Cisco Unified CME VoIP Call Transfer Options

Your Cisco Unified CME system by default is set up to allow local transfers between IP phones only. It
uses the Cisco H.323 call transfer extensions to transfer calls that include an H.323 VoIP participant.
To configure your Cisco Unified CME system to use H.450.2 transfers (this is recommended), set
transfer-system full-consult under the telephony-service command mode. You also have to use this
configuration for SIP VoIP transfers.
To configure your Cisco Unified CME system to permit transfers to nonlocal destinations (VoIP or
PSTN), set the transfer-pattern command under telephony-service. The transfer-pattern command
also allows you to specify that specific transfer-to destinations should receive only blind transfers. You
also have to use this configuration for SIP VoIP transfers. The transfer-pattern command allows you to
restrict trunk-to-trunk transfers to prevent incoming PSTN calls from being transferred back out to the
PSTN (employee toll fraud). Trunk-to-trunk transfers are disabled by default, because the default is to
allow only local extension-to-extension transfers.
To allow the H.450.12 service to automatically detect the H.450.2 capabilities of endpoints in your
H.323 VoIP network, use the supplementary-services command in voice service voip command mode.
To enable hairpin routing of VoIP calls that cannot be transferred (or forwarded) using H.450, use the
allow-connections command. The following example shows a call transfer configuration using this
command.
voice service voip
   supplementary-service h450.12
   allow-connections h323 to h323
telephony-service
   transfer-system full-consult
   transfer-pattern .T
The configuration shown in the preceding example turns on the H.450.2 (transfer-system full-consult)
and H.450.12 services, allows VoIP-to-VoIP hairpin call routing (allow-connections) for calls that don’t
support H.450, and permits transfers to all possible destinations (transfer-pattern). The transfer
permission is set to .T to provide full wildcard matching for any number of digits. (The T stands for
terminating the transfer destination digit entry with a timeout.)


The following example shows a configuration for more restrictive transfer permissions.
telephony-service
   transfer-system full-consult
   transfer-pattern 1...
   transfer-pattern 2... blind
This example permits transfers using full consultation to nonlocal extensions in the range 1000 to 1999.
It also permits blind transfers to nonlocal extensions in the range 2000 to 2999.


Notes Regarding H.450.12 and ECS


H.450.12
You can compromise between the H.450.2 and hairpin routing call methods by turning on the H.450.12
protocol on your Cisco Unified CME system (this is recommended). You must be using at least
Cisco Unified CME 3.1 to use H.450.12. With H.450.12 enabled, your Cisco Unified CME system can
use the H.450.12 protocol to automatically discover the H.450.x capabilities of VoIP endpoints within
your VoIP network. When H.450.12 is enabled, the Cisco Unified CME system can automatically detect
when an H.450.2 transfer is possible. When it isn’t possible, the Cisco Unified CME system can fall back
to using VoIP hairpin routing. Cisco Unified CME also can automatically detect a call from a
(non-H.450-capable) Cisco Unified CallManager.


Empty Capabilities Set
For the sake of completeness, it is worth mentioning a fourth alternative for call transfers: Empty
Capabilities Set (ECS). Cisco Unified CME does not support the instigation of transfer using ECS. But
because a Cisco Unified CME router also has the full capabilities of the Cisco IOS Release H.323 voice
infrastructure software, it can process receipt of an ECS request coming from a far-end VoIP device. In
other words, a Cisco Unified CME system can be a transferee or transfer-to party in an ECS-based
transfer. A Cisco Unified CME system does not originate a transfer request using ECS. The problem with
ECS-based transfers is that in many ways they represent a combination of the worst aspects of the
end-to-end dependencies of H.450.2 together with the cumulative problems of hairpin for multiple
transfers. Many ECS-based transfer implementations do not allow you to transfer a call that has already
been transferred in the general case of VoIP intersystem transfers.

Disclaimer : The Extract is from Cisco Systems Documentation

Demystifying Mpps

Throughput Parameter regarding switches has always been an ambiguity, finally i manage to crack it, with some help from guislar and ganesh @ Cisco Netpro.

2960-48PST-S -- 13.3 Mpps

The figure Mpps expresses the maximum number of frames per second that can be processed by the device.
It is not dependent on frame size but clearly small frames require higher packet rates.

To give you an idea of what this number says:
smallest frames in ethernet are 64 bytes in size, taking in account the preamble (8 bytes) and the minimum interframe gap (the last two counts roughly for 20.2 bytes) to fill a GE port in one direction you need
1484560 frame per second.

10^9 / [(64+20,2)*8]

where 8 is bits/byte

so a number of 13.3  Mpps is equivalent to ((13.3 M * (64+20.2) * 8 )) / 10^9 = 8.95 / 2 = 4.47 GE ports filled with smallest frames bidirectional.

on the other hand frames of max size 1518 bytes require 81264 fps to fill a GE port in one direction.

So this number expresses the forwarding capability of the device.
A non blocking device with 48 GE ports would require 2 * 1484560 * 48 as Mpps or higher.

A device like C2960 can be classified as centralized CEF forwarding.


Mpps regarding routers,

MPPS stands for million packets per second and Cisco prefers to refer throughput in MPPS.For a layer-3 switch an Mpps value is shared one. For some of the higher-end cisco routers the routing is "distributed" between multipe line-cards, in which case the PPS numbers are based on the number of line cards, bit for non-distributed architectures (Catalyst switches) the numbers are based on the routing engine, so it is the maximum number of Packets Per Second that the box can route.

and as giuslar said 2960 switches are centralized cef based forwarding.

Switching capacity vs Throuhput

Cisco Catalyst 4900 Series Switch Model Comparison for Fiber Aggregation

Feature and Description	Cisco Catalyst 4928 10 Gigabit Ethernet Switch
Switch Capacity	96 Gbps
Throughput	71 mpps

Switching capacity is some times given as  the amount of frames a switch can deal with over a given time frame and throughput on the other hand means  how much actually data can cross the switch in a given time frame.