Electrical computers and digital processing systems: multicomput – Computer conferencing – Priority based messaging
Reexamination Certificate
1999-07-02
2004-08-10
Dinh, Dung C. (Department: 2153)
Electrical computers and digital processing systems: multicomput
Computer conferencing
Priority based messaging
C709S239000, C370S236000, C713S152000
Reexamination Certificate
active
06775692
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to proxied connections. More specifically, a distributed method and apparatus for proxying a connection and reducing the overhead on such a proxied connection is disclosed.
BACKGROUND OF THE INVENTION
As the IP protocol has continued to be in widespread use, a plethora of network service appliances have evolved for the purpose of providing certain network services not included in the protocol and therefore not provided by standard IP routers. Such services include NAT, statistics gathering, load balancing, proxying, intrusion detection, and numerous other security services. In general, such service appliances must be inserted in a network at a physical location where the appliance will intercept all flows of interest for the purpose of making its service available.
FIG. 1
is a block diagram illustrating a prior art system for providing a network service. A group of clients
101
,
102
, and
103
are connected by a network
110
to a group of servers
121
,
122
,
123
, and
124
. A network service appliance
130
is physically located in the path between the clients and the servers. Network service appliance
130
provides a service by filtering packets, sending packets to specific destinations, or, in some cases, modifying the contents of packets. An example of such modification would be modifying the packet header by changing the source or destination IP address and the source or destination port number.
Network service appliance
130
provides a network service such as load balancing, caching, or security services. In providing security services, network service appliance
130
may function as a proxy, a firewall, or an intrusion detection device. For purposes of this specification, a network service appliance that acts as a load balancer will be described in detail. It should be noted that the architecture and methods described are equally applicable to a network service appliance that is functioning as one of the other above described devices.
Network service appliance
130
is physically located between the group of servers and the clients that they serve. There are several disadvantages to this arrangement. First, it is difficult to add additional network service appliances when the first network service appliance becomes overloaded because the physical connections of the network must be rerouted. Likewise, it is difficult to replace the network service appliance with a back up network service appliance when it fails. Since all packets pass through the network service appliance on the way to the servers, the failure of the network service appliance may prevent any packets from reaching the servers and any packets from being sent by the servers. Such a single point of failure is undesirable. Furthermore, as networks and internetworks have become increasingly complex, multiple services may be required for a single network and inserting a large number of network service appliances into a network in places where they can intercept all relevant packet flows may be impractical.
The servers may also be referred to as hosts and the group of servers may also be referred to as a cluster of hosts. If the group of servers has a common IP address, that IP address may be referred to as a virtual IP address (VIPA) or a cluster address. Also, it should be noted that the terms client and server are used herein in a general sense to refer to devices that generally request information or services (clients) and devices that generally provide services or information (servers). In each example given it should be noted that the roles of client and server may be reversed if desired for a particular application.
A system that addresses the scalability issues that are faced by network service appliances (load balancers, firewalls, etc.) is needed. It would be useful to distribute functions that are traditionally performed by a single network element and so that as much function as possible can be performed by multiple network elements. A method of coordinating work between the distributed functions with a minimum of overhead is needed.
Although network service appliances have facilitated the development of scalable server architectures, the problem of scaling network service appliances themselves and distributing their functionality across multiple platforms has been largely ignored. Network service appliances traditionally have been implemented on a single platform that must be physically located at a specific point in the network for its service to be provided.
For example, clustering of servers has been practiced in this manner. Clustering has achieved scalability for servers. Traditional multiprocessor systems have relatively low scalability limits due to contention for shared memory and I/O. Clustered machines, on the other hand, can scale farther in that the workload for any particular user is bound to a particular machine and far less sharing is needed. Clustering has also facilitated nondisruptive growth. When workloads grow beyond the capacity of a single machine, the traditional approach is to replace it with a larger machine or, if possible, add additional processors within the machine. In either case, this requires downtime for the entire machine. With clustering, machines can be added to the cluster without disrupting work that is executing on the other machines. When the new machine comes online, new work can start to migrate to that machine, thus reducing the load on the pre-existing machines.
Clustering has also provided load balancing among servers. Spreading users across multiple independent systems can result in wasted capacity on some systems while others are overloaded. By employing load balancing within a cluster of systems the users are spread to available systems based on the load on each system. Clustering also has been used to enable systems to be continuously available. Individual application instances or machines can fail (or be taken down for maintenance) without shutting down service to end-users. Users on the failed system reconnect and should not be aware that they are using an alternate image. Users on the other systems are completely unaffected except for the additional load caused by services provided to some portion of the users that were formerly on the failed system.
In order to take full advantage of these features, the network access must likewise be scalable and highly available. Network service appliances (load-balancing appliances being one such example) must be able to function without introducing their own scaling limitations that would restrict the throughput of the cluster. A new method of providing network services using a distributed architecture is needed to achieve this.
In many network applications, it is often desirable or necessary to prevent a user from making a connection to a first machine at one IP address that has information that the user needs and instead service the user's information request with a proxy machine at a different IP address. For example, it is often desired from a security standpoint not to allow a connection to a machine that stores sensitive information. Instead, it may be required that a connection first be made to a proxy that has various security features such as user authentication and possibly encryption. The user requests the information from the proxy and the proxy establishes a connection with the machine that is being protected and obtains the information. If the proxy determines that the user is authorized to receive the information, the proxy can then relay the information to the user that requested it. The proxy thus stands in for the machine that stores the sensitive information. The user is prevented from making a direct connection to the protected machine. Instead, the user must first request the information from the proxy and only the proxy connects with the protected machine. The protected machine is insulated from potentially dangerous outside contact.
In a proxy arrangement that is used for security, the proxy generally first id
Albert Mark
Howes Richard A.
Jordan James A.
Kersey Edward A.
LeBlanc William M.
Baker & Botts L.L.P.
Cisco Technology Inc.
Dinh Dung C.
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