[cisco-bba] ppp-max-payload - PPPOE Clients rfc4638
Christoph Loibl
cl at sil.at
Fri Apr 6 09:00:20 EDT 2007
Hi Bba-Group!
I resently stumbled over the pretty new BRAS feature introduced on
the Cisco
PPP-Max-Payload
Does anyone know about CPE devices that do support the sending of
such PPP-Max-Payload tags?
The feature made it to 12.2.31-SB(2-3) release of the router software
images (Is it planned to extend the support to other releases?). The
basic functionality as far as I understand is that PPPOE clients may
send an additional TAG within their PPPoE PADI packets to allow the
BRAS to negotiate a MRU larger than 1500. As long as the connection
between the BRAS-DSLAM-CPE supports that larger frames. This should
allow the initiating CPE to send "large" (1500 IP MTU) IP packets
through the pppoe session (which normally has an overhead of 8 byte
thus reducing the ip mtu to 1492).
The configuration on the BRAS is pretty simple:
bba-group pppoe TEST
virtual-template 1
tag ppp-max-payload minimum 1400 maximum 1700
But who knows CPEs that support the "Dialer" side of this ppp-max-
payload tag (actually sending that tag - to allow the bras to
negotiate this feature)?
Regards
Christoph
--
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Ing Christoph Loibl <cl at sil.at> Senior Network Engineer
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