
*MEF = Metro Ethernet Forum
SM 0 SMO SMO