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{{Short description|Type of integrated circuit}}
[[File:Intel FWIXP422BB on mainboard of UMTS Router Surf@home II, o2-8338.jpg|300px|thumb|Intel FWIXP422BB]]
A '''network processor''' is an [[integrated circuit]] which has a feature set specifically targeted at the [[Computer networking|networking]] application domain.

Network processors are typically [[software]] programmable devices and would have generic characteristics similar to general purpose [[central processing unit]]s that are commonly used in many different types of equipment and products.

==History of development==
In modern [[telecommunications network]]s, information (voice, video, data) is transferred as [[Packet (information technology)|packet]] data (termed [[packet switching]]) which is in contrast to older telecommunications networks that carried information as [[analog signal]]s such as in the [[public switched telephone network]] (PSTN) or analog [[TV]]/[[Radio]] networks. The processing of these packets has resulted in the creation of [[integrated circuit]]s (IC) that are optimised to deal with this form of packet data. Network processors have specific features or architectures that are provided to enhance and optimise packet processing within these networks.

Network processors have evolved into ICs with specific functions. This evolution has resulted in more complex and more flexible ICs being created. The newer circuits are programmable and thus allow a single [[computer hardware|hardware]] IC design to undertake a number of different functions, where the appropriate [[software]] is installed.

Network processors are used in the manufacture of many different types of [[Networking hardware|network equipment]] such as:

* [[Router (computing)|Router]]s, [[software router]]s and [[Network switch|switches]] ([[Inter-network processors]])
* [[Firewall (networking)|Firewall]]s
* [[Session border controller]]s
* [[Intrusion detection system|Intrusion detection devices]]
* [[Intrusion prevention system|Intrusion prevention devices]]
* [[Network monitoring]] systems
* [[Network security]] ([[secure cryptoprocessor]]s)

=== Reconfigurable Match-Tables ===
Reconfigurable Match-Tables<ref>{{Cite journal |last1=Bosshart |first1=Pat |last2=Gibb |first2=Glen |last3=Kim |first3=Hun-Seok |last4=Varghese |first4=George |last5=McKeown |first5=Nick |last6=Izzard |first6=Martin |last7=Mujica |first7=Fernando |last8=Horowitz |first8=Mark |date=2013-08-01 |title=Forwarding Metamorphosis: Fast Programmable Match-Action Processing in Hardware for SDN |url=https://www.microsoft.com/en-us/research/publication/forwarding-metamorphosis-fast-programmable-match-action-processing-in-hardware-for-sdn/ |language=en-US}}</ref><ref name=":0">{{Cite book |last1=Gibb |first1=Glen |last2=Varghese |first2=George |last3=Horowitz |first3=Mark |last4=McKeown |first4=Nick |title=Architectures for Networking and Communications Systems |chapter=Design principles for packet parsers |date=October 2013 |chapter-url=https://ieeexplore.ieee.org/document/6665172 |pages=13–24 |doi=10.1109/ANCS.2013.6665172|isbn=978-1-4799-1641-2 |s2cid=12282067 }}</ref> were introduced in 2013 to allow switches to operate at high speeds while maintaining flexibility when it comes to the network protocols running on them, or the processing to does to them. [[P4 (programming language)|P4]]<ref>{{Cite web |title=P4: Programming Protocol-Independent Packet Processors {{!}} acm sigcomm |url=https://www.sigcomm.org/node/3503 |access-date=2022-03-26 |website=www.sigcomm.org |language=en}}</ref> is used to program the chips. The company [[Barefoot Networks]] was based around these processors and was later purchased by [[Intel]] in 2019.
[[File:RMT Fig.svg|thumb|RMP Pipeline Description]]
An RMT pipeline relies on three main stages; the programmable parser,<ref name=":0" /> the Match-Action tables and the programmable deparser. The parser reads the packet in chunks and processes these chunks to find out which protocols are used in the packet ([[Ethernet frame|Ethernet]], [[IEEE 802.1Q|VLAN]], [[IPv4]]...) and extracts certain fields from the packet into the Packet Header Vector (PHV). Certain fields in the PHV may be reserved for special uses such as present headers or total packet length. The protocols are typically programmable, and so are the fields to extract. The Match-Action tables are a series of units that read an input PHV, match certain fields in it using a [[Crossbar switch|crossbar]] and [[Content-addressable memory|CAM memory]], the result is a wide instruction that operates on one or more fields of the PHV and data to support this instruction. The output PHV is then sent to the next MA stage or to the deparser. The deparser takes in the PHV as well as the original packet and its metadata (to fill in missing bits that weren't extracted into the PHV) and then outputs the modified packet as chunks. It's typically programmable as with the parser and may reuse some of the configuration files.

FlexNIC<ref>{{Cite book |last1=Kaufmann |first1=Antoine |last2=Peter |first2=SImon |last3=Sharma |first3=Naveen Kr. |last4=Anderson |first4=Thomas |last5=Krishnamurthy |first5=Arvind |title=Proceedings of the Twenty-First International Conference on Architectural Support for Programming Languages and Operating Systems |chapter=High Performance Packet Processing with FlexNIC |date=2016-03-25 |series=ASPLOS '16 |location=New York, NY, USA |publisher=Association for Computing Machinery |pages=67–81 |doi=10.1145/2872362.2872367 |isbn=978-1-4503-4091-5|s2cid=9625891 |doi-access=free }}</ref> attempts to apply this model to [[Network interface controller|Network Interface Controllers]] allowing servers to send and receive packets at high speeds while maintaining protocol flexibility and without increasing the CPU overhead.

==Generic functions==
In the generic role as a packet processor, a number of optimised features or functions are typically present in a network processor, which include:

* Pattern matching – the ability to find specific patterns of bits or bytes within packets in a packet stream.
* Key lookup – the ability to quickly undertake a database lookup using a key (typically an address in a packet) to find a result, typically [[routing]] information.
* Computation
* Data bitfield manipulation – the ability to change certain data fields contained in the packet as it is being processed.
* [[Queue (data structure)|Queue]] management – as packets are received, processed and scheduled to be sent onwards, they are stored in queues.
* Control processing – the micro operations of processing a packet are controlled at a macro level which involves communication and orchestration with other nodes in a system.
* Quick allocation and re-circulation of packet buffers.

==Architectural paradigms==
In order to deal with high data-rates, several architectural paradigms are commonly used:

* [[CPU pipeline|Pipeline]] of processors - each stage of the pipeline consisting of a processor performing one of the functions listed above.
* [[Parallel computing|Parallel processing]] with multiple processors, often including [[Multithreading (computer architecture)|multithreading]].
* Specialized [[microcode]]d engines to more efficiently accomplish the tasks at hand.
* With the advent of [[Multi-core (computing)|multicore]] architectures, network processors can be used for higher layer ([[OSI model|L4-L7]]) processing.

Additionally, traffic management, which is a critical element in [[OSI model#Layer 2: Data link layer|L2]]-[[OSI model#Layer 3: Network layer|L3]] network processing and used to be executed by a variety of co-processors, has become an integral part of the network processor architecture, and a substantial part of its silicon area ("real estate") is devoted to the integrated traffic manager.<ref>{{Cite book|url=http://www.cse.bgu.ac.il/npbook/|title=Network Processors: Architecture, Programming, and Implementation|last=Giladi|first=Ran|publisher=Morgan Kaufmann|year=2008|isbn=978-0-12-370891-5|series=Systems on Silicon}}</ref> Modern network processors are also equipped with low-latency high-throughput on-chip interconnection networks optimized for the exchange of small messages among cores (few data words). Such networks can be used as an alternative facility for the efficient inter-core communication aside of the standard use of shared memory.<ref>{{cite conference|last1=Buono|first1=Daniele|last2=Mencagli|first2=Gabriele|date=21–25 July 2014|title=Run-time mechanisms for fine-grained parallelism on network processors: The TILEPro64 experience|url=http://pages.di.unipi.it/mencagli/publications/preprint-hpcs-2014.pdf|url-status=live|conference=2014 International Conference on High Performance Computing Simulation (HPCS 2014)|location=Bologna, Italy|pages=55–64|doi=10.1109/HPCSim.2014.6903669|isbn=978-1-4799-5313-4|archive-url=https://web.archive.org/web/20190327010533/http://pages.di.unipi.it/mencagli/publications/preprint-hpcs-2014.pdf|archive-date=27 March 2019}} [https://archive.org/details/RunTimeMechanismsForFineGrainedParallelism Alt URL]</ref>

==Applications==
Using the generic function of the network processor, a software program implements an application that the network processor executes, resulting in the piece of physical equipment performing a task or providing a service. Some of the applications types typically implemented as software running on network processors are:<ref>{{Cite book|title=Network Systems Design Using Network Processors: Intel 2XXX Version|last=Comer|first=Douglas E.|publisher=Addison-Wesley|year=2005|isbn=978-0-13-187286-8}}</ref>

* [[Packet (information technology)|Packet]] or [[Stack frame|frame]] discrimination and forwarding, that is, the basic operation of a [[Router (computing)|router]] or [[Network switch|switch]].
* [[Quality of service]] (QoS) enforcement – identifying different types or classes of packets and providing preferential treatment for some types or classes of packet at the expense of other types or classes of packet.
* Access Control functions – determining whether a specific packet or stream of packets should be allowed to traverse the piece of network equipment.
* [[Encryption]] of data streams – built in hardware-based encryption engines allow individual data flows to be encrypted by the processor.
* [[TCP Offload Engine|TCP offload]] processing

==See also==
* [[Content processor]]
* [[Multi-core processor]]
* [[Knowledge-based processor]]
* [[Active networking]]
* [[Computer engineering]]
* [[Internet]]
* [[List of defunct network processor companies]]
* [[Network Processing Forum]]
* [[Queueing theory]]
* [[Network on a chip]]
* [[Network interface controller]]

==References==
{{Reflist}}

{{CPU technologies}}
{{Hardware acceleration}}
{{Authority control}}

[[Category:Embedded microprocessors]]
[[Category:Network on a chip]]
[[Category:Networking hardware]]
[[Category:Hardware acceleration]]
[[Category:Application-specific integrated circuits]]
[[Category:System on a chip]]