HPE FlexNetwork MSR Series Comware 5 Layer 2 - Wan Access Configuration Manual page 25

Step
Enable the local end to
3.
assign a DNS server IP
address to the peer.
Configuring ACCM negotiation
The escape mechanism is implemented to transparently transmit asynchronous control characters
on asynchronous links. This is to avoid payloads being treated as control characters when the
payloads contain the same characters as the control characters. The length of each asynchronous
control character is 1 byte. PPP uses the escape mechanism to map all 1-byte asynchronous control
characters into 2-byte characters. This increases the bandwidth consumed by asynchronous control
characters and as a result reduces effective payload bandwidth.
The ACCM configuration option provides a method to negotiate the use of control character
transparency on asynchronous links. The ACCM field contains 32 bits numbered 1 to 32 from left to
right. Each bit corresponds to an asynchronous control character numbered the same. If the value of
a bit is 0, the system does not escape the corresponding asynchronous control character. If the value
of a bit is 1, the system escapes the corresponding asynchronous control character by prefacing it
with a backslash (\). For example, if the value of the bit numbered 19 is 0, the asynchronous control
character numbered 19 (DC3, Control-S) will be sent without being escaped.
ACCM negotiation is implemented at the LCP negotiation phase. After ACCM negotiation is
completed, the peer escapes asynchronous control characters according to the Async Control
Character Mappings when sending packets.
By default, the ACCM field takes the value of 0x000A0000. To reduce the bandwidth consumed by
asynchronous control characters and increase effective payload bandwidth on low-rate links, set the
ACCM field to 0x0 (the system does not escape asynchronous control characters).
To configure ACCM negotiation:
Step
Enter system view.
1.
Enter interface view.
2.
Configure the ACCM value.
3.
NOTE:
ACCM negotiation applies only on asynchronous links.
Configuring ACFC negotiation
By default, in a PPP packet, the address field is fixed to 0xFF, and the control field is fixed to 0x03.
The fixed values make it easy to compress these two fields.
ACFC negotiation notifies the peer that the local end can receive packets carrying compressed
address and control fields.
ACFC negotiation is implemented at the LCP negotiation stage. After the ACFC negotiation is
completed, the device compresses the address and control fields of non-LCP packets before
sending them out, and does not add address and control fields to them, thus increasing effective
Command
ppp ipcp dns
primary-dns-address
[ secondary-dns-address ]
Command
system-view
interface interface-type
interface-number
ppp accm hex-number
14
Remarks
By default, a device does not
assign a DNS server IP address
to the peer.
The server specifies a DNS
server IP address for a client
only after receiving a request
from the client.
Remarks
N/A
N/A
Optional.
By default, the ACCM value is
0x000A0000.