HP 3000 Manuals

COMMUNICATOR 3000/XL Release 1.2, Version A.20.10

NetDelivery/XL 

by Peyman Milanfar--Information Networks Division 

DESCRIPTION OF SOFTWARE 

NetDelivery/XL is a network distributed application service.  It is a
message and file delivery system for HP AdvanceNet networks.  It provides
a reliable message delivery service based on HP Network Services
(NS3000/XL), Network File Transfer (NFT), Remote Process Management
(RPM), and Network Inter-Process Communication (NetIPC). Message delivery
is achieved by queuing all messages on disc, (referred to as "spooling"
), and coordinating the inter-node communication to ensure successful
delivery of messages.

In NetDelivery/XL, the sending process (the client) sends the message to
a queue which is a disc file.  The receiving process (the server) reads
the message from the queue when it is ready.  The client refers to the
server only by its name and does not need to know the server address, the
way the service is implemented, or the time of implementation.

NetDelivery/XL is an asynchronous or background service.  It allows the
application to continue without waiting while NetDelivery/XL delivers its
messages.  The queue allows messages to build up until the server is
ready to read them.  Subsequently, messages in queues are not lost in
case of line or node failures.

The NetDelivery/XL product consists of two components.  The first is the
utility called NDUtil which is used to install, configure and monitor
NetDelivery/XL applications, and to perform diagnostics.  The other is
the set of intrinsics which can be used to develop application programs.
The following figure represents a model of the NetDelivery/XL
communications environment.


          NetDelivery Communication Model 

FUNCTIONAL DESCRIPTION 

NetDelivery/XL provides a reliable message delivery system.  It is
asynchronous and does not depend upon the receiver node being available
when the message is being sent.  Thus, the client can send the message
and continue processing the next application without waiting for the
server to pick up and process the message.

In NS3000/XL, each node is referred to by a nodename rather than by its
address.  NetDelivery/XL carries this a step further.  An application can
now send its message to a queue.  NetDelivery/XL will identify the node
on which the queue resides.  Therefore, the client need know only the
queue name and not the actual topology of the network.  The following
figure illustrates how NetDelivery/XL sends a message to a queue name on
a remote node without knowing the physical address of the node.


          NetDelivery/XL Location Transparency 

NetDelivery/XL can be configured so that the server is activated only
when a message arrives for it to act upon.  The activation of the server
is totally transparent to the client.  When a message arrives, the
Controller (NetDelivery's Dispatch Process) activates the corresponding
server which then reads and processes the message.  Servers can be
activated during periods of low activity, if necessary, and thereby
redistribute the load on the network.  The following figure illustrates
how NetDelivery/XL's Controller process automatically invokes a server
process.


          NetDelivery/XL Automatic Process Invocation 

The server can also be programmed to reply to the client after processing
the message.  The reply is sent to a replyqueue which is then processed
just like an ordinary message.

The NetDelivery/XL intrinsics are used by application-level programs
which are developed by the user.  Such programmatic interfaces designed
for customized applications provide flexibility.

The store-and-forward feature of NetDelivery/XL enables messages to be
sent without all the intermediate nodes between the client and server
being simultaneously active.

NetDelivery/XL utilizes static, incremental routing.  Incremental routing
means that each node or the route node computes the rest

of the route using the local configuration information.  Static routing
does not allow the selection of alternate routes.  Thus, when a route
fails, NetDelivery/XL will retry via the same link until it is available.

FEATURES 

NetDelivery/XL provides the following features:

 *  Reliable Delivery:  If a node is down, NetDelivery/XL will continue
    trying to deliver the message until it succeeds.

 *  Message Queues:  The client only refers to queues, not the actual
    nodes.

 *  Attached Files:  Message space is limited.  If a long message has to
    be sent or if the message already exists in a file, then this file
    can be attached to the message and sent.  NetDelivery/XL transfers
    this file using NFT.

 *  Distribution Lists:  NetDelivery/XL supports multiple destinations in
    the form of lists.  The lists contain message queues.  Clients only
    need to send the message once.

 *  Location Transparency:  The client does not have to know the specific
    configuration or the physical address of each node.  NetDelivery/XL
    will use its configuration file to translate the queue name to the
    corresponding node address.  If the configuration changes, the
    application program remains unaffected.  The network administrator
    can simply update the configuration file.

 *  Automatic Process Invocation:  NetDelivery/XL can be configured so
    that the server program is started at any convenient time or as
    messages arrive.

 *  Replies:  The server program can send a reply to the client
    acknowledging that the message has been processed.

 *  Priorities:  Priorities can be assigned to messages so that messages
    with the highest priority will be sent first.

 *  Internal Authentication:  NetDelivery/XL verifies that internal
    message traffic is between two bona fide system processes.

 *  Forwarding:  Servers can forward the message to another queue.  This
    process is transparent to the client as well as the new server.

 *  Event Scheduling:  NetDelivery/XL can control when message transfer
    actually takes place.  This feature can be used to take advantage of
    off-peak hours, and low rates during certain times.

 *  Store and Forward:  This feature enables NetDelivery/XL to send a
    message without all the intermediate nodes between the client and the
    receiver being up simultaneously.

 *  Message Logging:  The goal of message logging is to keep a permanent
    record of a message's passage through a node.  In this way, each
    message can be traced from its inception to its endpoint.

PRODUCT DEPENDENCY 

The following lists hardware and software requirements.

Hardware 

NetDelivery/XL is an application service for HP 3000 Series 9xx Precision
Architecture systems.

Software 

 *  NS3000/XL (HP36920A)
 *  MPE/XL 1.2 or later Operating System
 *  Pascal Runtime Library
 *  KSAM
 *  Native Language Support
 *  NetDelivery/XL does not support ASNP (Asynchronous Serial Network
    Link).

PRODUCT DOCUMENTATION 

For additional information, please refer to the following NetDelivery/XL
reference material:

 *  NetDelivery/XL Intrinsics Reference Manual (P/N 32349-61001)
 *  NetDelivery/XL Utility User's Guide (P/N 32349-61002)
 *  NetDelivery/XL Error Message Manual (P/N 32349-61003)

MPE/iX Communicators