Project Objective: To model a system that will transport a RTP packet stream over ATM Adaptation Layer 5.
Real-Time Transport Protocol (RTP) is an Internet protocol used for transmitting real-time data such as audio and video. It typically runs on top of the User Datagram Protocol (UDP) protocol, although the specification is general enough to support other transport protocols. UDP runs on top of IP networks, offering a direct way to send and receive datagrams over that network.
The Type 5 ATM adaptation layer (AAL) enhances the services provided by ATM, participating in the segmentation of data into 48-byte frames. The breakdown of the AAL type 5 framework consists of a common part and a service specific convergence sublayer, which may be defined to support specific user services. The adaptation layer supports the non-assured transmission of user data frames: it assumes that error recovery is provided by higher layers.
In this project, we propose to utilize the network modeling application Opnet Modeler 8.0 to model an RTP over ATM network. The network will initially compose of six unique nodes:
Our network will begin as a simplex connection, sending packets from Node (1) to (2) to (3) ... to Node (6). As our project progresses, the functionality of the RTP/UDP/IPv4 header compressor and decompressor will be joined into a single node type, as will the functionality of the RTP-AAL5 compressor and AAL5-RTP decompressor. Similarly, a single node type will generate and sink RTP packets. At this point, a duplex connection would consist of the following nodes:
The compression of RTP/UDP/IPv4 headers will follow the algorithm described in RFC2508 [2]. The packet converter algorithm adheres to the ideas written in the Encapsulation of Real-Time Data Including RTP Streams over ATM [3].
Time-permitting, we will also add a process in the RTP/AAL5 packet de/compressor to detect whether the incoming packets contain compressed or uncompressed RTP/UDP/IP headers. Uncompressed-header packets will then be allowed and transmitted over ATM in a similar fashion as described above.
Our purpose in choosing to do a project on RTP over ATM is due the team members' interest of both RTP and ATM standards and protocols.
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