Packet processing

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In digital communications networks, packet processing refers to the wide variety of algorithms that are applied to a packet of data or information as it moves through the various network elements of a communications network. With the increased performance of network interfaces, there is a corresponding need for faster packet processing. [1]

Contents

There are two broad classes of packet processing algorithms that align with the standardized network subdivision of control plane and data plane. The algorithms are applied to either:

  • Control information contained in a packet which is used to transfer the packet safely and efficiently from origin to destination
or
  • The data content (frequently called the payload) of the packet which is used to provide some content-specific transformation or take a content-driven action.

Within any network enabled device (e.g. router, switch, network element or terminal such as a computer or smartphone) it is the packet processing subsystem that manages the traversal of the multi-layered network or protocol stack from the lower, physical and network layers all the way through to the application layer.

History

The history of packet processing is the history of the Internet and packet switching. Packet processing milestones include:

Historical references and timeline can be found in the External Resources section below.

Communications models

For networks to succeed it is necessary to have a unifying standard for which defines the architecture of networking systems. The fundamental requirement for such a standard is to provide a framework that enables the hardware and software manufacturers around the world to develop networking technologies that will work together and to harness their cumulative investment capabilities to move the state of networking forward.

In the 1970s, two organizations, the International Organization for Standardization [2] (ISO) and the International Telegraph and Telephone Consultative Committee [3] (CCITT, now called the International Telecommunication Union (ITU-T) each initiated projects with the goal of developing international networking standards. In 1983, these efforts were merged and in 1984 the standard, called The Basic Reference Model for Open Systems Interconnection, [4] was published by ISO and as standard X.200 [5] by the ITU-T.

The OSI Model is a 7 layer model [6] describing how a network operating system works. A layered model has many benefits [7] including the ability to change one layer without impacting the others and as a model for understanding how a network OS works. As long as the interconnection between layers is maintained, vendors can enhance the implementation of an individual layer without impact on other layers.

In parallel with the development of the OSI model, a research network was being implemented by the United States Defense Advanced Research Projects Agency [8] (DARPA). The internetworking protocol developed to support the network, called ARPAnet, [9] was called TCP or Transmission Control Program. As research and development progressed and the size of the network grew, it was determined that the internetworking design that was being used was becoming unwieldy and it did not exactly follow the layered approach of the OSI Model. This led to the splitting of the original TCP and the creation of the TCP/IP architecture [10] - TCP now standing for Transmission Control Protocol and IP standing for Internet Protocol.

Advent of packet processing

Packet networks [11] came about as a result of the need in the early 1960s to make communications networks more reliable. It can be viewed as the implementation of the layered model using a packet structure.

Early commercial networks were composed of dedicated, analog circuits used for voice communications. The concept of packet switching was introduced to create a communications network that would continue to function in spite of equipment failures throughout the network. In this paradigm shift, networks are viewed as collections of systems that transmit data in small packets that work their way from origin to destination by any number of routes. Initial packet processing functions supported the routing of packets through the network, transmission error detection and correction and other network management functions.

Packet switching with its supporting packet processing functions has several practical benefits over traditional circuit-switched networks: [12]

Packet structure

A network packet is the fundamental building block for packet-switched networks. [15] When an item such as a file, e-mail message, voice or video stream is transmitted through the network, it is broken into chunks called packets that can be more efficiently moved through the network than one large block of data. Numerous standards [16] cover the structure of packets, but typically packets are composed of three elements:

In a packet-switched network, the sending host computer packetizes the original item and each packet is routed through the network to its destination. Some networks used fixed length packets, typically 1024 bits, while others use variable length packets and include the packet length in the header.

Individual packets may take different routes to the destination and arrive at the destination out of order. The destination computer verifies the correctness of the data in each packet (using information in the trailer), reassembles the original item using the packet number information in the header, and presents the item to the receiving application or user.

This basic example includes the three most fundamental packet processing functions, packetization, routing, and assembly. Packet processing functions range from the simple to highly complex. As an example, the routing function is actually a multi-step process [17] involving various optimization algorithms and table lookups. A basic routing function on the Internet looks something like:

1. Check to see if the destination is an address ‘owned’ by this computer. If so, process the packet. If not:
a. Check to see if IP Forwarding is set to ‘Yes’. If no, the packet is destroyed. If yes, then
i. Check to see if a network attached to this computer owns the destination address. If yes, route the packet to the appropriate network. If no, then
1. Check to see if there is any route to the destination network. If yes, route the packet to the next hop gateway. If no, destroy the packet.

More advanced routing functions include network load balancing [18] and fastest route algorithms. [19] These examples illustrate the range of packet processing algorithms possible and how they can introduce significant delays [20] into the transmission of an item. Network equipment designers frequently use a combination of hardware and software accelerators to minimize the latency in the network.

Network equipment architecture

IP-based equipment can be partitioned into three basic elements: data plane, control plane and management plane. [21]

Data plane

The data plane is a subsystem of a network node that receives and sends packets from an interface, processes them as required by the applicable protocol, and delivers, drops, or forwards them as appropriate.

Control plane

The control plane maintains information that can be used to change data used by the data plane. Maintaining this information requires handling complex signaling protocols. Implementing these protocols in the data plane would lead to poor forwarding performance. A common way to manage these protocols is to let the data plane detect incoming signaling packets and locally forward them to the control plane. The control plane signaling protocols can update the data plane information and inject outgoing signaling packets into the data plane. This architecture works because signaling traffic is a very small part of the global traffic.

Management plane

The management plane provides an administrative interface into the overall system. It contains processes that support operational administration, management or configuration/provisioning actions such as:

More sophisticated solutions based on XML (eXtensible Markup Language) can also be included.

Examples

The list of packet processing applications [22] is usually divided into two categories. The following are a few examples selected to illustrate the variety in use today.

Control applications

Data applications

Packet processing architectures

Packet switching [24] also introduces some architectural compromises. Performing packet processing functions in the transmission of information introduces delays that may be detrimental to the application being performed. For example, in voice and video applications, the necessary conversion from analog-to-digital and back again at the destination along with delays introduced by the network can cause noticeable gaps that are disruptive to the users. Latency is a measure of the time delay experienced by a complex system.

Multiple architectural approaches to packet processing have been developed [25] to address the performance and functionality requirements of a specific network and to address the latency issue.

Single threaded architecture (standard operating system)

A standard networking stack uses services provided by the Operating System (OS) running on a single processor (single threaded). While single threaded architectures are the simplest to implement, they are subject to overheads associated with the performance of OS functions such as preemptions, thread management, timers and locking. These OS processing overheads are imposed on each packet passing through the system, resulting in a throughput penalty.

Multi-threaded architecture (multi-processing operating system)

Performance improvements can be made to an OS networking stack by adapting the protocol stack processing software to support multiple processors (multi-threaded), either through the use of Symmetrical Multiprocessing (SMP) platforms or multicore processor architecture. Performance increases are realized for a small number of processors, [26] but fails to scale linearly over larger numbers of processors (or cores) and a processor with, for example, eight cores may not process packets significantly faster than one with two cores.

Fast path architecture (operating system by-pass)

In a fast path implementation, the data plane is split into two layers. The lower layer, typically called the fast path, processes the majority of incoming packets outside the OS environment and without incurring any of the OS overheads that degrade overall performance. Only those packets that require complex processing are forwarded to the OS networking stack (the upper layer of the data plane), which performs the necessary management, signaling and control functions. When complex algorithms such as routing or security are required, the OS networking stack forwards the packet to dedicated software components in the control plane.

A multicore processor can provide additional performance improvement to a fast path implementation. [27] In order to maximize the overall system throughput, multiple cores can be dedicated to running the fast path, while only one core is required to run the Operating System, the OS networking stack and the application’s control plane.

The only restriction when configuring the platform is that, since the cores running the fast path are running outside the OS, they must be dedicated exclusively to the fast path and not shared with other software. The system can also be reconfigured dynamically as traffic patterns change. Splitting the data plane into two layers also adds complexity as the two layers must have the same information to ensure system consistency.

Packet processing technologies

In order to create specialized packet processing platforms, a variety of technologies have been developed and deployed. These technologies, which span the breadth of hardware and software, have all been designed with the aim of maximizing speed and throughput while minimizing latency.

Network processors

A network processor unit (NPU) is similar in many respects to general purpose processors (GPP) that power most computers but with its internal architecture and functions tailored to network-centric operations. NPUs commonly have network-specific functions such as address lookup, pattern matching and queue management built into their microcode. Higher level packet processing operations such as security or intrusion detection are often built into NPU architectures. [28] Network processor examples would include:

Multicore processors

A multicore processor is a single semiconductor package that has 2 or more cores, each representing an individual processing unit, capable of executing code in parallel. General purpose CPUs such as the Intel Xeon [29] now support up to 8 cores. Some multicore processors integrate dedicated packet processing capabilities to provide a complete SoC (System on Chip). They generally integrate Ethernet interfaces, crypto-engines, pattern matching engines, hardware queues for QoS and sometimes more sophisticated functions using micro-cores. All these hardware features are able to offload the software packet processing. Recent examples of these specialized multicore packages, such as the Cavium OCTEON II, can support from 2 up to 32 cores.

Hardware accelerators

For clearly definable and repetitive actions, creating a dedicated accelerator built directly into a semiconductor hardware solution will speed up operations when compared to software running on a general purpose processor. [30] Initial implementations used FPGAs (field-programmable gate array) or ASICs (Application-specific Integrated Circuit), but now specific functions such as encryption and compression are built into both GPPs and NPUs as internal hardware accelerators. Current multicore processor examples with network-specific hardware accelerators include the Cavium CN63xx with acceleration for security, TCP/IP, QOS and HFA pattern matching [31] and the Netlogic Microsystems XFS processor family with networking and security acceleration engines. [32]

Deep packet inspection

Being able to make decisions based on the content of individual packets enables a wide variety of new applications such as policy and charging rules function (PCRF) and Quality of Service. Packet processing systems separate out specific traffic types through the use of Deep Packet Inspection (DPI) [33] technologies. DPI technologies utilize pattern matching algorithms to look inside the data payload to identify the contents of each and every packet flowing through a network device. Successful pattern matches are reported to the controlling application for any appropriate further action to be taken.

Packet processing software

Operating system software will contain certain standard network stacks that will operate in both single and multicore environments. [34] To be able to implement operating system by-pass (fast path) architectures requires the use of specialized packet processing software such as 6WIND's 6WINDGate. This type of software provides a suite of networking protocols that can be distributed across multiple blades, processors or cores and scale appropriately.

Related Research Articles

Internetworking is the practice of interconnecting multiple computer networks, such that any pair of hosts in the connected networks can exchange messages irrespective of their hardware-level networking technology. The resulting system of interconnected networks are called an internetwork, or simply an internet.

The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information indicating success or failure when communicating with another IP address. For example, an error is indicated when a requested service is not available or that a host or router could not be reached. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications.

The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and the Internet Protocol (IP). Early versions of this networking model were known as the Department of Defense (DoD) model because the research and development were funded by the United States Department of Defense through DARPA.

<span class="mw-page-title-main">OSI model</span> Model of communication of seven abstraction layers

The Open Systems Interconnection model is a reference model from the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection." In the OSI reference model, the communications between systems are split into seven different abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

<span class="mw-page-title-main">Protocol stack</span> Comprehensive computer networking implementation

The protocol stack or network stack is an implementation of a computer networking protocol suite or protocol family. Some of these terms are used interchangeably but strictly speaking, the suite is the definition of the communication protocols, and the stack is the software implementation of them.

<span class="mw-page-title-main">Router (computing)</span> Device that forwards data packets between computer networks

A router is a computer and a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions between networks and on the global Internet. Data sent through a network, such as a web page or email, is in the form of data packets. A packet is typically forwarded from one router to another router through the networks that constitute an internetwork until it reaches its destination node.

<span class="mw-page-title-main">Wake-on-LAN</span> Mechanism to wake up computers via a network

Wake-on-LAN is an Ethernet or Token Ring computer networking standard that allows a computer to be turned on or awakened from sleep mode by a network message.

<span class="mw-page-title-main">Protocol data unit</span> Unit of information transmitted over a computer network

In telecommunications, a protocol data unit (PDU) is a single unit of information transmitted among peer entities of a computer network. It is composed of protocol-specific control information and user data. In the layered architectures of communication protocol stacks, each layer implements protocols tailored to the specific type or mode of data exchange.

<span class="mw-page-title-main">Transport layer</span> Layer in the OSI and TCP/IP models providing host-to-host communication services for applications

In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end communication services for applications. It provides services such as connection-oriented communication, reliability, flow control, and multiplexing.

A virtual private network (VPN) is a mechanism for creating a secure connection between a computing device and a computer network, or between two networks, using an insecure communication medium such as the public Internet.

The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer.

A multilayer switch (MLS) is a computer networking device that switches on OSI layer 2 like an ordinary network switch and provides extra functions on higher OSI layers. The MLS was invented by engineers at Digital Equipment Corporation.

An overlay network is a computer network that is layered on top of another network. The concept of overlay networking is distinct from the traditional model of OSI layered networks, and almost always assumes that the underlay network is an IP network of some kind.

Networking hardware, also known as network equipment or computer networking devices, are electronic devices that are required for communication and interaction between devices on a computer network. Specifically, they mediate data transmission in a computer network. Units which are the last receiver or generate data are called hosts, end systems or data terminal equipment.

A network socket is a software structure within a network node of a computer network that serves as an endpoint for sending and receiving data across the network. The structure and properties of a socket are defined by an application programming interface (API) for the networking architecture. Sockets are created only during the lifetime of a process of an application running in the node.

The internet layer is a group of internetworking methods, protocols, and specifications in the Internet protocol suite that are used to transport network packets from the originating host across network boundaries; if necessary, to the destination host specified by an IP address. The internet layer derives its name from its function facilitating internetworking, which is the concept of connecting multiple networks with each other through gateways.

<span class="mw-page-title-main">Forwarding plane</span>

In routing, the forwarding plane, sometimes called the data plane or user plane, defines the part of the router architecture that decides what to do with packets arriving on an inbound interface. Most commonly, it refers to a table in which the router looks up the destination address of the incoming packet and retrieves the information necessary to determine the path from the receiving element, through the internal forwarding fabric of the router, and to the proper outgoing interface(s).

A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics, and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both.

<span class="mw-page-title-main">SoftEther VPN</span> Open-source VPN client and server software

SoftEther VPN is free open-source, cross-platform, multi-protocol VPN client and VPN server software, developed as part of Daiyuu Nobori's master's thesis research at the University of Tsukuba. VPN protocols such as SSL VPN, L2TP/IPsec, OpenVPN, and Microsoft Secure Socket Tunneling Protocol are provided in a single VPN server. It was released using the GPLv2 license on January 4, 2014. The license was switched to Apache License 2.0 on January 21, 2019.

The Protocol Wars were a long-running debate in computer science that occurred from the 1970s to the 1990s, when engineers, organizations and nations became polarized over the issue of which communication protocol would result in the best and most robust networks. This culminated in the Internet–OSI Standards War in the 1980s and early 1990s, which was ultimately "won" by the Internet protocol suite (TCP/IP) by the mid-1990s when it became the dominant protocol through rapid adoption of the Internet.

References

  1. ↑ D. Cerović, V. Del Piccolo, A. Amamou, K. Haddadou and G. Pujolle, Fast Packet Processing: A Survey, in IEEE Communications Surveys & Tutorials, vol. 20, no. 4, pp. 3645-3676, Fourthquarter 2018. doi: 10.1109/COMST.2018.2851072
  2. ↑ International Organization for Standardization
  3. ↑ International Telecommunication Union)
  4. ↑ ISO/IEC 10731:1994. Information technology -- Open Systems Interconnection -- Basic Reference Model -- Conventions for the definition of OSI services
  5. ↑ ITU-T X.200-199407, X.200 : Information technology - Open Systems Interconnection - Basic Reference Model: The basic model
  6. ↑ Tech-FAQ. The OSI Model – What It Is; Why It Matters; Why It Doesn’t Matter
  7. ↑ Computer Networking Notes. Advantages of OSI 7 Layer Model
  8. ↑ "DARPA - Defense Advanced Research Projects Agency". Archived from the original on 2020-01-15. Retrieved 2012-01-05.
  9. ↑ Living Internet. ARPANET -- The First Internet
  10. ↑ W3 Schools, TCP/IP Tutorial
  11. ↑ Sheldon, Tom. Packets and Packet Processing Networks. Linktionary, 2001.
  12. ↑ Copeland, Lee. QuickStudy: Packet-Switched vs. Circuit-Switched Networks. Computerworld, March 2000.
  13. ↑ Negroponte, N. Being Digital. Vintage, Jan. 1996.
  14. ↑ Reding, Viviane. Digital convergence: a whole new way of life. Digital Lifestyle Exhibition, May 2006.
  15. ↑ Peterson, L. and Davie, B. Computer Networks (5th Edition): A Systems Approach. Morgon Kaufmann, March 2011.
  16. ↑ RFC Sourcebook. IP, Internet Protocol.
  17. ↑ Streenstrup, M. Routing in Communications Networks. Prentice Hall, April 1995.
  18. ↑ Anderson, P. and James, L. Performance soars, features vary - Review: Load Balancers. NetworkWorldFusion, June 1999.
  19. ↑ Murthy, S. Routing in Packet-Switched Networks Using Path-Finding Algorithms. UC Santa Cruz, 1996.
  20. ↑ U. of Maryland. Introduction, Rate and Latency. 2009
  21. ↑ Nokia Communications Framework Guide. What are Planes?. February 2010.
  22. ↑ Vin, H. Packet Processing Applications: An Overview. Univ. of Texas, Fall 2003.
  23. ↑ Reddy, M. Video Transcoding & Transrating - Video in 31 Flavors!. Vela, Sep. 2011.
  24. ↑ Elhanany, I. and Hamdi, M. High Performance Packet Switching Architectures. Springer, November 2011.
  25. ↑ Selissen, M. Packet Processing Needs Balanced Between Architecture, Network. EE Times, Aug 2002.
  26. ↑ Foong, A., Fung, J. and Newell, D. Improved Linux SMP Scaling: User-directed Processor Affinity. Intel Software Network, October 2008.
  27. ↑ CDC Innovation. 6WIND Provides 10x Acceleration of Packet Processing Functions on New multicore Intel® Platforms. March, 2010.
  28. ↑ NetLogic Microsystems. Advanced Algorithmic Knowledge-based Processors.
  29. ↑ Intel. Packet Processing with Intel® multicore Processors. 2008.
  30. ↑ Cheerla, R. Architecture Comparison For High Performance WAN Optimization Systems. Infineta, Cardinal Directions, March 2011.
  31. ↑ Cavium. OCTEON II CN63XX multicore MIPS64 Internet Application Processors
  32. ↑ NetLogic Microsystems. multicore Processor Solutions
  33. ↑ dpacket.org Introduction to Deep Packet Inspection/Processing.
  34. ↑ Multicore Packet Processing Forum
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