This field is used to describe the first least field of total 16 minimum guaranteed rate which is configurable by user for a VCL which is bound to this traffic descriptor for BAN ATM Trunk or MALC uplink Cards. It is applicable only for RTVBR/NRTVBR or CBR service category. For RTVBR/NRTVBR service category, this value can be set in the rfc2515 td_param2 of the traffice descriptor table. For CBR service category, this value can be set in the td_param1 field. The maximum rates capacitiy is 16, any value which is not matched in any one of those 16 rates will be rejected. Unlike switched voice calls in the TDM world we cannot oversubscribe bandwidth because all of our voice calls must be connected at all times so that we can receive signaling to tell us that the phone when off hook. Instead of oversubscribing we suggest that the service provide under provision their voice calls. An example of this would be a normal good quality voice call over ATM requires about 189 CPS. To share the bandwidth resource over several customers the service provider would instead allocate (for example) 38 CPS for a single voice channel, this would allow 5 channels to share the bandwidth required to connect a good quality voice call. Any value less than 189 CPS could be used if the service provider wished to share bandwidth resources over more than one voice call. In order for this method to produce a good quality voice call enough bandwidth must be unallocated and used in a shared pool by all connections. When the buffering is not adequate for a good quality call the connection will not terminate, instead the call quality will suffer. Values greater than 189 CPS would be used by devices like a PBX. This parameter is used independently for transmit and receive traffic based on the traffic descriptor specified for transmit and receive in the VCL.
Sources for this description
Multiple manufacturers; see the original MIB MIB copies (LibreNMS/Observium Community)