Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-10-02
2002-10-29
Nguyen, Chau (Department: 2663)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S394000, C370S401000, C370S412000
Reexamination Certificate
active
06473425
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a mechanism for dispatching packets via a telecommunications network and to a network sender or router station, or node, incorporating such a mechanism.
The invention finds particular application to transmission of TCP information via an inter-or intra-network operating under an Internet Protocol.
FIG. 1
is a schematic representation of an instance of an Inter- or Intra-net with a router
10
being provided in the path between a source
12
and a destination
14
. Between the source
12
(or sender node) and the router node
10
, a net
16
is shown and between the router node
10
and the destination node
14
a further net
18
is shown. In practice, the net
16
and the net
18
can be one and the same and the router
10
effectively forms a “staging post” between the source
12
and the destination
14
. In the following, reference is made to a dispatch mechanism. It should be appreciated that the dispatch mechanism could, in the present context, equally form part of the source
12
, as opposed to being a separate “staging post” as illustrated in FIG.
1
.
FIG. 2
is a schematic representation of the configuration of a station for a router
10
or source or destination
12
,
14
. These stations can be implemented using any appropriate technology. However, as illustrated in
FIG. 2
, the station is implemented by a server computer
20
comprising a system unit
22
, optionally with a display
38
, keyboard
40
and other input devices
42
. It should be noted that the router
10
need not include a keyboard, display, etc.
FIG. 2A
is a schematic block representation of aspects of the contents of the system unit
22
. As illustrated in
FIG. 2A
, the system unit includes a processor
28
, memory
30
, disk drives
24
and
26
, and a communications adaptor
32
for connection to one or more telecommunications lines
34
for connection to the telecommunications network
16
/
18
. As illustrated in
FIG. 2A
, the components of the system unit are connected via a bus arrangement
36
. It will be appreciated that FIGS.
2
/
2
A are a general schematic representation of one possible configuration for a server computer for forming a router or sender or destination station and that many alternative configurations could be provided.
Conceptually, the Internet provides three levels of services. At the lowest level, a connectionless delivery system provides a foundation on which everything rests. At the next level, a reliable transport service provides a high level platform. At the third level, application services are provided which rely on the reliable transport service.
A fundamental Internet service consists of an unreliable, best-effort, connectionless, packet delivery system. The service is described as being “unreliable” because delivery is not guaranteed. A packet may be lost, duplicated, or delivered out of order, but the Internet will not detect such conditions, nor will it inform the sender or receiver. The service is described as being “connectionless” because each packet is treated independently from all others. A sequence of packets sent from one machine to another may travel over different paths, or some may be lost while others are delivered. The service may be described as “best-effort” because the Internet makes an earnest attempt to deliver packets.
The protocol that defines the unreliable, connectionless, delivery mechanism is called the “Internet Protocol”, and is usually referred to by its initials IP. IP defines the formal specification of data formats, including a basic unit of data transfer and the exact format of all data passing across the Internet. IP also includes rules which specify how packets should be processed and how errors should be handled. In particular, IP embodies the idea of unreliable delivery and packet routing.
Further details of aspects of the Internet and TCP/IP protocols may be found, for example, in the following U.S. Pat. Nos. 5,293,379; 5,307,347; 5,307,413; 5,309,437; 5,351,237; and 5,535,199.
The basic unit of data transfer via the IP is termed an “Internet datagram”, or alternative “IP datagram”, or simply “datagram”. A datagram comprises header and data areas, and source and destination addresses. There is no fixed size for a datagram. Bearing this in mind, and also the physical constraints of the underlying hardware services on which the Internet is based, it is necessary to divide the datagram into portions called “fragments”.
FIG. 5A
illustrates the format of an Internet datagram. The same format is used for a fragment of a datagram.
The 4 bit version field (VERS) specifies the IP protocol version and is used to ensure that all of the nodes along the path of the datagram agree on the format.
The LEN field gives the datagram header length measured in 32 bit words. The TOTAL LENGTH field gives the length of the IP datagram measured in octets including the length of the header and data.
The SERVICE TYPE field contains handling details for the datagram.
Three fields in the datagram header, IDENT, FLAGS, and FRAGMENT OFFSET, control fragmentation and reassembly of datagrams. The field IDENT contains a unique identifier that identifies the datagram.
In the FLAGS field, a first bit specifies whether the datagram may be fragmented, and a second bit indicates whether this is the last fragment in the datagram. The FRAGMENT OFFSET field specifies the offset of this fragment in the original datagram, measured in units of 8 octets, starting at offset zero.
As each fragment has the same basic header format as a complete datagram, the combination of the FLAGS and FRAGMENT OFFSET fields are used to indicate that the headers relate to fragments, and to indicate the position of the fragment within the original datagram. The FRAGMENT OFFSET field identifies the position within the datagram, and the second of the FLAGS bits mentioned above (which is sometimes called the MORE FRAGMENTS flag) is used to indicate whether there are any more fragments in the datagram, or conversely that the fragment concerned is the last fragment of the datagram.
The field PROTO is a form of type field. The HEADER CHECK SUM figure ensures integrity of header values.
SOURCE IP ADDRESS and DESTINATION IP ADDRESS contain 32 bit Internet addresses of the datagram's sender and intended recipient. The OPTIONS field and the PADDING field are optional in the datagram. The field labelled DATA represents the beginning of the data field.
As mentioned above, above the IP layer of the Internet protocol structure one service which is provided is a reliable transport service which is typically called the “reliable stream transport service”, defined by the Transmission Control Protocol (TCP). Although TCP is provided over the Internet, it is in fact an independent general purpose protocol which can also be used with other delivery systems. TCP makes very few assumptions regarding the underlying network, and it can also be used over a single network like Ethernet, as well as over a complex Internet, or Intranet.
TCP provides a reliable stream delivery service which can be contrasted with the unreliable datagram protocol (UDP) which is also provided over the Internet. Whereas UDP provides an unreliable delivery service because delivery is not guaranteed, TCP provides a more complex structure which does ensure reliable delivery in the form of a stream.
UDP provides unreliable packet delivering, whereby packets may be lost or destroyed when transmission errors interfere with data, when network hardware fails, or when networks become too heavily loaded to accommodate the load presented. TCP on the other hand, operates by providing delivery by means of a stream of bits, divided into eight-bit octets or bytes.
Given that the underlying Internet protocol is unreliable, TCP transmissions operate in accordance with a technique known as positive acknowledgement with retransmission. The technique requires a recipient to communicate with the source, sending back an acknowledgement message every time it receives data. The sender keeps a
Bancilhon Herve L
Bellaton Gilles
Finnegan Henderson Farabow Garrett & Dunner LLP
Hyun Soon-Dong
Nguyen Chau
LandOfFree
Mechanism for dispatching packets via a telecommunications... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mechanism for dispatching packets via a telecommunications..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mechanism for dispatching packets via a telecommunications... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2965139