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What does drop type 'SIP Bye Request' in tems mean?


Hi expert,

I came across one type of drop call in tems.

Drop Type: ‘SIP Bye Request’ failure

Can anyone help me to the the reason for this


What is the reason code for this

Multiple reason behind this


Wait I’ll share code

But what are the generic reason for this drop


The code is 503


Please explain…

What will be the action plan


This all are 18 xxx cause code

All related to registration fail

Most of the network facing this for this you guys have to tune S1 link and Nas optimisation


S1 -U or S1-C …


U will come after c


90,91,93 cause code :no_mouth:



In volte there are two types of cause code

When cause code come that means call drop or call block not in picture cause code means service affected which is indirect to call block muting and etc

When reason code comes that is the main thing

Where a particular shit happens because of that reason


But here are discussion On RLF means drop it is mostly in u plane


Yes you right


C- plane cause code please explane


If you want to save drop because of rlf you can extend timer in sync and out sync

And extended RLF FEATURE this can also help to reduce drop


Its all know


do you guys have partial drops???


How we can identify the RLF failure at MME end any specific cause code


In mean drop due to partial handover

No specific cause code drop happens on cell edge where coverage week in 4g because of restblishment drops are less


No its paging in Total drop but not in Active E-Rab


Which BTS??? Ericsson or Nokia