# Patent

## Title
Service processing switch

## Abstract

A system and method for providing IP services. A packet is received at a line interface/network module and forwarded to a virtual routing engine The virtual routing engine determines if the packet requires processing by a virtual services engine. If the packet requires processing by the virtual services engine, the packet is routed to the virtual services engine for processing.

## Background
FIELD
The present invention relates generally to packet switching, and more particularly to a system and method for providing IP services in an integrated fashion.
RELATED FILES
This application is related to co-pending U.S. patent application Ser. No. 10/163,162 entitled “System and Method for Hierarchical Metering in a Virtual router Based Network Switch,” filed concurrently herewith, to co-pending U.S. patent application Ser. No. 10/163,261 entitled “Network Packet Steering,” filed concurrently herewith, to copending U.S. patent application Ser. No. 10/163,073 entitled “Methods and Systems for a Distributed Provider Edge,” filed concurrently herewith, to co-pending U.S. patent application Ser. No. 10/163,071 entitled “SYSTEM AND METHOD FOR CONTROLLING ROUTING IN A VIRTUAL ROUTER SYSTEM,” filed concurrently herewith, and to co-pending U.S. patent application Ser. No. 10/163,079 entitled “System and Method for Routing Traffic through a Virtual Router-Based Network Switch”, filed concurrently herewith, all of which are assigned to the same assignee as the present application and all of which are incorporated herein by reference.
COPYRIGHT NOTICE/PERMISSION
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to the software and data as described below and in the drawings hereto: Copyright © 2002, CoSine Communications, Inc. All Rights Reserved.
BACKGROUND
Internet or WAN service providers (SPs) operate in a crowded marketplace where cost effectiveness is critical. Cost control is, however, difficult. At present internetwork bandwidth is a commodity item with extremely tight margins. If the SP wishes to provide additional value-added services such as firewalls, the SP must install and configure expensive Customer Premises Equipment (CPE) at subscriber locations. Problems that arise often require a trip by a service technician to the subscriber's location. It can be difficult to add new services.
This model of value-added service delivery creates an expensive up-front capital investment, as well as significant operational expenses that are associated with onsite installation and management of thousands of distributed devices. The results are service delivery delays, increased customer start-up costs and/or thinner service provider margins.
Service providers need a way of escape from commoditized bandwidth offerings and from traditional equipment-intensive service delivery architectures that drain profits.
SUMMARY
The above-mentioned shortcomings, disadvantages and problems are addressed by the present invention, which will be understood by reading and studying the following specification.
According to one aspect of the present invention, a system and method for providing IP services includes receiving a packet at a line interface/network module, forwarding the packet to a virtual routing engine and determining, at the virtual routing engine, if the packet requires processing by a virtual services engine. If the packet requires processing by the virtual services engine, routing the packet to the virtual services engine for processing.
According to another aspect of the present invention, a system and method for providing IP services includes receiving a packet at a line interface/network module, forwarding the packet to a virtual routing engine and determining, at the virtual routing engine, if the packet requires processing by an advanced security engine. If the packet requires processing by the advanced security engine, routing the packet to the advanced security engine for processing.
The present invention describes systems, clients, servers, methods, and computer-readable media of varying scope. In addition to the aspects and advantages of the present invention described in this summary, further aspects and advantages of the invention will become apparent by reference to the drawings and by reading the detailed description that follows.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a service processing switch according to one embodiment of the present invention.
FIG. 2 conceptually illustrates an example of an IP Service Delivery Platform according to one embodiment of the present invention.
FIG. 3 illustrates the architecture of an IP Service Generator (IPSG) according to one embodiment of the present invention.
FIG. 4 illustrates an exemplary master architecture of an IP Service Generator (IPSG) according to one embodiment of the present invention.
FIG. 5 is a block diagram of a flow manager according to one embodiment of the present invention.
FIG. 6 is a table illustrating various packet types and corresponding groups, Diff Serv classes, ATM classes and queues according to one embodiment of the present invention.
FIG. 7. is a table illustrating various connectivity options and corresponding form factors, total queues and total memory according to one embodiment of the present invention.
FIG. 8 is a block diagram of a Virtual Routing Engine (VRE) according to one embodiment of the present invention.
FIG. 9 is a block diagram of an Advanced Security Engine (ASE) according to one embodiment of the present invention.
FIG. 10 is a table illustrating layers of the OSI model and roughly corresponding objects of the IPNOS model.
FIG. 11 conceptually illustrates frame processing by an IP Service Generator (IPSG) according to one embodiment of the present invention.
FIG. 12 is a flow diagram illustrating a packet forwarding process in accordance with one embodiment of the present invention.



DETAILED DESCRIPTION
In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the present invention.
Some portions of the detailed descriptions which follow are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the ways used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar computing device, that manipulates and transforms data represented as physical (e.g., electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
In the Figures, the same reference number is used throughout to refer to an identical component which appears in multiple Figures. Signals and connections may be referred to by the same reference number or label, and the actual meaning will be clear from its use in the context of the description.
The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.
Operating Environment
As noted above, traditional models of value-added service delivery create an expensive up-front capital investment, as well as significant operational expenses that are associated with onsite installation and management of thousands of distributed devices. The results are service delivery delays, increased customer start-up costs and/or thinner service provider margins.
A system 2 for providing such services in a more cost-effective way is shown in FIG. 1. Instead of requiring an array of CPE at subscriber locations in order to deploy IP services, system 2 includes one or more service processing switches 10 which enable a service provider to seamlessly infuse into and deliver from their network value-added IP services that can be bundled with subscribers' access services. In the embodiment shown, each switch 10 resides in the SP's Point of Presence (POP) 12. In one embodiment, switch 10 is installed at the edge of the core 14 and communicates with core routers within core 14. In one such embodiment the connection through switch 10 to each core router is enabled through a Service Provider Virtual Router (VR), which will be described below. In some such embodiments, switch 10 will function as an MPLS Label Edger Router (LER) establishing Label Switched Paths (LSPs) running through routers such as a Juniper M40 or a Cisco 12000.
An example of an IP Service Delivery Platform 2 based on switch 10 is shown in FIG. 2. By deploying the IP Service Delivery Platform 2 of FIG. 2, SPs can overlay value-added services directly onto access offerings.
In one embodiment, switch 10 is a 26-slot, carrier-class solution that marries switching, routing, and computing resources with an open operating system, IPNOS. In one such embodiment, switch 10 leverages the architecture described in U.S. patent application Ser. No. 09/661,130, filed Sep. 13, 2000 through the use of new IP Service Generators (IPSGs) (see FIG. 3). This combination is a powerful solution that gives SPs the industry's only multi-gigabit rate solution for delivering value-added IP services over basic transport to enterprise subscribers. Additionally, the solution delivers the processing power required to scale value-added IP services to the speed of light, consolidates network equipment and reduces operational resources required for IP service delivery, enables user-level services customization and accounting without performance degradation and offers investment protection through a service processing migration path.
Service Providers can install up to 12 dual-slot IPSGs 20 in switch 10 of FIG. 3, choosing from a variety of interfaces: Gigabit, Ethernet, DS3/E3, POS and ATM. In addition, by using hardware-based routing and computing techniques such as parallel processing and pipelining, such an approach produces the highest aggregate IP services. In one such embodiment, each IPSG 20 scales to support tens of thousands of subscriber sites and a million unique ACL-based service definitions). A switch 10 fully loaded with IPSGs can scale application services across hundreds of thousands of enterprise network sites.
In one embodiment, each IPSG 20 is a self-contained subsystem with an advanced service processing architecture for delivering network-based IP services such as Virtual Private Networks (VPNs) and Managed Firewall at multi-gigabit per second rates (OC-48). The IPSG has been designed to match the capacity of Service Providers' edge transport build-outs so they can bundle value-added services seamlessly with their high-speed access services. In one embodiment, each IPSG 20 occupies two Universal slots when installed in a Service Processing Switch 10.
As noted above, the IPSG architecture produces the highest aggregate IP services processing rate in the industry by marrying hardware-based network processor capabilities with high-end computing techniques like parallel processing and pipelining. In one embodiment, an IPSG 20 optimizes performance through three application-tailored engines: a Virtual Routing Engine (VRE), a Virtual Services Engine (VSE), and an Advanced Security Engine (ASE).
The VRE enables packet classification, deep packet inspection and service customization for up to a million Access Control List (ACL)-level flows. The VSE performs parallel processing and pipelining, two high-end computing techniques that optimize network-based performance for third-party solutions such as Check Point FireWall-1® and McAfee anti-virus. The ASE rapidly accelerates encryption processing for IPSec site-to-site and dial VPNs through the use of specialized encryption hardware.
In one embodiment, each IPSG 20 is based on the same master architecture (see FIG. 4). In the example shown in FIG. 4, the architecture is centered on a 51.2 Gbps, 8-port, fully meshed, non-blocking Service Generator Fabric 22. By intelligently partitioning out the processing elements and having them all communicate via the same high performance fabric 22, a modular and scalable services delivery architecture is possible. As a result, a varying number of processing elements—specifically, VREs, VSEs and ASEs—can be combined and pre-integrated with the Service Generator Fabric 22, Line Interface/Network Modules 24 and the Midplane Interface 25 into a family of IPSGs 20. Each IPSG 20 offers the optimum mix of scalable services, internetworking functions and performance for service providers from regional SPs all the way up to global carriers. By deploying additional IPSGs 20 in a single chassis, the services and performance of switch 10 can scale for an extremely long and profitable investment.
Although the processing requirements for network access and trunk environments have many aspects in common, such as network media, packet classification, virtual routing and packet forwarding, they do have significant differences in terms of scalability, depth of packet processing, computing power requirements and network interface bandwidth. Again, by intelligently partitioning out the processing elements into application-tailored engines such as the VRE, VSE and ASE, and by distributing functions across them, the services and functional requirements of both trunk and access environments are unified in the same architecture.
In one embodiment, each IPSG 20 employs pipelining across and within all its elements—Line Interface/Network Module 24, Service Generator Fabric 22, the Midplane Interface 25, VRE, VSE and ASE. Packet processing functions in Layers 3-7 are notoriously computation and memory intensive. Switch 10 takes advantage of the fact that Layer 3 packet functions, and in particular IP forwarding, are repetitive and can be performed in dedicated hardware. The CPUs in each VRE, VSE and ASE are coupled with specialized hardware that serve to offload from the CPUs the processing of basic network functions such as routing and packet forwarding. This leaves more MIPS and memory bandwidth that can be dedicated to upper layer packet processing such as firewall, URL filtering, anti-virus, etc.
As is shown in FIG. 4, in one embodiment, each VRE includes a virtual routing processor 30, a virtual service controller 32, a CPU 34 and memory 36. Each VSE includes a virtual service controller 32, two CPUs 34 and memory 36. Each ASE includes a security manager 38 and security hardware 40 used to accelerate security services such as encryption or key generation. In one embodiment, CPU 34 is a IBM PowerPC 750CX and security hardware 40 includes the Hi/fn 7851 (an encryption accelerator chipset supporting 500 Mbps of IPSec forwarding and hardware-based compression) and the Hi/Fn 6500 (a key accelerator enabling hardware-assisted Internet Key Exchange (IKE) negotiations and public key generation.
In one embodiment, a flow manager 42 residing on Line Interface/Network Module 24 and Midplane Interface 25 load balances service requests to the optimal VSE and VRE and supports robust priority/Weighted Round Robin (WRR) queuing capabilities. Virtual Routing Processor 30 provides hardware-assist capabilities for IP forwarding, MultiProtocol Label Switching (MPLS), Network Address Translation (NAT), Differentiated Services (DiffServ), statistics gathering, metering and marking. Virtual Service Controller 32 supports parallel processing and pipelining for optimum deep packet inspection and for third-party application computing. Security Manager 38 load balances and monitors IPSec sessions across a pool of four Hi/fn 7851 encryption chips for the highest capacity VPN processing possible.
In one embodiment, in order to achieve gigabit wire-speed packet data transfers from a physical port through the system and back out to another physical port and vice versa, all the system elements along the packet datapath throughout IPSG 20 are designed as full-duplex, high-bandwidth streaming interfaces. There is no packet data path bottleneck such as PCI or other peripheral 10 interfaces. Using a full-duplex datapath of 32 bits and a minimum interface clock speed at 100 MHz, there is ample bandwidth headroom designed in to scale packet throughput to OC-48/STM-16 (2.4 Gbps) in each direction throughout the IPSG. Ample buffer size and the use of single-stage buffering techniques along the packet datapaths help absorb burstiness in IP traffic, as well as keeping a low packet loss ratio.
In one embodiment, flow manager 26 provides the following functions: wire-speed Layer 2 packet classification, wire-speed ingress packet flow direction, wire-speed egress priority queue-based congestion avoidance and bandwidth control and 50 ms intra-blade Automatic Protect Switching (APS) support for POS and ATM interfaces.
In one such embodiment, as is shown in FIG. 5, Flow Manager 26 consists of two parts: an ingress flow director 50 and an egress flow controller 54.
Layer 2 and 3 packet header parsing and error checking is performed on the fly as the packet enters Flow Manager 26 from the physical port. Layer 2 parsing supports PPP (RFC 1619, 1662), MLPPP (RFC 1990), Cisco HDLC, MultiProtocol over Frame Relay (RFC 2427), PPPoE (RFC 2516), Ethernet, VLAN, and MultiProtocol over ATM (RFC 2684).
Layer 3 parsing supports IP header definition (RFC 1812) and MPLS (IETF label standard). The result of this function is to ensure the packet is free of link layer and IP/MPLS header errors, to offset into the packet where the Layer 3 header begins and to determine what the Layer 3 protocol is (IP/MPLS/IS-IS). All this information is written into a system control header that Flow Manager 26 later uses to encapsulate the original packet.
Using a wire-speed table lookup mechanism, an ingress flow director within flow manager 26 assists traffic distribution by directing each incoming packet to one of several destination engines. The ingress flow director parses the Layer 2 header of each packet and extracts information to address a programmable SRAM-based lookup table 52. The extracted information is the packet's logical interface, which is associated with a Virtual Router (VR) in the Service Generator that contains the destination engine ID.
Using the lookup table result, Flow Manager 26 constructs an internal control header and prepends it to the incoming packet and sends the packet to Service Generator Fabric 22. Service Generator Fabric 22 looks at the destination field of the control header and determines to which of its client engines the packet should be sent. Software is responsible for initializing and updating the lookup table. Software gets information about the load of each engine by monitoring its internal states and packet statistics collected by the hardware circuits across engines. Programming an entry in the table is in the form of software writing an in-band high priority Programmed IO (PIO) message from an engine through Service Generator Fabric 22 into Flow Manager 26.
In one embodiment, hardware-assisted QoS mechanisms are distributed throughout the entire IPSG 20. In one such embodiment, egress flow controller 54 is responsible for priority queuing with congestion control using the WRED algorithm, as well as custom queue-based scheduling using a four-priority WRR algorithm. There are four different Priority Groups, each with absolute priority over subsequent groups (i.e., groups with a higher number). Group 4 has five queues and WRR is performed among those five queues to determine which queue is serviced when Group 4 is serviced. For the last four queues of Group 4, the weight per queue is a customer-configurable parameter.
The IPSG supports three levels of QoS: EF, AF and BE. EF provides premium-expedited service with low jitter and low delay. There are two types EF traffic: EF guaranteed and EF regular. EF guaranteed can be used by high priority traffic such as system network control and IP-based voice services. EF regular is lower priority than EF guaranteed, though still higher priority than all AF and BE traffic. AF traffic is higher priority than BE. Within AF, there are four subclasses: AF1, AF2, AF3 and AF4. These subclasses and BE are differentiated by weighted scheduling factors. A representative default priority queue QoS mapping is shown in FIG. 6.
In one embodiment, there are two different types of Line Interface/Network Modules in the IPSG: those with fixed-sized queues and those with variable-sized queues. Fixed-sized queue Line Interface/Network Modules have a total of eight queues with 256 KB per queue, all the queues sharing a 2 MB shadow memory SRAM. The queues are shared across all the ports of the interface.
The variable-sized queue Line Interface/Network Modules introduce the concept of linking buffers together to dynamically allocate different sized queues. There are up to 8,000 channels per interface (the number of channels will change depending on the interface selected). Each of these channels has eight priority levels that are mapped to eight separate queues for each channel, resulting in the 64,000 queues. Each queue created is actually a link of 1 Kbyte buffers. Each buffer holds either a single packet or a partial packet but never data from two different packets. Each of the eight queues in each channel is a dynamically sized linked list. Each list can have 255 buffers of 1,024 bytes. Additionally, there exists 128 MB of external SDRAM for packet storage. The 128,000 buffers in this SDRAM are shared among the 8,192 QoS channels.
The priority queues are mapped to both IETF DiffServ traffic classes as well as ATM Forum traffic classes.
Layer 3 and 4 traffic classification, the actual determination of which egress queue a packet should be sent to, is based on DiffServ Type of Service (TOS) field marking, classification based on IP header fields, metering and rate control, which all take place in the Virtual Routing Processor on the VRE. A representative queue configuration is shown in FIG. 7.
The goal of the WRED algorithm is to randomly distribute the discarding of packets after a pre-determined level of congestion has been reached within the system. A discarded packet alerts the TCP layer that congestion is occurring in the system and that the sending side should back off its transmission of packets. Effective congestion control is time critical; in one embodiment, therefore, this function was placed completely in hardware. The alternative to WRED is known as “tail dropping”, where significant numbers of packets are discarded at once causing the TCP layer to back off in waves, and thereby delivering poor bandwidth utilization.
For Line Interfaces/Network Modules 24 with fixed-sized queues, as a packet returns to an egress interface, it will be subject to the WRED drop determination algorithm. Based on the information in the internal control header, the queue number for the packet is determined. The probability of randomly dropping the packet is proportional to the average fill-level (fullness) of that queue and its software-programmable parameters such as Minimum Threshold (Minth) and Maximum Threshold (Maxth). The parameters are unique per priority queue and per drop preference. (Drop preference is described below. Drop preference is a result of DiffServ TOS field-based traffic marking and metering. There are three drop preferences: green, yellow and red. Red has the highest drop preference.).
The drop preferences offer three drop profiles (based on three drop preferences) for each priority queue. The Minth controls the onset of the random packet dropping. This means as the queue is filled with packets, if the average fill level exceeds the Minth, random packet dropping is kicked in. The Maxth controls the onset of total packet dropping. This means that as the average queue level exceeds Maxth, all subsequent packets will be dropped. By manipulating these two thresholds, the level of fullness in a queue is controlled. If the queue is completely filled, it will block further traffic from getting into the queue.
If the packet is not dropped, it will be queued into one of the priority queues in a 2 MB of external shared memory SRAM, based on the information in the control header. The three highest priority queues are addressed in order. These queues must be empty before traffic from the fourth priority group is addressed.
A two-priority WRR packet scheduler determines from which of the five medium to lower priority queues the next packet will be sent to the outbound network. The weight for each of the five queues covers 16 Kb and is in 8 byte units. Each weight is software programmable and can be changed any time. The weight controls how many 8 byte units can be scheduled out of each queue. Once the weight is exhausted, the scheduler will move on to serve the next queue. Sometimes the weight is exhausted while the packet is still being scheduled. In this case, the remaining amount of 8 byte units will be recorded and deducted from the weight the next time the queue is served again. This is to improve bandwidth control for mixed-size packet traffic, such as TCP/IP.
It should be noted that all the data transfers in the various sub-blocks (such as WRED, WRR) are pipelined for wire speed.
For Line Interfaces/Network Modules 24 with variable-sized queues, the WRED parameters are uniquely defined on a per channel basis, not on a per queue basis. Instead of looking at the average fill level of that queue, these Line Interfaces/Network Modules 24 look at the average number of consumed buffers of the given channel. When a linked list queue in these Line Interfaces/Network Modules has consumed 255 buffers, tail dropping will occur. If the packet is not dropped, it will be queued into one of the priority queues in a 128 MB of external SDRAM memory based on the information in the control header. The three highest priority queues are addressed in the same manner as mentioned above, except that the weighting of the Priority Group 4 is based on buffers rather than bytes.
For its POS and ATM interfaces, in one embodiment IPSG 20 provides 1+1 APS, a physical failover mechanism within a Network Module 24. The 1-port OC-12 POS Line Interface doesn't support APS failover mechanism because it is limited to only one port. On the other hand, the 2-port 1+1 OC-12 POS Network Module does provide the APS capability; only one port will be active at any one time with or without APS applied. When using the 4-port OC-3 POS Line Interface or 4-port OC-3 ATM Network Module, all ports can be active simultaneously; if APS is activated in one pair of ports, the other two ports can be active resulting in three active ports in the Network Module 24. Software is responsible for detecting the conditions (receipt of SONET Physical Layer protocol K1 and K2 control bytes) that indicate a link failure.
For the ingress direction, the software programs Network Module 24 circuits to direct ingress traffic from either the primary port or the protect port across the Service Generator Fabric 22. For the egress direction, the software programs the Network Module 24 circuits to mirror egress traffic onto both working and protect ports. The failover time meets the Bellcore-GR-253 standard of 50 ms. 1+1 APS is optional per port pair. For multi-port interfaces, each 1+1 APS port pair is independent of the others.
Service Generator Fabric 22 is the heart of IPSG 20. It is a fully meshed, 8-port shared memory switch that provides full-duplex communication between any pair of ports. The ports are non-blocking. All system-wide packet traffic as well as control messages pass through Service Generator Fabric 22. Service Generator Fabric 22 treats control messages with a higher priority than packet traffic. The Service Generator Fabric 22 employs a shared memory architecture with a total aggregated throughput of 51.2 Gbps. Ports can be attached to VREs, VSEs, ASEs, the Line Interface/Network Module 24 and the Midplane Interface 25.
The full-duplex communication link for each port pair runs at 3.2 Gbps in each direction, using a time-division streaming data interface protocol. In one embodiment, the time division allows the Service Generator Fabric 22 to serve each of eight input and output port with equal 32 byte size time slots, in round robin fashion, all at OC-48/STM-16+ rates. Other priority schemes can be implemented as needed.
In one embodiment, all the ports feeding data into and taking data out of the Service Generator Fabric 22 are store-and-forward to minimize the per packet transit time through the Service Generator Fabric 22.
When a packet is ready to be transferred from a Line Interface/Network Module 24 ingress to a destination VRE, it is streamed over to the Service Generator Fabric 22 shared memory in 32 byte chunks at OC-48/STM-16+ rates. Service Generator Fabric 22 examines the destination port's availability and then starts to stream the packet over to the destination port in 32 byte chunks at OC-48/STM-16+ rates.
At the same time, if a Service Generator Fabric port has a packet destined for a Line Interface/Network Module egress, it will also be streamed over to the Service Generator Fabric shared memory in 32 byte chunks at OC-48/STM-16+ rates. This time-shared cut-through protocol allows the shared memory to remain small (32 Kbytes).
Because the Service Generator Fabric is the single most traveled path by all packets, it has built in reliability. All port links are protected by Cyclical Redundancy Checking (CRC). CRC is an error detection mechanism that prevents bad packets from propagating beyond one pass through Service Generator Fabric 22.
As noted above, in one embodiment, the basic computing resources in a VSE and a VRE consist of 600 MHz IBM PowerPC 750CX CPUs. These CPUs offer advanced computing features such as two levels of internal caches and instruction execution optimization 3. Each CPU delivers 1200 MIPS; a fully populated IPSG 20 can offer as much as 10,800 MIPS, and a fully loaded switch 10 can deliver 130,000 MIPS.
A powerful multi-processing CPU enables high-level software, applications and underlying computing processes to execute at the highest possible speed. These CPUs can also work efficiently together in parallel to share computing data structures and workload.
In order to deliver a world-class services switching platform that moves and processes packets at high rates, in addition to executing software programs and processes, the multiple CPUs on the VSE and VRE are coupled with the Virtual Service Controller for accelerating virtual services packet processing and the Virtual Routing Processor for accelerating virtual routing functions. In one embodiment, the VSE and VRE can be thought of having a unified architecture (see FIG. 9). The VSE has one more CPU than the VRE, while the VRE has the Virtual Routing Processor and its associated memory 31.
Packet movement in and out of memory has been shown to be a bottleneck in server-based routers because the SDRAM-based memory subsystem is designed for the needs of data transfer, not packet transfer. Packet transfer does not use memory bandwidth as efficiently as data transfer. Sixty-four byte packets with random arrival and departure can cut memory efficiency by 40 percent or more. Moreover, in those routers, the packets originate and end on add-on I/O cards that are subject to I/O bus bottleneck. The typical I/O bus is a PCI-66, which at its best cannot support full OC-12/STM-4 rate.
In more conventional routers, e.g., Cisco routers, I/O bottleneck is eliminated but the CPU and memory subsystem performance is below that of server-based routers. These routers were not purpose-built to run services like VPNs, firewall or anti-virus. Furthermore, both types of routers cannot support more than a dozen routing instances in one box.
In one embodiment, these issues have been addressed within the multi-CPU memory subsystem by introducing advanced system memory and packet transfer control.
In one such embodiment, the packets in transit through the VSE or VRE are stored in the 1 GB external main memory 36, much like a server-based router. However, that is where the similarity ends. A server-based conventional router fetches network I/O packet transfer control information from software-controlled data structures in main memory across an I/O bus, typically a PCI bus. The same I/O bus is also used for packet transfer. In the IPSG 20 Virtual Service Controller 32, packet transfer control information is stored and managed at wire speed entirely in the local hardware. Software control of the data structures uses a separate interface and does not compete with actual packet transfer for main memory bandwidth. This way, main memory bandwidth is optimized for packet transfer.
The main memory bandwidth is still shared between data transfer (for CPU to run services) and packet transfer. The Virtual Service Controller includes a super high-performance (12.8 Gbps) memory controller. Innovative design technique using pipelined interface protocol and optimized memory access arbitration make this high performance possible. Both data and packet transfers can take advantage of this high bandwidth.
In one embodiment, the virtual routing function within the virtual routing processor 30 is micro-code based and supports a RISC-like instruction set. Packet classification and fast path packet forwarding are performed in hardware at wire speed, with the flexibility needed to stay current with the ever-evolving Internet standards. The CPUs are offloaded to dedicate more resources to running applications and software processes. The virtual routing function provides fast path packet forwarding for established flows. (In this embodiment, a flow is an ACL-level flow. An ACL is an ordered set of rules in a table that associates a group of packet header fields to the action that needs to be performed on such packets with matching header fields. For TCP/IP, for example, the header fields include internal control ID, IP source and destination addresses, TCP/UDP source and destination port numbers, IP TOS field and Layer 3 protocol field.)
The virtual routing function adapts design techniques from superscalar computing architecture, where there are a number of identical execution units in parallel, all executing the same program simultaneously but on different packets. Each unit is furthered pipelined into stages to allow overlapped packet processing. This is necessary to meet the gigabit wire-speed requirement for thousands of simultaneously active VRs.
A packet typically arrives from a Line Interface/Network Module 24 through the Service Generator Fabric 22 into one of the packet classifiers in the Virtual Routing Processor 30. In one embodiment, the packet's flow index is identified by extracting various Layer 2-4 fields of the packet header such as IP TOS, protocol, source address, destination address fields, TCP/UDP source and destination port fields. The packet classifier executes micro-code instructions to extract bit and byte fields and even perform Boolean functions for this purpose. In one embodiment, a hash function is applied to the contents of the fields to obtain an address into a flow cache storing a predetermined number of forward indexes.
Upon a match in the flow cache, a forward index is obtained to address another table that contains the blueprint for packet field manipulation, that is, packet processing. For example, the blueprint can specify the action for firewall filtering, which is to drop the packet. Another example is the act of routing, which includes substituting the Layer 2 destination address with next hop value, decrementing Time-To-Live (TTL) and performing IP header checksum adjustment. A third example is NAT, which includes substituting original IP source and/or destination address, TCP/UDP source and/or destination port values. A fourth example is DiffServ TOS field marking, flow metering and rate control. A fifth example is to update packet statistics to support event logging. Yet another example is GRE tunneling, which includes the encapsulation of the original packet header by another packet header.
The blueprint can also specify that the packet be processed, such as the case of URL filtering or anti-virus scanning, which requires parsing of packet payload by a general CPU. Before a flow is set up by software, all packets arriving at the packet classifiers will be sent to software for first time forwarding. Software running on the CPUs 34 sets up routing tables and forwarding information bases as well as the packet processing action table entries associated with each established flow. Thereafter, all packets will be sent to the outbound network interface without ever being touched by software, as long as the flows they belong to are cached in the flow cache. In one embodiment, VRE performance is at 3 Million packets per second (Mpps).
The routing processes described above is described in greater detail in “SYSTEM AND METHOD FOR ROUTING TRAFFIC THROUGH A VIRTUAL ROUTER-BASED NETWORK SWITCH,” the descriptions of which are incorporated herein by reference.
DiffServ QoS support in Virtual Routing Processor 30 includes TOS field update and rate control. Rate control includes packet rate metering, marking and dropping functions. Rate control comes in several flavors, which are not mutually exclusive: Ingress rate control based on the VI, rate control based on the flow to which the packet belongs, and egress rate control after the packet is routed and forwarded.
In one embodiment, rate metering and marking is implemented completely in hardware for each flow. The hardware supports the concept of the color-blind and color-aware packet. In color-blind mode, the incoming packet color is ignored, and any color can be added to the packet. In color-aware mode, the incoming packet color is taken into consideration. In this case, the incoming packet can be green, yellow or red. Green packets have the lowest probability of being dropped and will be dropped last if necessary. If the incoming packet is green, the packet can stay green or it can be downgraded to yellow or red; a packet can never be upgraded.
The two-rate three-color metering based on RFC 2698 marks its packets green, yellow or red. A packet is marked red if it exceeds the Peak Information Rate (PIR). Otherwise it is marked either yellow or green depending on whether it exceeds or doesn't exceed the Committed Information Rate (CIR). It is useful, for example, for ingress policing of a service where a peak rate needs to be enforced separately from a committed rate. The packet's color is encoded in the internal control header of the packet and will be interpreted by Flow Manager 26 for congestion control purpose. The metering context is stored in main memory. The metering context contains status and state information, such as number of bytes metered green, yellow and red, the PIR in bytes/time slot, CIR in bytes/time slot, etc. This metering context is updated every time a packet is processed.
The QoS processes are described in “SYSTEM AND METHOD FOR HIERARCHICAL METERING IN A VIRTUAL ROUTER BASED NETWORK SWITCH,” “METHODS AND SYSTEMS FOR A DISTRIBUTED PROVIDER EDGE,” and “SYSTEM AND METHOD FOR ROUTING TRAFFIC THROUGH A VIRTUAL ROUTER-BASED NETWORK SWITCH,” the descriptions of which are incorporated herein by reference.
The Advanced Security Engine (AES) will be described next.
Creating, terminating and transporting IPSec tunnels is an integral part of IPSec-based VPNs, and encryption, decryption and authentication processes are an integral part of any secure transaction. These are all notoriously computation-intensive functions. The ASE consists of four Hi/fn 7851 encryption accelerators, a Hi/fi 6500 key accelerator and a Security Manager 38 (see FIG. 9). Security Manager 38 performs the following functions: load balancing and managing security sessions across four Hi/fn 7851 encryption accelerators for wire speed throughput at 1+ Gbps, facilitating programming of registers for four Hi/fn 7851 encryption accelerators and one Hi/fn 6500 key accelerator and providing system control header and security command message header translation.
The Hi/fn 7851 security processor features an embedded RISC CPU that performs all the packet header and trailer processing at 155 Mbps for back-to-back minimum size packets and at 622 Mbps for back-to-back maximum size 1500 byte packets. For each Hi/fn 7851, a 64 MB SDRAM is used to store over 16,000 active security associations (with a theoretical maximum of 230,000). The Hi/fn 7851 processor provides the following functions for IPSec: 3DES/RC4 encryption/decryption for packets to/from access (subscriber) side, IPSec header (ESP/AH) encapsulation and parsing, SHA or MD-5 authentication service for packets to/from access (subscriber) side, support for Public Key Infrastructure (PKI) with RSA/Diffie-Hellman/DSA key algorithms and, optionally, LZS/MPPC-based compression/decompression for packets to/from access (subscriber) side.
Packets that have been classified by the VRE arrive at the ASE for IPSec tunnel creation or termination. Security Manager 38 decodes the security session ID for the packet. Then it strips off the system control header and stores it in a SRAM. Security Manager 38 creates and prepends a Hi/fn command message header to the original packet, directing it to the corresponding Hi/fn 7851. The Hi/fn 7851 performs authentication and encryption or decryption services. In the case of encryption, encryption is applied to the IP packet and an IPSec ESP/AH header is prepended to it. The IPSec header is pieced together from information contained in the original packet control header as well as the Hi/fn results header. This ensures the QoS information in the original IP header is preserved.
At a given time, all four Hi/fn 7851s can be in various states of processing of up to a total of four packets. The streaming bus is non-blocking; that is, a smaller packet destined to one Hi/fn 7851 will not be blocked behind a large packet to another Hi/fn 7851. This ensures that the ASE optimizes the aggregate throughput of all the Hi/fn 7851s combined.
The Midplane Interface 25 is where packets leave the IPSG to go to another IPSG 20 or where packets arrive from another IPSG 20. In one embodiment, Midplane Interface 25 is a 22 Gbps dual counter-rotating ring structure that is redundant, high performance and deterministic in the transmission of packets. The Midplane Interface includes a Flow Manager 26 with the same queuing and congestion control features discussed in connection with Line Interface/Network Module 24 above.
The IPNOS discussed above has an architectural structure that dovetails perfectly with the IPSG architecture. IPSG 20 has been designed to deliver tailored hardware processing resources to address specific IP services, and IPNOS provides the framework to take advantage of those hardware capabilities. IPNOS is a distributed, object-oriented, multi-processor operating system designed to be scalable by dynamically allocating service elements to the best available resources. All IP services, networks and even physical resources (e.g., processors and access circuits) are managed as objects or groups of objects by IPNOS.
As a service processing OS, IPNOS builds a foundation for customized subscriber-level IP services through the VR concept. IPNOS creates a VR as an object group and has the capacity to create tens of thousands of object groups. As the name implies, an object group is a group of independent objects (of the same or different types). A single object group can contain tens of objects. There are a number of different types of objects in IPNOS: device driver object, link layer object, TCP/IP object, application object, etc.
The object model that IPNOS employs conforms roughly to the standard OSI model for networks (see FIG. 10). As in a true object model, objects themselves are comprised of data definitions and various methods. With careful data design, objects enable efficient distributed processing by allowing a larger entity to be split into smaller pieces. Objects execute or .invoke. methods to react to events such as the arrival of data packets. Objects can invoke either their own methods or remote methods residing in other objects. If a recipient object does not yet exist, the requesting object informs the Object Manager, which instantiates the new required object. In this way, objects interact with each other to accomplish larger processing tasks.
One of the pieces of data for each object is the type of processing resource it needs to execute. Thus, when the Object Manager is asked to instantiate a new object, it knows what kind of resource it needs and can draw from the available pool of those tailored resources instead of leveraging only generally available CPUs. For example, when an IPSec tunnel needs to be created, the object group (a VR) requests a new IPSec object to be created on an available ASE. This ability to dynamically distribute processing to tailored resources allows IPNOS to optimize all the processing power designed into the system. In addition, it enables some of the parallelism for packet processing that gives IPSG 20 its ability to operate at wire speed.
This process is described in greater detail in “SYSTEM AND METHOD FOR CONTROLLING ROUTING IN A VIRTUAL ROUTER SYSTEM,” described above, the description of which is incorporated herein by reference.
A step-by-step description of a representative packet flow through IPSG 20 will be described next. The illustration in FIG. 11 shows the complete journey of a minimum size frame through an IPSG 20. Customer VLAN-based traffic gets tunneled through a Sub VR IPSec tunnel in VRE-1 and then routed to an SP IP core though an SP VR in VRE-2.
1. An 802.1q VLAN Ethernet packet arrives at a Gigabit Ethernet input port on the Line Interface/Network Module 24. The Flow Manager 26 programs the steering table look-up and decides which VLAN goes to which VRE. Flow Manager 26 tags the packet with an internal control header and transfers it from the Line Interface/Network Module 24 across the Service Generator Fabric 22 to the selected VRE.
2. Upon arrival at the VRE, the packet enters the Virtual Service Controller 32 for deep packet classification. Based on the instructions in the Virtual Service Controller's micro-code, various fields of the packet header, i.e., IP source and destination addresses, UDP/TCP source and destination port numbers, IP protocol field, TOS field, IPSec header and SPI field are extracted. An ACL flow associated with the packet is identified. A flow cache is consulted to find out whether the packet should be forwarded in software or hardware. (In this scenario, the packet is to be processed in hardware and an index to the packet processing action cache is obtained.) The ingress VI metering and statistics are registered as part of the ingress flow processing.
3. The packet is deposited via high-speed Direct Memory Access (DMA) into the VRE's main memory and then becomes accessible to the Virtual Routing Processor 30.
4. Virtual Routing Processor 30 retrieves the packet, identifies the packet processing actions that can be achieved in hardware and then performs those actions, such as time-to-live decrement, IP header checksum adjustment and IP forwarding patch matching. The egress statistics counters are updated.
5. The packet is forwarded to the ASE.
6. In the ASE, the packet gets encrypted and time-to-live is decremented. The ASE performs encryption and prepends an IPSec tunnel header.
7. The IPSec tunneled packet is handed back to the Sub VR in the VRE, which decides where to forward the packet (in this case, to the SP VR in VRE-2).
8. As the packet leaves the VRE-1 for the SP VR in VRE-2, the following are processed: a. Egress VI statistics, b. VI metering and marking, c. VI maximum transmit unit enforcement, and d. Packet fragmentation (if necessary).
9. The packet arrives at the SP VR in VRE-2. It goes to the hardware FIB lookup, gets forwarded through the SP VR interface toward the SP core. At the egress, VI statistics and metering are performed.
10. The egress Flow Manager 26 applies priority queuing based on DiffServ marking and transmits the packet out of IPSG 20.
FIG. 12 is a flow diagram illustrating a packet forwarding process in accordance with one embodiment of the present invention. According to the present example, a packet is received at a line interface/network module of a switch at block 1210.
At block 1220, the packet is forwarded to a virtual routing engine (VRE) of the switch.
At block 1230, flow-based packet classification is performed on the packet and forwarding state information associated with the previously stored flow learning results is evaluated. According to one embodiment, two basic forms of packet classification are supported. One is flow-based using various fields of the LQ header along with fields in the L3/L4 headers to identify a particular VR micro-flow. The other form uses the upper bits of the IP address or MPLS label to index a table of flow indices. In one embodiment, the host software controls which classification form is used. In both forms, the classification may result in a 20-bit forwarding index that the hardware may use to select the correct packet transformations from a flow cache.
At decision block 1240, based on flow cache entry retrieved based on the packet classification result, it is determined whether the packet requires processing by a virtual services engine, such as an advanced security engine (ASE) of the switch. If so, processing continues with block 1250; otherwise processing branches to block 1260.
At block 1250, the packet is steered to the virtual services engine for appropriate processing and then the packet is forwarded to the destination.
At block 1260, the packet is forwarded to the destination without first being processed by the virtual services engine.
CONCLUSION
Systems and method for providing IP services have been described. The systems and methods described provide advantages over previous systems.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present invention.
The terminology used in this application is meant to include all of these environments. It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. Therefore, it is manifestly intended that this invention be limited only by the following claims and equivalents thereof.

## Claims

1. A method comprising:
establishing a flow cache having a plurality of entries each identifying one of a plurality of virtual router (VR) flows through a VR-based network device and corresponding forwarding state information;
receiving a packet at an input port of a line interface module of the VR-based network device;
the line interface module forwarding the packet to a virtual routing engine (VRE);
the VRE determining one or more appropriate packet transformations for application to the packet by performing flow-based packet classification on the packet;
using a result of the flow-based packet classification to retrieve an entry of a plurality of entries of the flow cache;
on a flow cache hit, determining, based on the corresponding forwarding state information of the retrieved flow cache entry, whether to process the packet with a virtual service engine (VSE) of the VR-based network device;
on a packet flow cache miss, identifying the existence of a new VR flow and upon successful allocation of a new entry of the packet flow cache for the new VR flow, forwarding the packet to software on the processor for flow learning.

2. The method of claim 1, wherein the VSE comprises an Advanced Security Engine (ASE).

3. An article of manufacture comprising a computer-readable medium encoded with one or more computer programs, which when executed by one or more processors of a virtual router (VR)-based network device cause the one or more processors to perform a method comprising:
establishing a flow cache having a plurality of entries each identifying one of a plurality of VR flows through the VR-based network device and corresponding forwarding state information;
receiving a packet at an input port of a line interface module of the VR-based network device;
the line interface module forwarding the packet to a virtual routing engine (VRE);
the VRE determining one or more appropriate packet transformations for application to the packet by performing flow-based packet classification on the packet;
using a result of the flow-based packet classification to retrieve an entry of a plurality of entries of the flow cache;
on a flow cache hit, determining, based on the corresponding forwarding state information of the retrieved flow cache entry, whether to process the packet with a virtual service engine (VSE) of the VR-based network device;
on a packet flow cache miss, identifying the existence of a new VR flow and upon successful allocation of a new entry of the packet flow cache for the new VR flow, forwarding the packet to software on the processor for flow learning.

4. The article of manufacture of claim 3, wherein the VSE comprises an Advanced Security Engine (ASE).

5. A virtual router (VR)-based network device comprising:
a means for establishing a flow cache having a plurality of entries each identifying one of a plurality of virtual router (VR) flows through a VR-based network device and corresponding forwarding state information;
a means for receiving a packet at an input port of a line interface module of the VR-based network device and for forwarding the packet to a virtual routing engine (VRE);
a means associated with the VRE for determining one or more appropriate packet transformations for application to the packet by performing flow-based packet classification on the packet;
a means for using a result of the flow-based packet classification to retrieve an entry of a plurality of entries of the flow cache;
a means for, on a flow cache hit, determining, based on the corresponding forwarding state information of the retrieved flow cache entry, whether to process the packet with a virtual service engine (VSE) of the VR-based network device;
a means for, on a packet flow cache miss, identifying the existence of a new VR flow and upon successful allocation of a new entry of the packet flow cache for the new VR flow, forwarding the packet to software on the processor for flow learning.

6. The VR-based network device of claim 5, wherein the VSE comprises an Advanced Security Engine (ASE).