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Community Member

TFTP server on IP Phone (branch office)

Can we can use a IP Phone to act as the TFTP server for the other IP phones in the local office ? (save us bandwidth across the WAN)

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: TFTP server on IP Phone (branch office)

Nicholas,

Yes we can. The feature is known as Peer Firmware Sharing.

The Peer Firmware Sharing feature provides these advantages in high speed campus LAN settings:

•Limits congestion on TFTP transfers to centralized TFTP servers

•Eliminates the need to manually control firmware upgrades

•Reduces phone downtime during upgrades when large numbers of devices are reset simultaneously

In most conditions, Peer Firmware Sharing optimizes firmware upgrades in branch deployment scenarios over bandwidth-limited WAN links.

When enabled, it allows the phone to discover like phones on the subnet that are requesting the files that make up the firmware image, and to automatically assemble transfer hierarchies on a per-file basis. The individual files making up the firmware image are retrieved from the TFTP server by only the root phone in the hierarchy, and are then rapidly transferred down the transfer hierarchy to the other phones on the subnet using TCP connections.

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7970g_7971g-ge/english/6_0/administration/guide/7970set.html#wp1179668

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7970g_7971g-ge/firmware/8_3_1/english/release/notes/70831.html#wp118163

Hope this helps.

Regards,

Michael.

12 REPLIES
Cisco Employee

Re: TFTP server on IP Phone (branch office)

Nicholas,

Yes we can. The feature is known as Peer Firmware Sharing.

The Peer Firmware Sharing feature provides these advantages in high speed campus LAN settings:

•Limits congestion on TFTP transfers to centralized TFTP servers

•Eliminates the need to manually control firmware upgrades

•Reduces phone downtime during upgrades when large numbers of devices are reset simultaneously

In most conditions, Peer Firmware Sharing optimizes firmware upgrades in branch deployment scenarios over bandwidth-limited WAN links.

When enabled, it allows the phone to discover like phones on the subnet that are requesting the files that make up the firmware image, and to automatically assemble transfer hierarchies on a per-file basis. The individual files making up the firmware image are retrieved from the TFTP server by only the root phone in the hierarchy, and are then rapidly transferred down the transfer hierarchy to the other phones on the subnet using TCP connections.

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7970g_7971g-ge/english/6_0/administration/guide/7970set.html#wp1179668

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7970g_7971g-ge/firmware/8_3_1/english/release/notes/70831.html#wp118163

Hope this helps.

Regards,

Michael.

Community Member

Re: TFTP server on IP Phone (branch office)

Michael,

One question here - is peer firmware sharing limited only to certain models of phones ( like 7970 etc)?

Regards,

Abhijit.

Cisco Employee

Re: TFTP server on IP Phone (branch office)

Hi Abhijit,

Peer File Sharing is applicable to 3rd generation Cisco IP Phones which include:

• 7906

• 7911

• 7931

• 7941 7961 (Gig and non gig)

• 7970 7971

PFS is not applicable to 2nd generation phones like the 7960/40 phones.

Hope this helps.

Regards,

Michael.

Community Member

Re: TFTP server on IP Phone (branch office)

Thanks Michael, what is the differnce between a 2nd-generation & 3rd generation phone?

Regards,

Abhijit.

Cisco Employee

Re: TFTP server on IP Phone (branch office)

Hello again Abhijit,

The differences between the 3rd generation (TNP-based) and the legacy phones just boils down to features and capabilities. As new requirements are being added of the phones, the TNP-based phones have proved to be best able to support these new features. Some of the features available in TNP-based phones that are not available in the legacy phones include:

- support for 802.3af vs Cisco PoE

- support for 10/100/1000BaseT vs 10/100BaseT

- Support for advanced XML applications

- Higher resolution display

- support for advanced security features

Here's a link that compares models:

http://www.cisco.com/en/US/partner/products/sw/voicesw/products_category_buyers_guide.html#number_1

And here's one that links to details of each model:

http://www.cisco.com/en/US/partner/products/hw/phones/ps379/prod_models_home.html

I hope this helps.

Regards,

Michael.

Community Member

Re: TFTP server on IP Phone (branch office)

Thanks for all the mind-blowing stuff Michael! I have one query here though - what does " Support for IEEE standard 802.3af inline power and Cisco inline power" mean? It seems a 7941G has it while 7940 doesn't. Normally people connect a 7940 to a POE switch. Can a 7941G be connected to a non-POE switch?

Hall of Fame Super Red

Re: TFTP server on IP Phone (branch office)

Hi Abhijit,

Hope today finds you well buddy! I hope Michael doesn't mind me weighing in on this. I'm sure he will add some excellent info as well!

Here is some related info (note that all competitors now use 802.3af);

This describes the differences between the older Cisco Inline Power (proprietary) also known as Cisco Pre-Standard PoE and the Standards based 802.3af. All Cisco IP Phone require power either via a PoE switch or local/desktop power (even the 7941G :);

Cisco Inline Power and IEEE 802.3af

Cisco launched Cisco Inline Power in March 2000 and has shipped more than 16 million inline power capable ports on the Catalyst switches. This innovation was quickly recognized within the industry and the IEEE started work to standardize Power over Ethernet implementations such that multi-vendor interoperability was enabled. With the ratification of IEEE802.3af, as with other Cisco innovations, Cisco will support both IEEE 802.3af and prestandard Power over Ethernet concurrently. Cisco has also extended prestandard power management extensions using Cisco Discovery Protocol negotiation to Cisco IEEE 802.3af compliant devices to further optimize PSE power management.

Applying Power over Ethernet requires that the device type be resolved to ensure that power is not applied to nonpower capable devices. To prevent unfortunate mishaps and to reduce the burden of network administration, Cisco and the IEEE devised mechanisms whereby the switch is able to determine whether a powered device or a nonpowered device is attached to a port. However, the phone detection mechanisms used by the Cisco prestandard Power over Ethernet implementation and IEEE802.3af are different in that the Cisco prestandard Power over Ethernet implementation uses AC powered device detection and IEEE 802.3af uses DC powered device detection. DC detection differs from AC detection in that AC detection transmits a low frequency AC signal and expects the same signal to be received back on the receive pair. DC detect applies a DC Current and detects the presence of a powered device by measuring the load applied by the powered device. It should be noted that Cisco IEEE 802.3af compliant devices support prestandard and IEE 802.3af detection mechanisms.

Using a Cisco inline power capable switch or Power Sourcing Equipment (PSE), the switch port will send discovery signals on active and inactive Ethernet ports to detect whether a powered device is present or not. It should be remembered that the powered device will not be powered at this time and therefore cannot bring the link up. It is therefore necessary to transmit the discovery signal on a continuous basis as a powered device may be plugged into the port at anytime.

Within a Cisco prestandard powered device, a low pass filter that is connected between the powered devices receive and transmit pairs allows the low frequency discovery signal to loop back to the PSE. A low pass filter is used as it allows the phone discovery signal to loop back to the PSE, but prevents 10/100 or 1000Mbps frames from passing between the receive and transmit pairs. Once the PSE detects that a powered device is attached to the port, the Cisco PSE will apply power to the port.

By contrast, the IEEE 802.3af-2003 standard uses a different powered device detection technique that uses DC detection to determine whether a powered device is attached and to which power classification the device belongs. An IEEE 802.3af-2003 PSE achieves this by applying a DC voltage between the transmit and receive pairs and measuring either the received current (Amps) or voltage (V) received.

continued on next post......

Hall of Fame Super Red

Re: TFTP server on IP Phone (branch office)

from previous

Once a powered device has been discovered, an IEEE 802.3af PSE may optionally perform powered device classification by applying a DC voltage and current to the port. If the powered device supports optional power classification it will apply a load to the line to indicate to the PSE the classification the device requires by attenuating the DC voltage. The PSE then determines the powered device's classification using the Volt-Amp (VA) slope returned by the powered device's signature. If the powered device does not support classification, the powered device is assigned to Class 0, the default class.

Once the PSE has detected the powered devices IEEE 802.3af class, the PSE can manage the power allocation by subtracting the powered device's class maximum value from the overall power budget. If the value exceeds the available budget, power is not applied to the port. If the power is within the budget, power can be applied. The semantics of managing power budgets are vendor implementation specific.

From this excellent White Paper;

http://www.cisco.com/en/US/netsol/ns340/ns394/ns147/ns412/networking_solutions_white_paper09186a008026641c.shtml#wp43581

This doc is also very good;

Power over Ethernet (PoE) Power Requirements FAQ

http://www.cisco.com/en/US/products/hw/phones/ps379/products_qanda_item09186a00808996f3.shtml

Hope this helps!

Rob

Cisco Employee

Re: TFTP server on IP Phone (branch office)

Ah, thanks for the assist here Rob! Great info, as always.

Regards,

Michael.

Cisco Employee

Re: TFTP server on IP Phone (branch office)

Hi Abhijit,

By Cisco inline power, I am referring to Cisco Prestandard PoE. The Cisco Prestandard PoE was Cisco's innovation for supplying power to IP phones when these IP phones were first introduced. A few years later the IEEE formalized a standard method (802.3af) for doing this in order to provide interoperability between different vendors' powered devices and power source equipment.

After the 802.3af PoE standard was formalized, Cisco delivered switches that could support both the Cisco prestandard method of supplying power over ethernet, as well as the 802.3af PoE method. Several switch models today support both methods.

Because the legacy phones such as the 7940s were manufactured before the standard was formalized in 2003, they only support Cisco Prestandard PoE method and not the 802.3af PoE method. The 7941's on the other hand has the smarts to be able use either methods.

So to answer your question, the 7941G still needs to connected to a PoE switch for it to get power. It will work on a legacy switch that only supports Cisco Prestandard PoE, and it will also work on a switch that supports the 802.3af PoE method.

Several other TNP-based phone models also support both methods, and a few newer ones support only the 802.3af standard PoE method.

You can find more information on PoE on CCO. Here are a few good links:

http://www.cisco.com/en/US/products/hw/phones/ps379/products_qanda_item09186a00808996f3.shtml

http://www.cisco.com/en/US/products/hw/switches/ps5528/products_white_paper09186a008026641c.shtml

http://newsroom.cisco.com/dlls/2004/prod_021704.html

Hope this helps.

Thanks,

Michael.

Hall of Fame Super Red

Re: TFTP server on IP Phone (branch office)

Hi Michael,

Good stuff my friend! +5 points for this plus all the other valued info you share here.

Rock On!

Rob

Community Member

Re: TFTP server on IP Phone (branch office)

Michael / Rob,

Thanks for all the info. Both of you have a nice weekend..

Take care,

Abhijit.

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