Payload Size

For DS3, E3, DS1, and E1 circuit emulation, the payload size can be configurable in number of octets. The default values for this parameter are shown in Table 1. Unstructured payload sizes can be set to a multiple of 32 octets and minimally be 64 octets. TDM satellite supports only unstructured payloads.

For N*64 kb/s circuits, the number of octets or DS1/E1 frames to be included in the TDM payload needs to be configurable in the range 4 to 128 DS1/E1 frames in increments of 1 or the payload size in octets. The default number of frames is shown in Table 2 with associated packet sizes. For the number of 64 kb/s channels included (N), the following number of default frames apply for no CAS: n=1, 64 frames; 2≤N≤ 4, 32 frames; 5≤N≤ 15, 16 frames; N≥16, 8 frames.

For CAS circuits, the number of frames can be 24 for DS1 and 16 for E1, which yields a payload size of N*24 octets for T1 and N*16 octets for E1. For CAS, the signaling portion is an additional ((N+1)/2) bytes, where N is the number of channels. The additional signaling bytes are not included in the TDM payload size, although they are included in the actual packet size shown in Table 2.

The full ABCD signaling value can be derived before the packet is sent. This occurs for every 24 frames for DS1 ESF and every 16 frames for E1. For DS1 SF, ABAB signaling is actually sent because SF framing only supports AB signaling every 12 frames.