Chapter 1: Description and Requirements
Chapter 1: Description and Requirements
The E3Switch TDM-over-PSN pseudowire gateways described herein are used in pairs to extend a full or
fractional E3 or T3/DS3 TDM circuit over an intermediate Ethernet Layer-2 packet switched network
(PSN). The TDM circuit may be channelized or unchannelized and may contain framed or raw/encrypted
data. The gateway will regenerate the outgoing TDM clock and alarm conditions being received at the
remote end.
The LAN interface is RJ45 100/1000BaseTX copper or SFP 1000BaseX fiber optic. The two gateways
must have a LAN between them. Reverse topology, to bridge two LANs over an intermediate E3 or
T3/DS3 circuit, is not possible with this product; for that, please see our LAN Extender product line.
The gateways must be used in pairs. Single-ended operation for connection to a third-party TDMoPSN
gateway is not supported.
For ease of installation, the gateway requires minimal configuration, and, for full-rate E3/T3, will typically
work immediately upon connection of LAN and TDM cables.
The hot-swappable gateway card may be purchased in standalone or multi-card chassis and draws a minimal
6 watts of power. Standalone, single units ship in high-reliability, fan-free 1U chassis with rackmount
brackets and are available in a 100-240VAC or a
±35-
75 volt DC models. NEBS-III, redundant-power
multicard chassis are available in 6-slot/1U and 20-slot/3U versions.
Both HTTP and SNMP management of the gateways is possible either in or out-of-band through either the
copper or SFP LAN port. An SFP transceiver is required to use the SFP LAN port.
Remote firmware upgrade to a gateway is possible through the LAN port, but may require a 15-second
outage during gateway reboot.
While the hardware for two TDM circuit connections is present on the unit, only one, bidirectional circuit is
currently supported.
The gateway will buffer data from the LAN to remove jitter, and implements quality-of-service mechanisms
to eliminate data loss. Packets received out-of-sequence will be properly reordered when possible. The
depth of the jitter buffer may be configured to achieve minimum latency. The number of bytes per packet is
configurable to allow balancing of bandwidth vs latency according to user's desire.
The gateway supports VLAN tagging, Type of Service (ToS) and DiffServ configuration.
A gateway's configuration must be manually set via the LAN port. The gateways do not currently auto-
negotiate parameters of the pseudowire connection.
The gateway has been designed with attention paid to minimum latency and minimal packet loss –
containing resequencing functionality that may not be present in other products. The gateway is often a
cost-effective and simpler alternative to a router. Even when connected to a LAN port on a router,
eliminating a router TDM card can free up expensive, limited, router backplane bandwidth .
The gateway is plug-and-play and can often be installed in several minutes. Network topologies and
configuration settings of equipment connected to the gateway can be complex, however, so additional time
should be allocated to achieve a properly functioning system.
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