User Manual

Chapter 4 - Operation and Administration Using the CLI Managing BSs
4Motion 761 System Manual
In certain cases, such as entity reset, other entities are not aware of service
termination of an MS in that entity, and keep maintaining the MS context. This
may result in service failure, excessive consumption of memory resources and
accounting mistakes.
The keep-alive mechanism should be used to clear MS context from all network
entities when it is de-attached from the BS, and de-register MS from the network
when its context becomes unavailable in one of its serving function locations.
When the keep-alive mechanism is enabled the BS periodically polls other
ASN-GW entities-of-interest and waits for their responses. In case of no keep-alive
response, the BS shall make further actions, such as graceful de-registration of
applicable MS(s) and clearing the applicable MS(s) context.
The BS builds a list of ASN-GW-of-Interest, which it must poll. The list is
dynamically updated; when a new MS is attached to the BS, or MS performs CSN
mobility (data-path relocation) and in its context there is an ASN-GW identifier
unknown to this BS, it shall add it to the ASN-GW-of-interest list. When the last
MS(s) with specific ASN-GW identifier exits the network, the BS shall remove the
ASN-GW from the list. The BS shall include in the ASN-GW-of-interest list also
Relay Data-path ASN-GW(s) (UL next hop IP address). This is applicable when
hierarchical data-path establishment takes place during inter-ASN HO.
The BS periodically polls the ASN-GW(s) for keep-alive. The polling mechanism is
independent and unrelated for every ASN-GW-of-interest the BS polls.
The keep-alive mechanism uses configurable retry timer and retries counter.
Upon expiration of the retry timer, the BS resends the BS Keep-Alive request
message. Upon expiration of the retries counter, the BS assumes failure of the
polled ASN-GW and clears the contexts of all MS(s) served by that ASN-GW.
In addition, the BS verifies that for each polled entity that the "Last-Reset-Time"
UTC value of poll N+1 is equal to the value of poll N. If the "Last-Reset-Time" UTC
value of poll N+1 is higher than the value of poll N, this mean that the ASN-GW
went through reset state during the interval between two consecutive polls. In this
case, the BS shall de-register all MS(s) served by that specific ASN-GW and clear
their contexts.
When keep-alive fails, the BS generates an alarm and log the event.
Regardless of the enable/disable status of the keep-alive mechanism in the BS, it
replies to BS_Keep_Alive_Req received from ASN-GWs with BS_Keep_Alive_Rsp.
that includes also its "Last-Reset-Time". It responds only if all its functions
operate properly. In case one of the functions fails, the BS shall not respond to the
keep-alive poll.