ADC 3 About Packet Over SONET

ADC Telecommunications, Inc.
116 CHAPTER 7: PACKET OVER SONET ADMINISTRATION
About Packet Over SONET
Packet Over SONET enables the Cuda 12000 to transmit IP packets over
SONET links; essentially placing the IP layer over the SONET physical layer.
POS makes efficient use of bandwidth, allowing for lower packet overhead
and extremely fast transmission speeds.
The system uses point-to-point protocol (PPP) to transport IP data over
SONET point-to-point circuits, as described in RFC 2615. The IP over SONET
transmission process consists of three primary steps:
■Encapsulate the IP datagram into a PPP frame.
■Place the PPP frame into the payload portion of the SONET frame.
■Transmit the SONET frame over the point-to-point circuit.
Figure 6-1 shows the POS transport structure in relation to the OSI network
model:
Figure6-1 Packet Over SONET — Network Structure
POS administration on the Cuda 12000 involves the following:
■Administration of the physical SONET interface at layer 1, as described in
“Packet Over SONET (POS) Interface Administration,” next.
■Administration of the point-to-point protocol (PPP) used to encapsul ate
the IP data at layer 2, as described in “Configuring Point-to-Po int Protocol
(PPP)” on page137.
IP Datagram
PPP Encapsulation
SONET
Layer 3 — Network Layer
Layer 2 — Data Link Layer
Layer 1 — Physical Transport Layer