Electrical computers and digital processing systems: interprogra – Application program interface
Reexamination Certificate
2002-01-17
2004-03-23
Courtenay, III, St. John (Department: 2126)
Electrical computers and digital processing systems: interprogra
Application program interface
C709S230000
Reexamination Certificate
active
06711740
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to implementation of text-based applications programming interfaces that provide data compression for communication of protocols between two devices via a bandwidth-limited channel.
2. Description of the Related Art
Networking communications is based on establishment of a communications protocol between two devices for transfer of information via a communications channel. The communications protocol established between the two devices enables these two devices to optimize communication based on the characteristics of the communications channel, where a receiver can recover data transmitted by the transmitter. As illustrated by the Open Systems Interconnect (OSI) reference model, devices typically are implemented utilizing several “layers” (i.e., “levels”) of communications protocols, where each communication protocol layer is configured for executing a corresponding communication protocol based on a corresponding prescribed set of commands. Such layering of prescribed communications protocols has enabled communications of different application processes across a common transmission medium. The commands for a given communication protocol may be collectively referred to as an applications programming interface (APIs).
Different types of APIs have been defined for different communications protocols. One type of API is a binary API, which has the advantage of providing a precise and compressed interface.
FIG. 1A
is a diagram illustrating a conventional binary protocol, where a “packet”
10
generated according to a specified protocol interface includes a first 1-bit field
12
a
, followed by a second 3-bit field
12
b
, followed by a third 4-bit field
12
c
. The binary protocol used to generate the packet
10
provides a precise interface in that the location of each information element
12
is well defined. The binary protocol used to generate the packet
10
also provides a relatively high compression level, enabling three information elements
12
a
,
12
b
, and
12
c
to share a single data byte
14
. An example of a binary protocol is the Ethernet (IEEE 802.3) protocol.
Binary interfaces suffer from the disadvantage of a lack of flexibility and a lack of readability by a programmer. In particular, the information element
12
a
composed of a single bit allows only two states; hence, a desire to add a third state to the information element
12
a
would require either a complete redefinition of the byte
14
, or addition of a second byte
16
to accommodate the added state.
Another popular format for APIs are ASCII (text) based interfaces, illustrated in FIG.
1
B. Exemplary text-based interfaces include POP3, SMTP, HTTP, HTML, XML, and SIP. As illustrated in
FIG. 1B
, a text-based document
20
includes a tag
22
specifying prescribed attributes
24
having specified values
26
. The structure of the document
20
enables data to be arranged in any order, and enables different operations to be specified based on adding tags. The tags may be have predetermined attributes such as found with HTML, or the tags may have extensible attributes defined by referenced document type descriptors (DTDs) as found in XML.
Hence, text-based APIs provide flexibility and extensibility for future applications. However, text-based APIs require a substantially larger data size (i.e., a larger number of bytes) to store the same information as otherwise required for a binary API; in particular, several bytes are required for transfer of the text information, often resulting in a size expansion of 20 to 1 compared to binary APIs. The larger data byte requirements for text-based APIs significantly limit the ability to use text-based APIs via bandwidth-limited channels, for example wireless data channels.
One approach to reduce the data size of information involves link layer compression, for example V.42 is compression as utilized in modems and wireless devices. The V.42 compression is a general purpose compression algorithm that is applied “transparently” (i.e., independent of higher layer protocol operations) to all data traffic that flows across the communication channel. The V.42 compression algorithm dynamically builds a “code book” of symbols that are relevant to all the protocols (i.e., APIs) that it transports during a communication session. In particular, the V.42 compression algorithm builds the code book as the data stream is compressed; hence, the V.42 compression algorithm must communicate the code book in its entirety to its peer on the communication link to enable the data stream to be decompressed. Consequently, the necessity of sending a new code book for each communication session results in a loss of available bandwidth for the protocol information.
Another problem associated with implementation of APIs in a device involves the memory consumption for storage of the respective sets of executable source code. In particular, an API typically is implemented by loading a unique set of executable source code for the API into the device. For example, if a device supports an HTTP service, a Telnet service, an FTP service and a Voice Gateway service, where each service utilizes a different corresponding protocol and a corresponding communications port, then each service would be implemented by loading and executing a corresponding unique set of executable source code for the corresponding protocol. Hence, implementation of multiple APIs requires memory space for each of the respective sets of executable source code.
SUMMARY OF THE INVENTION
There is a need for an arrangement that enables a transmitting network device, for example a mobile wireless telephone or a base station, to establish a protocol interface with a peer network device via a communications channel, where the protocol interface is implemented using text-based applications programming interfaces and having effective compression that minimizes bandwidth utilization of the communications channel.
There also is a need for an arrangement that enables a transmitting network node to transmit, via a communications channel, compressed data for a text-based protocol and generated based on compression codes from a code book, where the transmitting network node transmits descriptors enabling a receiving network node to reconstruct the code book.
There also is a need for an arrangement that enables a transmitting network node to support multiple protocols by utilizing respective APIs implemented based on shared attributes, enabling memory requirements for execution of the APIs to be reduced.
These and other needs are attained by the present invention, where a synthetic code book is used to identify compression codes applied to API commands for generation of synthesized data. The synthetic code book is specified by code-book tags having semantics defined according to a generic code book document type definition (DTD). The API commands are based on semantics defined by a generic API DTD. The synthesized data and the code-book tags are supplied to a destination device configured for storing the generic code book DTD and the generic API DTD, enabling the destination device to synthesize a code book for recovery of the API commands from the synthesized data.
Hence, the destination device can recover the API commands from the synthesized data based on the synthesized code book, eliminating the necessity of supplying an entire code book during each communication session.
In addition, memory requirements for execution of the APIs can be reduced, based on the generic API DTD. In particular, the inventors have realized that communications protocols (e.g., HTTP, Telnet, FTP, Voice Gateway) have similar “macroscopic” (i.e., logical) properties, including a set of commands which must be selected from, a set of procedures to execute for each command, a specific set of states the protocol may encounter, etc. Hence, these similar macroscopic properties, which are shared among the different protocols, can be realized by the generic API DTDs, which serve as a “generic
Moon Billy G.
Toebes John A.
Cisco Technology Inc.
Courtenay III St. John
Turkevich Leon R.
LandOfFree
Generic code book compression for XML based application... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Generic code book compression for XML based application..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Generic code book compression for XML based application... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3221092