Generic Stream Encapsulation

Generic Stream Encapsulation, or GSE for short, is a Data link layer protocol defined by DVB.

GSE provides means to carry packet oriented protocols such as IP on top of uni-directional physical layers 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: The protocol specification has been published as ETSI TS 102 606.

[1] An accompanying implementation guidelines document has been published as ETSI TS 102 771.

The encapsulation process adds control information such as the network protocol type and address label, and provides an overall integrity check when needed.

GSE Packets have in general variable length, in order to match the input IP traffic with minimum overhead.

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.

GSE relies on the physical layer being able to ensure the required error detection and/or correction probability.

[3] The GSE Packet header is highly dynamic and provides for many options.

On DVB-S2, DVB-T2, and DVB-C2 the ACM/VCM modes may cause the Base Band frames to vary in size depending on the transmission conditions.

Whenever the encapsulator needs to move on to the next payload frame, without having finished transmitting the previous one, it uses the next available Fragment ID.

The "Label Type" (LT) bits determine how the GSE packet address is encoded according to the following table: Each GSE Packet containing the last fragment for a payload frame, carries a CRC-32 checksum over the payload frame.

If the last fragment of a payload frame is lost, the decapsulator can not directly detect that fact.

For this situation, the decapsulator must choose a suitable time-out based on the data-rate and application.

Here is a (very likely incomplete) list of GSE en- and decapsulators: There are many IP-over-satellite service offerings, including for instance ASTRA2Connect from SES or Tooway from Eutelsat.