ND SatCom SKYWAN IDU 7000, Manual

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2010-10-26 Network Design and Engineering Guide 121
Data Networking
SkyWAN
®
Internet Protocol Features
Platinum Dynamic
The Platinum Dynamic forwarding aggregate defines a ’on demand’ real time traffic flow. Ca-
pacity allocation is not done permanently but only if packets matching the aggregate’s definition
are received on the Ethernet port. If the traffic flow stops for more than a configurable timeout
period, the capacity is automatically released by the station. That makes Platinum Dynamic the
optimal forwarding behavior to support real time services like voice and video over IP. The Plat-
inum Dynamic mode has some special configuration options which are discussed in the follow-
ing section.
Flow detection: Platinum Dynamic traffic flows may be detected using 3 different methods
which may be selected by configuration:
-
’flow’ means that a combination of IP source and destination address defines a traffic flow,
- ’microflow’ means that a combination of IP source and destination address together with a
source and destination UDP/TCP port defines a traffic flow.
- ’microflowevenport’ only considers IP packet flows which have even numbered source and
destination UDP/TCP ports as Platinum Dynamic flows. This option takes into account that
many real time applications use the Real Time Transport Protocol (RTP). Media transport
flows are typically using even port numbers, whereas the odd port numbers are used for
signaling messages of the Real Time Control Protocol (RTCP). In this case it makes sense
to treat only the media flows as Platinum Dynamic flows.
The flow detection options are especially important for VoIP applications. If we are using VoIP
gateways in our network multiple calls between these gateways would use IP flows with iden-
tical source and destination addresses. Setting the flow detection parameter to ’flow’ would
consider the streams generated by all the calls as a single IP flow. Choosing ’microflow’ or ’mi-
croflowevenport’ would correctly identify each voice call as an individual Platinum Dynamic
flow. It is sufficient to define a single Platinum Dynamic aggregate for all calls originating from
the VoIP gateway. The maximum number of allowed calls must be defined by the aggregate’s
group multiplier parameter. Each call will trigger a stream slot request according to the aggre-
gate’s configured data rate.
Granularity : Detection of IP flows on the TCP/UDP port level is not always feasible. If for ex-
ample IP in IP tunneling and encryption of user data is used, the Sky WAN
®
IDU cannot evalu-
ate TCP/UDP headers. In this case multiple calls of a VoIP device would be considered as a
single IP flow. The aggregate’s configured data rate must then be set to the requirement of the
maximum possible number of calls. Allocating this rate when only a single call is active would
potentially constitute a waste of bandwidth. In this case the aggregate’s granularity parameter
could be applied. By default it is set to 100% meaning that the detection of the first packet of
the flow would trigger the request for the complete data rate defined in the aggregate. If this
parameter is set to 25%, the requested capacity could be 25%, 50% , 75% or 100% of the con-
figured data rate, depending on the data rate of the incoming flow. For a VoIP device with max.
10 voice calls a granularity of 10% would be chosen and the configured data rate would be set
to the requirement for 10 voice calls.
An additional option for Platinum Dynamic aggregates is header compression which will be
explained in the next chapter.