Multiplex communications – Pathfinding or routing – Store and forward
Reexamination Certificate
1999-05-14
2004-09-07
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Store and forward
C370S428000
Reexamination Certificate
active
06788701
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a communication system (“network”) and, more particularly, to a network that employs a modular form of switch which operates to quickly route data among nodes of the network. The switch has the awareness of its position relative to other switches or nodes within the network. The switch may include buffers and decoders which wrap the internet protocol (“IP”) identification addresses through a series of fast read operations, or simply pass the wrapped IP address through the network depending on whether the switch is configured as an end switch, an intermediate switch or a pass-through switch
2. Description of the Related Art
A communication network is generally regarded as an interconnected set of subnetworks or subnets. The network can extend over localized subnets as an intranet, or can extend globally as an internet between one or more intranets. A communication network can therefore forward data within a localized network between termination devices extending to almost anywhere around the world. The termination devices include any data entry/retrieval system (e.g., telephone or computer), and a network includes a local and/or global interconnection of termination devices configured on one or more subnets.
The basic underpinnings of network operation is the various protocols used to communicate between termination devices. A popular foundation for those protocols is the Open System Interconnect (“OSI”) model. Using that model or a derivative thereof, protocols can be developed which work in concert with each other. A popular communication protocol includes the Transmission Control Protocol (“TCP”) and the Internet Protocol (“IP”). Protocols such as TCP/IP determine how the termination devices will communicate with each other over a network configured with or without internet connection.
Many popular protocols including TCP/IP deliver data across the network in the form of a packet. Each packet of a particular message may be sent across different routes of the network at the same time and then reassembled at the proper termination device. In order to ensure the packets are properly received, certain layers of the OSI protocol stack will wrap the data before the packet is sent across the network. For example, TCP can divide data into segments which are then placed into, for example, IP datagrams having a header which includes the IP address of the originating and receiving termination devices. The IP datagram and header is, therefore, a wrapped IP which gets further wrapped when transferring the IP wrapper from the network layer to the data link and physical layers. For example, the IP datagram can be further wrapped using a Point-to-Point Protocol (“PPP”), a popular such protocol being that which follows the Ethernet specification at the physical layer. Thus, it is not until the IP has been wrapped possibly several times will be TCP be forwarded across the network.
Coupled between subnets of a network are various classes of devices, including bridges, routers, and switches. Bridges and switches for the most part operate primarily in hardware and within the domain of the data link layer. Legacy routers, on the other hand, operate within the network layer and can be programmed and reconfigured to intelligently forward packets across the network according to the most optimal routing path. Although the distinction has become somewhat blurred with modern day network layer switches and bridges, it is still the primary intent that a switch and bridge be employed mostly in hardware. Based on configuration of the switch or bridge, all data packets received by a particular input port are routinely sent to any particular output port or ports. This operation can be quickly repeated each time a packet is received.
While switches are relatively fast and can send data from an input port to an output port with very little delay or lag time, switches do not have the capability to adapt to change in traffic conditions as do routers. Because routers can easily adapt to avoid traffic bottlenecks, routers employ look-up tables and fairly complex routing algorithms. Typical routers are based on a packet processor. The processor can be programmed to determine the most optimal connection between input and output ports of the router. Coupled to the processor is a memory bus and associated system memory, whereby routing tables can be stored in the system memory and are periodically fetched by the processor whenever a routing decision is to be made. Thus, when a packet is received on one port of the router, the processor will execute a look-up operation by fetching the appropriate table information from system memory. Most routing tables are dynamic, in that they constantly change as network traffic and conditions change, so that the processor can interconnect the ports in a way that is most efficient at that time. Dynamic routing tables can be built and re-built using various routing protocols, popular such protocols include Routing Information Protocol (“RIP”) and Exterior Gateway Protocol (“EGP”).
Periodically programming the routing tables may mean that one router on a network will not know the location of the physically closest router or its placement within the network. The router will simply route based on its existing routing table and the resulting look-up outcome. Such a system can be considered a non-relative or non-deterministic router topography. Non-deterministic routers tend to rely on the number of hops (i.e., the number of routers or gateways) when determining the most optimal routing path. Thus, while a router may know the number of additional routers on a given path, it does not necessarily know or have a link to the identity of those routers.
In most modem networks, a packet will travel more than 10 or 20 hops before arriving at its destination. As defined herein, a hop is equivalent to a traversal of a router or address translator. More specifically, a hop is defined as an operation that invokes a look-up or translation operation. When traveling across a network, a packet may be sent across numerous look-up or translation tables, and also through numerous switches, before arriving at its destination. It is generally recognized that transmission latency is lessened, and transmission bandwidth increased, if the number of hops is reduced. Therefore, it is desirable that the number of hops from one termination device to another termination device be minimal. This is due, in part, to the time-consumptive look-up (or address translation/modification) procedure performed by each router. Furthermore, since a particular router will not necessarily know the placement of all other routers of a network, each look-up table must include identification numbers or addresses for each of the other routers within the network - even those not within the optimal routing path. The destination address is compared against each of those identification numbers for each routing operation. If a network is quite large, the access times needed to perform a look-up from the packet processor to the system memory can be correspondingly long.
This problem is compounded with the advent of high speed networks of one gigabits per second (Gb/s) or higher. Look-up techniques needed to render forwarding decisions on rather large look-up tables drastically reduces the benefits of using high speed networks. Many termination devices use high speed physical media, such as Ethernet. Moreover, subnet loops which interconnect localized devices can use even higher speed signals such as, for example, Synchronous Optical Networks (“SONETs”).
If the IP packets enter the input port of a router more quickly than that router can process those packets, the packets are sent to an input queue. The router processes packets from the queue in the order in which they are received. If the number of packets received exceeds the capacity of the queue, packets may be lost and may need to be re-sent. If the comparison between the IP destination and the routing table t
Kapadia Viren H.
Mahalingaiah Rupaka
Chin Wellington
Conley & Rose, P.C.
Daffer Kevin L.
Dunti LLC
Jain Raj
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