Generic Stream Encapsulation: Difference between revisions

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{{External links|date=September 2022}}

{{IPstack}} '''Generic Stream Encapsulation''', or GSE for short, is a [[Data link layer]] protocol defined by [[Digital Video Broadcasting|DVB]]. GSE provides means to carry packet oriented protocols such as [[Internet Protocol|IP]] on top of uni-directional [[physical layer]]s such as [[DVB-S2]], [[DVB-T2]] and [[DVB-C2]].

GSE provides additional features beyond the pure carriage of IP datagrams that increase the protocol flexibility and applicability. Some key GSE functions/characteristics are:

* Support for multi-protocol encapsulation ([[IPv4]], [[IPv6]], [[MPEG]], [[Asynchronous Transfer Mode|ATM]], [[Ethernet]], [[IEEE 802.1Q|802.1pQ]] [[VLAN]]s, etc.)

* Transparency to network layer functions, including [[Internet Protocol|IP]] [[encryption]] and IP [[Van Jacobson TCP/IP Header Compression|header compression]].

* Support of several addressing modes. In addition to the 6-byte [[MAC address]] (including [[multicast]] and [[unicast]]), it supports a MAC address-less mode, and an optional 3-byte address mode.

* A mechanism for fragmenting [[Internet Protocol|IP]] [[datagrams]] or other [[network layer]] [[Packet (information technology)|packets]] over [[baseband|Base Band]] frames to support [[Link adaptation|ACM]]/[[Variable Coding and Modulation|VCM]].

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GSE Packets may be sent in different Base Band frames, not necessarily consecutive or with the same transmission parameters (modulation format, coding rate). No constraint on the GSE Packet position within the Base Band frame is assumed. However, GSE Packets may not be reordered between the encapsulator and the de-encapsulator. In general, a Base Band frame can contain more than a single GSE Packet. Base Band frames may have fixed, or variable length.

GSE does not provide a mechanism for integrity check of single GSE Packet. A [[CRC-32]] is only appended to the last fragment of a fragmented payload to verify the correctness of the reassembly operation. GSE relies on the physical layer being able to ensure the required error detection and/or correction probability.<ref>IETF RFC{{IETF RFC|3819}}: "Advice for Internet Subnetwork Designers"</ref>

=== GSE Header ===

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| colspan="8" bgcolor="#CCFFCC"| Total Length

| colspan="16" bgcolor="#CCFFCC"| Protocol Type

| colspan="8" bgcolor="#CCFFCC"| Label (3 Bytebytes)

|-

! 64

| colspan="16" bgcolor="#CCFFCC"| Label (continuation, length 3 Bytebytes)

| colspan="16" bgcolor="#AADDBB"| Label (continuation, length 6 Bytebytes)

|-

! 96

| colspan="8" bgcolor="#AADDBB"| Label (continuation, length 6 Bytebytes)

| colspan="24" bgcolor="#FFBBBB"| [[Unidirectional Lightweight Encapsulation|ULE]] Extension Headers (Optional)

|-

! ...

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|-

| 11

| style="text-align:left" | Label re-use: no label is present; the label is the same as the previous GSE packet in the same base band frame. LT=11 is also used for intermediate and end packets (''i.e.'' Start bit 0). LT=11 shall not be used for the first GSE packet in a base band frame with Start bit 1.

|-

|}

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Here is a (very likely incomplete) list of GSE en- and decapsulators:

* [https://web.archive.org/web/20120517023254/http://www.newtec.eu/ Newtec]

** [http://www.newtec.eu/products/professional-equipment/elevation/modems/ip-satellite-modem-el470/ EL470 IP Satellite Modem]

** [http://www.newtec.eu/products/professional-equipment/elevation/demodulators/ip-satellite-demodulator-el970/ EL970 IP Satellite Demodulator]

* [http://www.work-microwave.de/ WORK Microwave GmbH]

** [http://www.work-microwave.de/dvb-s_s2.html#modems Challenge Series Satellite High Speed DVB-S2 IP Modem SK-IP] {{Webarchive|url=https://web.archive.org/web/20110410220742/http://www.work-microwave.de/dvb-s_s2.html#modems |date=2011-04-10 }}

* [http://www.tebkom.at/ Tebkom GmbH]

** [https://web.archive.org/web/20150707163826/http://www.tebkom.at/product_odg.html ODG200 IP/DVB-S2 Encapsulator/Modulator with ACM support]

* [http://www.advantechwireless.com/ Advantech Wireless Inc.]

** [https://web.archive.org/web/20110903085805/http://www.advantechwireless.com/catalogue/products/amt75e-dvb-ss2-high-speed-broadcast-modem-2/ AMT 75e DVB-S/S2 High Speed Broadcast Modem]

* [http://www.comtechefdata.com/ Comtech EF Data Corporation]

** [http://www.comtechefdata.com/products/Advanced-VSAT-Series/pcdm-840.asp CDM-840 Remote Router]

* [http://www.transplaneta.com/ K.S.Transplaneta Ltd.]

** [https://web.archive.org/web/20120322130601/http://www.transplaneta.com/products/ip-encapsulator dpi4502 DVB2 (S2/T2/C2) compliant IPv4 / IPv6 Encapsulator]

* [http://dveo.com/ Computer Modules, Inc.]

** [http://dveo.com/broadcast-systems/ip-over-dvb-encapsulator.shtml DVB Rocket™/S2]

* [http://www.ayecka.com/ Ayecka Communication systems LTD]

** [http://www.ayecka.com/products-SR1.html/php#SR1 SR1 - Advance DVB-S2 demodulator with hardware based , wire speed, GSE Decapsulator]

** [http://www.ayecka.com/products-ST1.html/php#ST1 ST1 - Advance DVB-S2 modulator with hardware based, wire speed, GSE encapsulator]

** [http://www.ayecka.com/products-SM1.html/php SM1 - Advance DVB-S2 Modem with hardware baedbased, wire speed, GSE EnCapsulator / DeCapsulator]

=== GSE-based IP Service Offerings ===

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* [http://www.dvb.org/technology/standards/index.xml#multiplexing Obtain GSE Standard and Guidelines from DVB free of charge]

* [http://www.dvb.org/technology/fact_sheets/DVB-GSE-Fact-Sheet.0709.pdf DVB Fact Sheet on GSE]

* [https://web.archive.org/web/20110722013509/http://telecom.esa.int/telecom/www/object/index.cfm?fobjectid=30265 GSE project home page] at [[ESA]]]

* [httphttps://launchpadgithub.netcom/libgseCNES/libgse Opensource implementation of GSE]

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[[Category:Television technology]]

[[Category:Link protocols]]