Factors Affecting Advertised Capacity

The following factors affect the IP application’s Advertised Capacity:

• Host card

  Performance Characteristics of the host card can impact the capacity.

• CPU utilization

  Various factors determine the processing resources required by IP applications to manage a given traffic load, and cause the processing of each MSU to be more expensive. For example, the EAGLE provides a feature that enables support of Class-1 Global Title traffic. When the feature is enabled and a triggering message is received by an IP signaling application, the application sends the MSU to an SCCP card for translation, and after translation, the MSU is sent back to the originating IP signaling card for post-translation routing. This extra IMT hop results in significant processing overhead in the receiving IP signaling card.

• Message buffers

  The amount of memory allocated for traffic buffers determines the maximum traffic rate and average message size that can be sustained for a certain network configuration. The buffer size is configurable through associations. For example, within the constraints of memory on the card, each association can have from 8 kb up to 400 kb of send-and-receive buffer space for SCTP.

• Card communication interfaces

  The capacity of the card's external interfaces can become a constraint for certain configurations. For example, the IMT interface capacity is affected by high-utilizing features, or the Ethernet interface configurable capacity is set to half-duplex (not 100Mb/sec full-duplex).

• E5-ENET-B IPSG High Throughput feature

  Turning on the E5-ENET-B IPSG High Throughput feature impacts the baseline configuration for the E5-ENET-B IPSG card as shown in Table 5-5

  Table 5-5 Baseline Configuration Changes for the E5-ENET-B IPSG High Throughput Feature

  E5-ENET-B Card Baseline Configuration	E5-ENET-B when IPSG High Throughput Feature OFF, E5-ENET	E5-ENET-B IPSG High Throughput feature ON
  Maximum TPS for the card	6500	9500
  Average MSU size (bytes)	0-272	0-120
  Max RTT (MS)	120	50
  Max number of links/associations	16	4
  Protocol	M2PA and M3UA	M2PA

• Card de-rating

  If the E5-ENET-B IPSG High Throughput feature is turned on, the traffic rate is greater than 6500 TPS, and the E5-ENET-B IPSG card exceeds the limits shown in Table 5-5, then the card is de-rated according to the following calculations:

  • SLK TU cost factor = 1+ (RoundDown (((Number of links - 1)/4) * 0.025)
  • MSU size TU cost factor for M2PA links = 1+ (RoundUp(((Average MSU size - 120)/10) * 0.012)
  • MSU size TU cost factor for M3UA links = 1+ (RoundUp(((Average MSU size - 120)/10) * 0.02)
  • Association RTT cost factor (if greater than 50) = 1+ (RoundDown((Association RTT/25) * 0.04)
  • Protocol TU cost factor for M3UA links = 1.05

Note:

When calculating the values for the Average MSU SIF size >120, Number of Links >4, and Association RTT > 50, the values from the division in the formula are rounded to the quotient. In addition, the final values for the Transaction Unit Adjustment and Transaction Unit Cost values for Average MSU SIF size are rounded to the nearest 10 value if the delta is not a multiple of 10.

Given the derating factors, a derived SLK IP TPS for an MSU would be calculated as follows:

Derived SLK IP TPS for an MSU = 1 TU (Actual SLK IP TPS) + 
(RoundDown (((Number of links - 1)/4) * 0.025) (for number of links > 4) + 
(RoundUp(((Average MSU size - 120)/10) * 0.012) (for M2PA) OR 
+ (RoundUp(((Average MSU size - 120)/10) * 0.02) (for M3UA) 
+ (RoundDown((Association RTT/25) * 0.04) (for RTT>50 ms) +
0.05 (for M3UA)

For detailed descriptions of factors that affect advertised card capacity, see Engineering Rules for Determining IP7 Application Throughput.