I have a customer who has the following setup:
SIP Provider => MPLS => CUBE (SIP) => CCM (SIP) - cube set for passthu using NSE
CCM (MGCP) => VG224 - set for passthu using NSE
CCM (SIP) => Cisco RightFax - set for T38 with passthru failover (realize it is protocol xfer)
CCM (MGCP) => Router with tieline to PBX - set for passthu using NSE
- all g711ulay with no vad (and default 20ms samples for lack of a better term)
Testing, minimal, currently works from:
- PSTN to VG224 (both ways)
- Rightfax to VG224 (both ways)
Questions
1. PSTN=> VG224
- capture shows initial g711u negotiated (see attached flow graphic form wireshark)
- as expected, vg224 sending NSE to switch and provider ignore (no RTP 192 ack ever)
- fax still goes through, only doing 1-2 pages
- working in both directions even though see Cisco side always trying NSE switch unsuccessfully
Q1: why does this work?
Q2: Will it work consistently for large faxes or faxes that have images?
Q3: since NSE does not work, can I assume no switch to 10ms sample: what impact to quality?
2. Rightfax to VG224
- same thing here, NSE is ignored as expected
- but fax still worked in both directions
I am asking becuase this is not yet in production and our sample faxes have been 1 to 2 pages and also we are not yet doing any volume.
Design :
- T38 from Rightfax <=> ITSP (works fine)
- would love to do T38 across board but ITP does not support T38 re-invite for PSTN bound faxes
o and I am told Cisco will not re-invite of not on terminating side (Rightfax does)
- just provided this for big picture (anticipating recommendations)
Summary
- just why are the passthroughs working for flows that are terminating on non-Cisco gear
- associated concern about reliability
- associated concern about fax quality
Thank you!
Andy
