Tail-End Hop–Off (TEHO)
TEHO extends the abstraction of toll-bypass. Instead of alone acquisition intersite calls over an
IP WAN link, TEHO additionally uses the IP WAN articulation for PSTN calls. The ambition is to avenue a call
using the IP WAN as abutting to the final PSTN destination as possible. As with toll-bypass,
PSTN fallback should consistently be accessible in case the IP WAN articulation fails.
Chapter 7: Configuring Advanced Dial Plans 409
IP WAN
PSTN
R1
10.10.0.2 10.10.0.1
Phone1-1
2001
Phone1-2
2002
Phone2-1
2001
Phone2-2
2002
Austin
Site Code: 802
San Jose
Site Code: 801
R3
1
User dials 801-2001.
2
Phone1-1 rings.
Calling number:
802-2002
Note Some countries do not acquiesce TEHO. When implementing TEHO, ensure that the
deployment complies with civic acknowledged requirements.
TEHO Example
Figure 7-25 shows the TEHO book for this example.
410 Authorized Self-Study Guide Cisco Articulation over IP (CVOICE)
IP WAN
PSTN
408...
R1
DID: 408555XXXX
Phone1-1
2001
Phone1-2
2002
Phone2-1
2001
Phone2-2
2002
Austin
San Jose
R3
DID: 512555XXXX
1
User dials
9 1 408 555-6666.
4
San Jose PSTN
phone rings.
2
Call is baffled to San Jose
via the WAN.
V
Local San Jose gateway
is acclimated as the PSTN breakout.
3
Figure 7-25 Tail-End Hop-Off Scenario
Here is the action the alarm goes through:
1. Phone2-1 dials 9 1 408 555-6666 (that is, it places a alarm to a PSTN buzz amid in
San Jose).
2. The alarm is baffled to San Jose application the IP WAN link.
3. The bounded San Jose articulation aperture is acclimated to avenue the alarm as a bounded alarm to the San
Jose PSTN.
4. The San Jose PSTN buzz rings.