Interface Subsystem; Ip Gateways - Hughes HX System System Overview

Interface subsystem

The interface subsystem includes the IP gateway (core
component) and special services gateway (optional component;
described in Special Services Gateway (SSGW) Installation,
Operation, and Maintenance Manual (1032030-0001).

IP gateways

The IP gateways provides the interface between the HX gateway
and the enterprise intranet terrestrial data connections. The IP
gateway performs the IP address mapping, packet transmission,
compression, and other functions needed to support the HX
satellite routers. Traffic between the IP gateway and the intranet
host uses a standard IP packet format. However, the IP gateway
implements an Hughes-proprietary protocol between itself and
the satellite routers that is optimized for efficient, yet reliable
communication over the satellite link.
To facilitate data transfer from the IP gateway to the satellite
gateway, the IP gateway encapsulates unicast and multicast
frames containing traffic destined for satellite routers within User
Datagram Protocol (UDP) packets. The IP gateway obtains the
encryption information from the CAC, then encapsulates and
sends the appropriate unicast data and keys information to the
satellite gateway where the traffic stream is encrypted.
IP gateways forward the encapsulated unicast and multicast IP
traffic from the customer network to the satellite gateway over the
satellite LAN for further outroute processing. Unicast traffic is
addressed to a specific satellite router; multicast traffic is sent to
satellite routers in a pre-defined group and can include
management traffic or user traffic.
The IP gateways record statistics files that contain the amount of
traffic that has been processed for each IP subnet. IP gateways are
designed as a warm redundant pair with online and standby
modes of operation. IP gateways are SNMP-enabled and are
configured, controlled, and monitored by Vision UEM running on
the NMSS.
For TCP traffic, the IP gateway implements
performance-enhancing proxy (PEP) features. See Performance
Enhancing Proxy (PEP V3) on page 52 for a description of the
PEP feature.
The IP gateway functionality also includes support for
multicasting services. In this mode of operation, the IP gateway
forwards multicast data (such as multimedia and advertising
content) through the satellite gateway to the remote sites that are
enabled (using the conditional access system) to receive the
multicast stream. Additionally, each IP gateway can also be
Chapter 2 • Subsystems
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1037852-0001 Revision A