Multiple buffers for removing unwanted header information...

Details Multiple buffers for removing unwanted header information... Multiple buffers for removing unwanted header information...

2001-05-03

2004-05-11

Gaffin, Jeffrey (Department: 2182)

Electrical computers and digital data processing systems: input/

Input/output data processing

Peripheral adapting

C710S007000, C710S033000, C710S052000, C710S053000, C710S056000

Reexamination Certificate

active

06735649

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to received data packets in a network, and more particularly to the removing unwanted header information from received data packets in the network.
BACKGROUND OF THE INVENTION
Home networks are becoming more common and desirable for connecting computers within a home. One type of home network is the home phone line network which uses telephone lines typically installed in residence homes for communication between computers in the home. The Home Phone Line Networking Alliance (HPNA) has published a specification to standardize the behavior of home phone line networks.
FIG. 1
illustrates the frame format according to the HPNA standard version 2.0. The frame includes a known 64 symbol preamble
102
and frame control bits
104
. The frame control bits
104
include information concerning the modulation format and other miscellaneous control information, such as cyclical redundancy check (CRC) bits. The frame also includes a six-byte destination address
106
, a six-byte source address
108
, an eight-byte limited automatic repeat request (LARQ)
110
, a four-byte Q Tag
112
, and a two-byte length/type information
114
. The LARQ
110
conveys link layer priority information and provides a negative acknowledgment protocol to increase the speed of frame retransmission. The Q Tag
112
contains information which may be used to prioritize data frames. The preamble
102
through the Q Tag
112
comprise the “header” of the frame. The remainder of the frame comprise the data
116
, which can be between 46 to 1500 bytes. The data
116
is followed by four bytes of frame check sequence (FCS)
118
, which is used to check for errors in the frame. A frame need not have both the LARQ
110
and the Q Tag
112
. The frame may have the LARQ
110
without the Q Tag
112
, the Q Tag
112
without the LARQ
110
, or neither the LARQ
110
nor the Q Tag
112
.
FIG. 2
illustrates a typical hardware-software interface for a home phone line network. The interface comprises a HPNA-compatible network interface controller (NIC)
206
which receives frames from a phone line. The NIC
206
sends the frame to a HPNA-compatible driver software
204
which is typically on a host computer. The driver software
204
then sends the frame to an upper layer software
202
, such as the Network Driver Interface Specification (NDIS).
However, the upper layer
202
may not understand the LARQ
110
and/or the Q Tag
112
and erroneously see the frame as invalid. Thus, before the driver software
204
passes the frame to the upper layer software
202
, the LARQ
110
and the Q Tag
112
must be removed from the frame.
Conventionally, when the NIC
206
forwards a frame, the frame is stored in a single buffer in the upper layer
202
. Typically, to remove the LARQ
110
and the Q Tag
112
from the frame, all of the bytes before and after the LARQ
110
and Q Tag
112
are copied to a separate buffer without gaps between the bytes. However, copying all of these bytes wastes valuable processor cycles and adds unwanted latency to the packet receive process.
Accordingly, there exists a need for an improved method and system for removing unwanted header information from a frame in a network. The present invention addresses such a need.
SUMMARY OF THE INVENTION
A method for removing unwanted header information from a frame in a network is disclosed. It includes: storing beginning bytes of the frame in a first buffer and remaining bytes in a second buffer, where a size of the first buffer is smaller than the second buffer; determining the unwanted header information is stored in the first buffer; copying bytes of the frame after the unwanted header information which are stored in the first buffer over the unwanted header information; reporting a number of bytes of the frame stored in the first buffer to be retrieved; and retrieving the reported number of bytes of the frame stored in the first buffer and the bytes of the frame stored in the second buffer. The copying of bytes occur exclusively in the first buffer. Thus, removing the unwanted header information requires fewer processor cycles and minimizes latency in the packet receive process.


REFERENCES:
patent: 5881242 (1999-03-01), Ku et al.
patent: 0574140 (1993-12-01), None
Jason Trachewsky. “Attaining Fast, Scaleable Home Networks,”CommsDesign—An EE Times Community, via Internet at www.commsdesign.com/design_center/homenetworking/OEG20010221S0081, Mar. 2001, pp. 1-11.
Khiem Le et al. “Adaptive Header ComprEssion (ACE) for Real-Time Multimedia,”Nokia Research Center, Mar. 2000, pp. 1-38.

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