Broadcast traffic reduction in a communications network

Details Broadcast traffic reduction in a communications network Broadcast traffic reduction in a communications network

1999-06-22

2003-04-29

Nguyen, Chau (Department: 2663)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

Reexamination Certificate

active

06556575

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This invention relates generally to packet switching and in particular to a method and system of reducing broadcast packet traffic through a switching device.
BACKGROUND OF THE INVENTION
Internetworking refers to linking individual local area networks (LANs) or LAN segments together to form one integrated, seamless network. One example of internetworking LANs, in a broad sense, is the Internet in which a collection of computer networks worldwide are linked together. Repeaters, bridges, routers, gateways, and switches are devices most often used for internetworking.
The simplest internetworking device, the repeater, regenerates signals that have been attenuated and/or distorted, thus permitting the signal to be transmitted greater distances. The repeater operates at the physical layer of the Open System Interconnection (OSI) reference model.
The OSI reference model is a standard produced by the International Organization for Standardization (ISO) for worldwide communications that defines a framework for implementing communications protocols. The framework consists of seven layers. The various layers refer to software protocol levels, with each layer performing functions for the layers above it. The layers, as shown in the OSI Reference Model
100
in
FIG. 1
include an application layer
102
, a presentation layer
104
, a session layer
106
, a transport layer
108
, a network layer
110
, a data link layer
112
, and a physical layer
114
.
The application layer
102
defines program-to-program communications. The presentation layer
104
manages data representation conversions, i.e., converting from EBCDIC to ASCII. The session layer
106
is responsible for establishing and maintaining communications channels. The session layer
106
is sometimes combined with the transport layer
108
which is responsible for end-to-end integrity of data transmission. The network layer
110
defines the protocol for routing data from one node to another while the data link layer
112
is responsible for physically passing the data from one node to another. Functions such as error control, addressing, and flow control are also performed in the data link layer
112
. Finally, the physical layer
114
manages the placement of data onto and removal of data from the network media.
A bridging device typically is a two port device which connects two LANs together and forwards (or filters) data packets between the two LANs based on their destination address. The bridging device operates at the data link
112
(or media access control (MAC)) layer in the OSI reference model
100
.
A routing device is a host that is connected to more than one LAN and routes messages between them based on specific protocol rather than by packet address. In other words, while repeaters and bridging devices link together two or more LANs that use the same protocol, the routing device is used to link together two or more LANs that operate different protocols. Thus, while the repeater operates at the physical layer
114
and the bridging device operates at the data link layer
112
in the OSI reference model
100
, the routing device, which routes data between two or more LANs using one of many different protocols, operates at the network layer
110
. In other words, the routing device interconnects two or more LANs (or divides one LAN into two or more LAN segments) logically rather than physically.
Another difference between the routing device and the lower complexity repeater and bridging device is that the routing device is not transparent to other nodes on the network but is itself a host, i.e., an addressable node. A host is generally a node on a network that can be used interactively, i.e., logged into, like a computer. Each host, or node, has one or more associated addresses, including at least one fixed hardware address assigned by the device manufacturer. Most nodes also have a protocol specific address, such as an Internet protocol (IP) address, which is assigned by a network manager.
The gateway is the most complex of the internetworking devices. It operates across all seven layers of the OSI reference model
100
and provides a complete hardware and software translation between the networks it connects. The gateway thus functions to connect networks of different architectures and operating under different protocols.
A switching device, on the other hand, is a multiport device designed to increase network performance by allowing only certain traffic on the individual LANs or LAN segments attached to its ports. The switching device forwards packets between LANs based upon both their source and destination addresses. Thus, traffic is routed between only those ports that require it. Each port on the switching device may be connected to a single computer or to a concentrator, or hub, which allows the bandwidth of the port to be shared among several users.
It is very common in network topology design to have a central file server or default router stationed off a single port on the switching device. Inter-host traffic reduction is obtained on the switching device through the use of virtual LANs (VLANs), i.e., subdividing the hosts connected to the switching device into individual sub-nets.
The switching device may be a managed switch. Switches are commonly managed by simple network management protocol (SNMP) applications. These SNMP applications communicate with the managed devices using a communications protocol, such as internet protocol (IP). All managed devices, including the switch, thus have one or more IP addresses. Workgroups, which include clients, servers, or clients and servers, appear as one or more IP sub-nets. A sub-net is a group of devices whose IP addresses have the same prefix. A device which belongs to more than one sub-net will thus have multiple IP addresses, i.e., one for each sub-net.
An IP address includes a network address component and a host address component. The sub-net to which a device belongs is identified using a sub-net mask. The sub-net mask is the network address plus the bit or bits reserved for identifying the sub-net. The sub-net mask is called a mask in that by performing a bitwise AND operation on the IP address and the sub-net mask, the sub-net to which the IP address belongs is identified.
By dividing a network into sub-nets, traffic reduction between devices on different sub-nets is achieved. A traffic problem persists with the server and router, however, in that in order to serve multiple hosts, or route between VLANs or IP sub-nets, the server and router ports must see all broadcast traffic from all hosts. Although this problem can be alleviated by substituting a router in place of the switching device, this is not a preferred solution. First, router cost per port is significantly greater than switch cost per port. Secondly, routing devices cause increased network latencies (the amount of time required to determine if a packet should be filtered or forwarded).
There is currently no solution to the heavy broadcast traffic load to servers and routers and other similar devices stationed off a switch port.
SUMMARY OF THE INVENTION
The present invention is a method and system for processing broadcast packets in a network using a switching device which interconnects sub-portions of the network. Each network sub-portion is connected to at least one of a plurality of switch ports on the switching device. The switching device is operable to forward certain of the broadcast packets between the sub-portions of the network via the switch ports in accordance with a forwarding algorithm. Certain of the switch ports are identified as filtered ports. Packets received through one of the switch ports include a destination port identifier. If the destination port is not a filtered port, the present invention forwards the received packet in accordance with the switch forwarding algorithm. If the destination port is a filtered port, the present invention is operable to forward the received packet to a data processor. The data processor is operable to forwa

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