ATM Adaption Layer 5 (AAL 5)
Features
- Scalable design up to 64K connections
- Packet size up to 64K bytes
- Common part convergence sublayer (CPCS) trailer generation and checking, including cyclic redundancy code, CRC-32
- Reassembly timers to detect lost cells
- AAL 0 mode support
- User-programmable loss priority and congestion indication per message
- User-programmable UU octet per message
- User-programmable virtual path identifier/virtual channel identifier (VPI/VCI) per virtual connection
- Operation administration and maintenance (OA&M) cell insertion and extraction
- Includes UTOPIA Master/Slave Level 1/2/3 as a part of the core
- Optional integration with Modelware’s Frame Relay, AAL 1, and AAL 2 cores
- Highly configurable in terms of size, functionality, and speed
Block Diagram
Figure 1 shows the block diagram for the AAL 5 core.
Figure 1. Block Diagram
 View full detail (105 KB)
Description
Modelware offers two modular products for AAL 5: Foundation and Manager. The AAL 5 Foundation core implements the Common Part of the AAL type 5, including the CPCS and the SAR in Streaming Mode. In addition, the AAL 5 Foundation core performs asynchronous transfer mode (ATM) header insertion and extraction, which are ATM layer functions. The AAL 5 Manager core includes the Foundation core and the memory management functions needed to support the AAL 5 Message Mode.
On the service access point side, both AAL 5 cores interface to the user’s circuitry through an easy-to-use packet interface. On the ATM side, the cores interface to an ATM switch through a UTOPIA interface.
The AAL 5 Foundation segmentation engine receives complete packets or bursts that are either a multiple of 48 bytes or contain an end-of-packet (EOP). Each packet or burst is associated with a VCID (or VPI/VCI). The packets or bursts are converted into ATM cells with the appropriate header and VPI/VCI fields that are read from the connection table or received directly from the user interface. For each cell that is processed, the core stores intermediate length and cyclic redundancy code values. The last cell (or both the last and prior to the last) is appended with the appropriate pad bytes and the AAL 5 trailer including the length and cyclic redundancy code fields.
The AAL 5 Foundation reassembly engine receives multiplexed ATM cells from different connections. Using the direct VCI to VCID mapping, or VPI/VCI to VCID mapping through an external content addressable memory (CAM), the VCID corresponding to each ATM cell is obtained. As each ATM cell is received for each connection, intermediate length and cyclic redundancy code values are calculated and stored. The ATM cell payload is forwarded to the user along with the VCID. When the last cell is received, the length and cyclic redundancy code values are checked and reported to the user using the receive status signals. Timers are used to detect dead connections. If a timeout occurs, the connection is closed and an error is reported using the receive status signal available on the output interface.
Table 1 lists the typical device utilization results for the megafunction.
| Table 1. Typical Device Utilization for the Megafunction |
| Device |
Speed Grade |
Utilization |
Performance
(fMAX) |
Parameter Setting |
| Logic Cells |
Embedded System Blocks (ESBs) |
| Stratix® GX |
-5 |
4,580 |
61 M4K, 2 M512 |
>170 MHz |
Active VCID=256; ATM Channels=2 |
| Cyclone® |
-6 |
4,616 |
25 |
>130 MHz |
Active VCID=32; ATM Channels=2 |
Deliverables
- Source code (for source code licenses only)
- Test bench (for source code licenses only)
- Cyclone, Stratix, Stratix GX, Stratix II netlist
- Simulation scripts
- Synthesis scripts and constraint files
- Quartus® II software constraint file
- Detailed documentation
Contact Information
For additional information, contact Modelware:
Modelware (USA)
10 West Bergen Place
Suite 105
Red Bank, NJ 07701
Tel. (732) 936-1808
Fax (732) 936-1839
E-mail: altera@modelware.com
URL: www.modelware.com
Modelware (Europe)
Kuechel str. 14
96047 Bamberg, Germany
Tel: +49 951 299-9870
Fax: +49 951 299-9872
Email: altera@modelware.com
URL: www.modelware.com
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