encapsulation

Encapsulation

Table of content

• Encapsulation
  • OpenSAND exploitation
  • OpenSAND software design

Inspired from the DVB-S2 and DVB-RCS2 standards, OpenSAND uses different encapsulation mechanism in order to transport network packets (either IP packets or Ethernet frames) on the BBFrame and DVB burst payloads.

OpenSAND uses different protocols depending on the standard. The available protocols are:

• GSE: available for use on the forward link with DVB-S2.
• RLE: available for use on the return link (or uplink and downlink in regenerative mode) with DVB-RCS2.

OpenSAND exploitation

Encapsulation protocols used on both the forward and return links can be configured from the Configuration tab on the OpenSAND manager.

The available protocols for the selected standards are displayed on the boxes under the Encapsulation label. When changing the return link standard (from the Advanced configuration window), the available encapsulations protocols may change on both the forward and return links.

The available encapsulation protocols also vary depending on the type of satellite used (transparent or regenerative).

For more information concerning the specific configuration of each protocol, refer to its page.

OpenSAND software design

Encapsulation in OpenSAND has a dedicated Rt block, called BlockEncapsulation. All terminals and gateways use the BlockEncapsulation. In regenerative mode, satellites use a different BlockEncapsulationSat that implements a reduced set of encapsulation functionalities.

This encapsulation block is in charge of receiving network packets from the upper block (Lan Adaptation), and encapsulating them using the desired protocol. These encapsulated packets will be sent to the lower block (Block DVB) to be transmitted via the satellite link. In the other way, the block is in charge of receiving encapsulated packets, and restoring the network packets to be sent to the upper block.

The encapsulation process is tightly coupled with the scheduling (performed on the DVB blcok): when scheduling packets, the available space on the created BBFrames and DVB bursts may vary. For encapsulation protocols with fixed PDU size, this does not have any impact other than a changing the number of encapsulated PDUs that fit on one BBFrame or DVB burst. For encapsulation protocols with variable PDU size, however, the different size of the BBFrame/DVB burst may condition the size of the encapsulated PDU. This requires interactions between the Block DVB and the Block Encapsulation.

Encapsulation of some protocols (e.g. GSE and RLE) is performed using external libraries. More detailed information available on their respective pages.