The DSC - SP2000 Platforms use Stream Control Transmission Protocol (SCTP) for packet-switched SS7 signaling and for Diameter traffic.

For detailed information about configuring SCTP for packet-switched SS7 signaling, refer to Configuring SCTP for M2PA Links and for configuring SCTP Parameter Sets, refer to Configuring SCTP Parameter Sets.

The following sections describe the meaning of the various configurable SCTP parameters supported by the DSC - SP2000 Platforms.

Configuring Heart Beat

The Heart Beat feature sends a test message over the SCTP association to ensure IP connectivity. If enabled, you must also set the delay interval between test messages. This delay interval is set in the Heartbeat Interval attribute and is entered as an integer in milliseconds. For example, enter 1000 for 1 second.

As per section 8.3 of RFC 4960, on an idle destination address that is allowed to heartbeat, it is recommended that a HEARTBEAT chunk is sent once per RTO of that destination address plus the protocol parameter’ HB.interval’, with jittering of +/- 50% of the RTO value, and exponential backoff of the RTO if the previous HEARTBEAT is unanswered.

Configuring Retransmission Time Out

The Retransmission Time Out (RTO) is the amount of time the linkset waits for an acknowledgement before retransmitting messages. The RTO initial is the interval round-trip delay in millisecond (ms). The RTO minimum is the minimum round-trip delay interval in ms. The RTO maximum is the maximum round-trip delay interval in ms.

Setting these RTO attributes can help compensate for IP networks with low reliability levels. Compensation is possible within reasonable limits but for IP networks with unacceptably low levels of reliability, compensation may not be possible.

It is recommended that the setting for RTO Initial is set to less than RTO Maximum and greater than RTO Minimum.

Note

The value of the RTO is recalulated as per RFC 4960 procedures. The recalculated RTO value remains between the SCTP Association RTO Min and RTO Max.

Configuring Retransmission Counters

The Retransmission Counter attributes can be configured to help compensate for network delays. Compensation is possible within reasonable limits, but for unacceptably low levels of reliability, compensation may not be possible.

The Maximum Path Retrans attribute sets the maximum number of times the linkset attempts to retransmit messages over the current transmission path before deeming the path as unavailable and selecting a different IP address. The Maximum Assoc Retrans attribute sets the number of times the linkset attempts to retransmit messages over all possible paths without success before deeming the end device as unavailable and closing the SCTP association.

Configuring Bundling

The Bundling feature enables the bundling of messages into larger packets. Bundling is an effective way to increase efficient usage of network resources on high traffic links.

Note

Bundling Timeout is not available on all DSC Platforms due to differences in the SCTP implementation.

The bundling timer sets the length of time in milliseconds messages are queued before being bundled into a larger packet and sent. This configuration option is not available on all DSC Platforms.


Configuring Delayed Acknowledgment Time Out

The Delayed Acknowledgement Timeout attribute configures the maximum amount of time in milliseconds the linkset waits before sending an acknowledgment after receiving a packet.

Configuring Fast Retransmit

The Fast Retransmit attribute configures the number of times a packet can be reported as missing at the linkset before SCTP retransmits packets on that SCTP association using fast retransmission.

Setting the fast retransmit value too low results in unnecessary retransmissions and inefficient network usage. Setting this value too high results in a loss of performance and increased delay.


  • No labels