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DECnet IV, DECnet Plus, DNA and OpenVMS
DECnet is a protocol suite developed and supported by Digital Equipment Corporation (Digital or DEC, now part of HP). Several versions of DECnet have been released. The original DECnet allowed two directly attached minicomputers to communicate. Subsequent releases expanded the DECnet functionality by adding support for additional proprietary and standard protocols. Currently, two versions of DECnet are in wide use: DECnet Phase IV and DECnet plus (DECnet V). The DECnet now is part of the HP OpenVMS.
DECnet is developed under the framework of the Digital Network Architecture (DNA), which is a comprehensive layered network architecture that supports a large set of proprietary and standard protocols.
The DECnet Phase IV DNA is similar to the OSI architecture, which utilizes a seven layered approach. However, the Phase IV DNA is comprised of eight layers. The DECnet Phase IV DNA specifies four upper layers to provide user interaction services, network-management capabilities, file transfer, and session management. Specifically, these are referred to as the user layer, network management layer, network application layer, and session control layer.
The DECnet phase V (or DECnet Plus or DECnet/OSI) defines a layered model that implements three protocol suites: OSI, DECnet, and TCP/IP. DECnet plus conforms to the seven-layer OSI reference model and supports many of the standard OSI protocols. DECnet plus provides backward compatibility with DECnet Phase IV and supports multiple proprietary Digital protocols. DECnet plus supports functionality in the application, presentation, and session layers. The TCP/IP implementation of DECnet plus supports the lower-layer TCP/IP protocols and enables the transmission of DECnet traffic over TCP transport protocols.
Protocol Structure - DECnet in Digital Network Architecture (DNA) and OpenVMS DECnet DNA phase IV and V in the OSI model and comparison with the TCP/IP suite:
The key protocols in DECnet protocol suite:
|
Application |
NICE: Network Information an Control Exchange protocol |
|
Presentation |
DAP: Data Access Protocol |
|
|
CTERM: Command Terminal |
|
Session |
SCP: Session Control Protocol |
|
Transport |
NSP: Network Service Protocol |
|
Network |
DRP: DECnet Routing Protocol |
|
Data Link |
MOP: Maintenance Operation Protocol |
|
|
DDCMP: Digital Data Communications Message Protocol |
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Protocol ID - The Protocol ID is set to 1000.
- Version number - The Version number is set to 0001.
- Message type - The message type is the DCAP message type.
- Packet length - The total packet length is the length of the packet including the DCAP header, DCAP data and user data. The minimum size of the packet is 4, which is the length of the header.
Related Protocols
Ethernet , Token Ring , FDDI , TCP , IP , ISO-TP , Frame Relay, LAPB , HDLC , IEEE 802.2
Sponsor Source
DECnet protocols are defined by Digital Equipment Corporation (Now part of HP).
Reference
http://ftp.digital.com/pub/DEC/DECnet/PhaseIV/ : DECnet Phase IV Specifications
http://h71000.www7.hp.com/DOC/73final/6501/6501pro.HTML : DECnet-Plus for OpenVMS Introduction and User's Guide |
