AudioCodes Mediapack mp-11x, Руководство пользователя

Страница: 368 / 390

SIP User's Manual 368 Document #: LTRT-65409
MediaPack Series
You can control the activation of No-Op packets by using the
ini
file parameter
NoOpEnable. If No-Op packet transmission is activated, you can control the time interval in
which No-Op packets are sent in the case of silence (i.e., no RTP or T.38 traffic). This is
performed using the
ini
file parameter NoOpInterval. For a description of the RTP No-Op
ini
file parameters, refer to 'Networking Parameters' on page 256 .
„
RTP No-Op:
The RTP No-Op support complies with IETF’s draft-wing-avt-rtp-noop-
03.txt (titled ‘A No-Op Payload Format for RTP’). This IETF document defines a No-
Op payload format for RTP. The draft defines the RTP payload type as dynamic. You
can control the payload type with which the No-Op packets are sent. This is performed
using the RTPNoOpPayloadType
ini
parameter (refer to 'Networking Parameters' on
page 256 ). AudioCodes’ default payload type is 120.
„
T.38 No-Op:
T.38 No-Op packets are sent only while a T.38 session is activated. Sent
packets are a duplication of the previously sent frame (including duplication of the
sequence number).
Note:
Receipt of No-Op packets is always supported.
8.3 Point-to-Point Protocol over Ethernet (PPPoE)
Point-to-Point Protocol over Ethernet (PPPoE) is a method of sending the Point-to-Point
Protocol packets over an Ethernet network.
8.3.1 Point-to-Point Protocol (PPP) Overview
Point-to-Point Protocol (PPP) provides a method of transmitting data over serial point-to-
point links. The protocol defines establishing, configuring and testing the data link
connection and the network protocol.
The PPP standard describes a state machine used to establish a valid connection between
two hosts over a serial connection. There are three major stages described, helping to
establish a network layer (such as an IP) connection over the point-to-point link: LCP (Link
Configuration Protocol) Authentication and NCP (Network Control Protocol). Once the
network protocol is configured, the two hosts can communicate, sending network layer
protocol (such as IP) over the PPP connection (a small PPP header is added at the
beginning of each packet).
At the initial phase, the hosts use LCP (link configuration protocol) to negotiate for link
characteristic and parameters. Packets sent in this phase have two octets of ‘PPP header’
followed by LCP message with variable length. Various parameters and options are
negotiable at this phase, including MRU (maximum receive unit), Authentication Protocol,
and others.
Once the link is established (each side sends a ‘configure ack’ message to the other side),
the authentication phase may begin. The authentication phase is not mandatory. However,
it is negotiated in the link configuration phase. A host may ask other hosts for
authentication using Password Authentication Protocol (PAP) or Challenge Handshake
Authentication Protocol (CHAP). The PAP sends the username and password to the
remote host unencrypted.