Error detection/correction and fault detection/recovery – Pulse or data error handling – Error/fault detection technique
Reexamination Certificate
2001-03-27
2004-05-04
Decady, Albert (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Error/fault detection technique
C370S474000
Reexamination Certificate
active
06732329
ABSTRACT:
FIELD
Embodiments of the present invention relate to communication networks, and more particularly, to an apparatus and method for efficiently providing header checksums for data packets.
BACKGROUND
FIG. 1
abstracts a communication network, in which node A
102
communicates with node B
104
by sending and receiving data frames. Node A sends a data frame to node B by sending a data frame to router
110
via physical network
106
, whereupon router
110
routes the data frame to node B via physical network
108
. For simplicity,
FIG. 1
illustrates only two nodes and one router communicating via two physical networks, but in practice, an Internet comprises many physical networks, routers, nodes, switches, and other devices. Nodes A and B may be, for example, computers, routers, or other types of processors.
The layered concept of communication is illustrated in
FIG. 1
, where layers
102
a
,
102
t
,
102
i
, and
102
n
provide, respectively, application, transport, internet, and network interface functions for node A; layers
104
a
,
104
t
,
104
i
, and
104
n
provide, respectively, application, transport, internet, and network interface functions for node B; and layers
110
i
and
110
n
provide, respectively, internet and network interface functions for router
110
. The network interface layer may comprise a data link layer and a PHY layer. The transport layer may implement TCP (Transmission Control Protocol) and the Internet layer may implement IP (Internet Protocol). Various layers, or portions of the layers, may be implemented in hardware or software.
Application layers
102
a
and
104
a
are software layers running application programs that may be the source or destination of transmitted data. The transport, internet, and network interface layers pass packets between them. The layered concept employs encapsulation. The transport layer receives data from the application layer, and creates a packet, sometimes called a transport protocol packet. The internet layer encapsulates the transport protocol packet into a larger packet, sometimes called an IP datagram (assuming the internet layer employs IP). The network interface layer encapsulates the IP datagram into a network-specific packet, sometimes called a frame, for transmission over a physical network. See, for example,
Internetworking with TCP/IP
, Douglas E. Corner, Prentice Hall, for a more detailed discussion of communication networks and the layered concept. For simplicity, frames and datagrams may be referred to as simply packets.
A simplified illustration of a packet is given in FIG.
2
. Packet
202
comprises payload
204
and header
206
. Header
206
usually comprises a number of fields, but for simplicity, only checksum field
208
is shown in
FIG. 2. A
checksum is an integer value, usually computed from a sequence of octets by treating them as integers and computing their sum. Many TCP/IP protocols use a 16-bit checksum computed by one's complement arithmetic. A header checksum may sum over all octets in a header, some of the octets, or all the octets plus additional octets outside the header field. A checksum is used to detect errors. Upon reception of a packet, a checksum on the received packet is performed and compared with the received value of the checksum. If the received and computed checksums do not match, then an error may be indicated.
Checksums are ubiquitous in data packet communications, and efficiently computing checksums is of practical utility and interest.
REFERENCES:
patent: 5050166 (1991-09-01), Cantoni et al.
patent: 5701316 (1997-12-01), Alferness et al.
patent: 5745502 (1998-04-01), Khayrallah et al.
patent: 5935268 (1999-08-01), Weaver
patent: 5996113 (1999-11-01), Korn et al.
patent: 6341129 (2002-01-01), Schroeder et al.
patent: 2003/0061561 (2003-03-01), Rifaat et al.
patent: 465006 (1992-01-01), None
De'cady Albert
Dooley Matthew C.
Intel Corporation
Kalson Seth Z.
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