Configure Advanced interfaces settings
Digi TransPort User Guide
310
Attempt to negotiate MPPE encryption on this interface
When enabled, causes the router to attempt to negotiate Microsoft Point-to-Point Encryption
(MPPE) with the remote peer. If the remote peer is unable to negotiate MPPE, negotiations will
fail. When negotiated, the PPP instance will encrypt the PPP frames as per the MPPE
specification.
MPPE key size
The values in this drop-down list select the length (in bits) of the encryption key. The options
are:
• Auto
• 40 bits
• 56 bits
•
128 bits
Auto
indicates that the router will accept whatever the remote suggests. For the other values,
the remote must accept and request the key size specified, else the PPP negotiations will fail.
Enable MPPE stateless mode
When this checkbox is checked, the router negotiates stateless mode in which the session key
is changed after the transmission of each packet. Stateless mode may be useful for lossy links.
Note
MPPE does not provide authentication, only encryption. This is because the encryption
keys are determined by the PPP engines themselves on start-up.
Use PPP m for processing CHAP
TCP transmit buffer size n bytes
When the value in this text box is set to a non-zero value, the router uses the value to set the
size of the TCP buffer for transmitted packets. This is useful for slow and/or lossy connections
such as satellite links. Setting this buffer to a low value will prevent the amount of
unacknowledged data from getting too high. If retransmits are required, a smaller TX buffer
helps prevent retransmits flooding the connection.
