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Vinay Sharma
Rising star
Rising star

 

Introduction

Q&A Session for  Technical Service Virtual Boot camp - Session 6

Q: ­Could you please explain a bit about Expires & Session-Expires Header and Min-SE?

­A: ­Session-Expires header talks about the maximum time an INVITE would stay valid, before it has been addressed, where as the Min-SE value is session dependent­.

Q: ­What about the field Expires:180?­

A: ­I believe you want to mention 1800 rather­. The invite message has a expires header field­.

Q: ­The logs we are discussing this time are all we can see through Wireshark?­

A: ­Both a Wireshark or a translator x or a regular notepad ++ for a call manager trace file can be used to review­.

Q: ­We see c=0.0.0.0 going to ITSP­, why?

A: ­So does that c=0.0.0.0 and a=inactive at the same time­.

Q: Can it be modified as m=sendonly?­

A: ­a=sendonly indicates that the call is on hold­.

Q: ­How many such keep alive will be sent­?

A: ­6­ keep alives will be send.

Q: ­How the connectivity is there between SIP server and CUBE? Is it through sip trunk connection through e1/t1?­

A: ­CUBE is always an IP to IP arrangement, so has to be an ITSP­.

Q: ­We would like to use a=sendonly, not c=0.0.0.0, is that possible?­

A: ­I doubt it is configurable and made to be triggered.  c=0.0.0.0 is no longer recommended per RFC2543, you would see a confirmed reply on the CSC page, would update.­

Q: ­What is the meaning of C=IN 0.0.0.0­?

A: ­c line is the ip address or the hostname that the originator expects the media to arrive at­‑ ­the IP= 0.0.0.0 indicates.­

Q: How do destination know the c ip­ ack of the 200OK ­‑with SDP­? Is there any difference in call flow if we use SIP with UDP or TCP?­

A: I don't think there is any fundamental difference apart from the fact the transport type changes, so reliability of message delivery is different.­

Q: ­Will the PRACK have an incremental CSEQ?­

A: ­Yes it would have­.

Q: ­Can you brief PRACK?­

A: ­This would be revisited in detail on the CUCM.

Q: ­In C=IN 0.0.0.0 , which IP is 0.0.0.0?­

A: ­This is a method per rfc to share that the call is on hold­.

Q: ­Media negotiation done by RTP, then what SDP does actually? ­What is P-time in SDP parameter?­

A: ­Email address and phone numbers can be shared in e and p lines, we don’t necessary see these in cisco devices to have this in their sdp.­

Q: ­Will SIP over TCP have to open the TCP socket first before send the INVITE?­

A: ­SIP stack contains a transport layer and needs to have a valid TCP session for addressing incoming INVITES­.

Q: ­In Order to convert the inband-dtmf to RFC2833, does the CUBE need local Transcoders (transcoder should be registered in CUBE itself)?­

A: ­A xcoder necessarily is not needed to mitigate a DTMF mismatch a xcoder when taking a role of an MTP can mitigate DTMF mismatch.  CUBE local resources can be used for the mismatch, there are lot more specific scenarios based on which we would have. If you can specify exactly what dtmf relay mechanisms exist on the cube inbound and outbound dial-p then would be able to be better comment.­

Q: ­Are the DTMF digit sent during SDP offer?­

A: ­NO , what depends is what kind of a DTMF mechanism are we doing.­‑ A SIP KPML is a subscribe while a SIP notify is a NOTIFY method­.

Q: Can we have a complete session on monitoring again in a more elaborated way?

A: ­sure we can .. would raise that as a request and let you know.­

Q: ­When the far end device doesn't respond to OPTIONS Ping Message, will the RTMT send alert for the failure? if not, how will we come to know whether the destination is out of service?­

A: ­This needs a recreate.. good find.  I don’t think that has been integrated yet, would update.­

Q: ­What is the use of collect the files in last 5 minutes there­?

A: ­That is used for a relative range. For servers in different timezone, whichever has been the last 5 minutes from each server logs would be pulled for those.­

Q: ­From where TranslatorX tool can be downloaded?­

A: ­http://translatorx.cisco.com/­

Q: ­Do u always use TranslatorX tool to analyse rtmt logs? ­

A: ­Not quite, for issues which don't have to deal with call flows, and need device layer review or other components notepad ++ can be preferred­.

Q: ­Can we avail translator X tool from cucm server?­

A: It is not part of the package but is a freeware.­

Q: ­Wireshark plays only 711 codec? how can we play g729 codec from Wireshark?­

A: ­There is a decoder which is codec in c language which can be used. Native support of g729 codec does not exist yet.­

Q: ­What about video play?­

A: Video sampling is a still a enhancement for the tool­.

Q: ­Can we analyse video traffic as well?­

A: ­Video packets cannot be sampled­.

Q: ­What is the link for registering " month of voice technology" session?­

A: ­https://supportforums.cisco.com/docs/DOC-38598­.

Q: Where can i find all previous session information?

A: https://supportforums.cisco.com/document/12018656/technical-services-virtual-boot-camp-series

Reference

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