Comtech EF Data CDM-750 - Manual (Page 86)

CDM-750 Advanced High-Speed Trunking Modem Revision 2
Front Panel Operation MN-CDM750
5–8
5.2.2.1.1 Single Stream Mode vs. MultiStream Mode Operation
Single Stream Mode is the conventional way to transport a single type of traffic data over
satellite, whereas MultiStream Mode allows more than one type of traffic data to be active at
the same time. Note the following:
• For Single Stream Mode:
1. A single PIIC module is installed and active and all other interfaces are either not
installed (i.e., NONE) or are installed but not active (i.e., Off), or
2. Any combination of Gigabit Ethernet (GBE1 / J5 | DATA port, GBE2 / J6 |DATA port,
or Optical / J7 | OPTICAL port) is enabled, but neither PIIC slot is active (i.e., NONE
or Off).
The three Gigabit Ethernet data interfaces are considered a single data
interface type, regardless if one or more of these interfaces are active.
• For MultiStream Mode:
1. MultiStream Mode is an internal multiplexing (MUX) and de‐multiplexing (De‐MUX)
of data interface types, which allows two or more data traffic types to co‐exist
simultaneously in a single carrier.
2. One or more of the GbE interfaces MUST be active in order to enter or exit from
MultiStream Mode. Therefore, at least one of the GbE interfaces must be active at
the same time that at least one of the PIIC slots is active (e.g., PIIC1=G703‐E3). The
CONFIG: Intf screen display example shows the modem in MultiStream Mode.
3. Adaptive Coding and Modulation (ACM) is non‐functional while in MultiStream
Mode. All other WAN optimization features (Carrier‐in‐Carrier, GZip compression,
etc.) are functional in MultiStream Mode.
4. Because MultiStream Mode is a MUX of different data types, there is overhead
associated with the total MUX structure. This associated overhead is 1.5% of the
aggregate non‐Ethernet data in Normal Block Mode, and 5% in Short Block Mode.
For example: You are running a link, using Normal Block Mode, that is using
MultiStream to aggregate Ethernet traffic and two G.703 E3 (34.368 Mbps)
connections. The computation of the modem Tx link’s configuration for minimal
support is therefore
(34.368+34.368)*1.015=69.768 Mpbs. Any data rate
that is ABOVE this minimum data rate is given to the GbE interfaces – meaning, per
the preceding computation, if the modem Tx was set to 100 Mbps, then the
remaining 30.232 Mbps
(100Mbps–69.767Mpbs=30.232Mbps)would be
allocated to the Ethernet traffic type.