Pseudowire

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In computer networking and telecommunications, a pseudowire (or pseudo-wire) is an emulation of a point-to-point connection over a packet-switched network (PSN).

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A pseudowire in networking is a way to emulate a physical wire across a packet-switched network. Essentially, it lets two endpoints feel as if they’re directly connected by a traditional wire (like a T1 line or Ethernet link), even though the data is actually traveling over a more complex network, such as an IP or MPLS (Multiprotocol Label Switching) network.

Here's a breakdown of how pseudowires work:

Purpose: Pseudowires allow service providers to offer traditional network services (like Ethernet, TDM, ATM, or Frame Relay) across modern packet-switched networks. This means they can use a flexible IP or MPLS network instead of dedicated circuits, saving on infrastructure costs.

Encapsulation: Data from one type of network (like Ethernet) is encapsulated into packets that can be transported across an IP/MPLS network. This process packages the original data, keeping its format, and adds labels or headers that tell the network where to send the packets.

Endpoints: A pseudowire has two endpoints, one at each "end" of the emulated wire. The devices at these endpoints are responsible for encapsulating and de-encapsulating the data, so it appears as if it’s coming from a point-to-point link.

Use Cases: Some typical uses for pseudowires include extending Ethernet networks across cities, linking data centers, and allowing legacy systems (like older phone networks) to work over newer infrastructure without major upgrades.

Benefits: Pseudowires make it easy to extend traditional services over more efficient, flexible networks. They also allow a single network infrastructure to carry various service types, improving operational efficiency and scalability for network providers.

In simple terms, a pseudowire is like a virtual tunnel that tricks two points in the network into thinking they’re connected by a direct wire, even though they’re actually communicating over a more complex infrastructure.

The pseudowire emulates the operation of a "transparent wire" carrying the service, but it is realized that this emulation will rarely be perfect. The service being carried over the "wire" may be Asynchronous Transfer Mode (ATM), Frame Relay, Ethernet or time-division multiplexing (TDM) while the packet network may be Multiprotocol Label Switching (MPLS), Internet Protocol (IPv4 or IPv6), or Layer 2 Tunneling Protocol Version 3 (L2TPv3).

The first pseudowire specifications were the Martini draft for ATM pseudowires, and the TDMoIP draft for transport of E1/T1 over IP. [1]

In 2001, the Internet Engineering Task Force (IETF) set up the PWE3 working group, which was chartered to develop an architecture for service provider edge-to-edge pseudowires, and service-specific documents detailing the encapsulation techniques. Other standardization forums, including the International Telecommunication Union (ITU) and the MFA Forum, are also active in producing standards and implementation agreements for pseudowires.

Starting from 2006, telecom operators like BellSouth, Supercomm, AT&T, and Verizon began to invest more into pseudowire technology, pointing out its advantages to Ethernet in particular. [2] Pseudowires tie services together across multiple transport technologies, including Ethernet over SONET, WDM, GPON, DSL, and WiMax. Over the next decade, the technology became mainstream.

In 2017 Cisco published a comprehensive document explaining the concept, troubleshooting, and configuration details for all Cisco equipment pieces, which supported pseudowire. [3] Today, the service is provided by a number of telecommunication companies like Axerra Networks, MCI Inc, or by Infrastructure as a service providers like Voxility. [4]

There are now many pseudowire standards, the most important of which are IETF RFCs as well as ITU-T Recommendations:

RFCs

ITU-T Recommendations

See also

Related Research Articles

<span class="mw-page-title-main">Asynchronous Transfer Mode</span> Digital telecommunications protocol for voice, video, and data

Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by the American National Standards Institute and International Telecommunication Union Telecommunication Standardization Sector for digital transmission of multiple types of traffic. ATM was developed to meet the needs of the Broadband Integrated Services Digital Network as defined in the late 1980s, and designed to integrate telecommunication networks. It can handle both traditional high-throughput data traffic and real-time, low-latency content such as telephony (voice) and video. ATM provides functionality that uses features of circuit switching and packet switching networks by using asynchronous time-division multiplexing. ATM was seen in the 1990s as a competitor to Ethernet and networks carrying IP traffic as, unlike Ethernet, it was faster and designed with quality-of-service in mind, but it fell out of favor once Ethernet reached speeds of 1 gigabits per second.

Multiprotocol Label Switching (MPLS) is a routing technique in telecommunications networks that directs data from one node to the next based on labels rather than network addresses. Whereas network addresses identify endpoints, the labels identify established paths between endpoints. MPLS can encapsulate packets of various network protocols, hence the multiprotocol component of the name. MPLS supports a range of access technologies, including T1/E1, ATM, Frame Relay, and DSL.

<span class="mw-page-title-main">Wide area network</span> Computer network that connects devices across a large distance and area

A wide area network (WAN) is a telecommunications network that extends over a large geographic area. Wide area networks are often established with leased telecommunication circuits.

<span class="mw-page-title-main">Frame Relay</span> Wide area network technology

Frame Relay is a standardized wide area network (WAN) technology that specifies the physical and data link layers of digital telecommunications channels using a packet switching methodology. Originally designed for transport across Integrated Services Digital Network (ISDN) infrastructure, it may be used today in the context of many other network interfaces.

A frame is a digital data transmission unit in computer networking and telecommunications. In packet switched systems, a frame is a simple container for a single network packet. In other telecommunications systems, a frame is a repeating structure supporting time-division multiplexing.

A virtual circuit (VC) is a means of transporting data over a data network, based on packet switching and in which a connection is first established across the network between two endpoints. The network, rather than having a fixed data rate reservation per connection as in circuit switching, takes advantage of the statistical multiplexing on its transmission links, an intrinsic feature of packet switching.

The Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol for encapsulating Point-to-Point Protocol (PPP) frames inside Ethernet frames. It appeared in 1999, in the context of the boom of DSL as the solution for tunneling packets over the DSL connection to the ISP's IP network, and from there to the rest of the Internet. A 2005 networking book noted that "Most DSL providers use PPPoE, which provides authentication, encryption, and compression." Typical use of PPPoE involves leveraging the PPP facilities for authenticating the user with a username and password, via the PAP protocol or via CHAP. PAP was dominant in 2007 but service providers have been transitioning to the more secure CHAP, because PAP is a plain-text protocol. Around 2000, PPPoE was also starting to become a replacement method for talking to a modem connected to a computer or router over an Ethernet LAN displacing the older method, which had been USB. This use-case, connecting routers to modems over Ethernet is still extremely common today.

In computer networking and telecommunications, TDM over IP (TDMoIP) is the emulation of time-division multiplexing (TDM) over a packet-switched network (PSN). TDM refers to a T1, E1, T3 or E3 signal, while the PSN is based either on IP or MPLS or on raw Ethernet. A related technology is circuit emulation, which enables transport of TDM traffic over cell-based (ATM) networks.

MPLS VPN is a family of methods for using Multiprotocol Label Switching (MPLS) to create virtual private networks (VPNs). MPLS VPN is a flexible method to transport and route several types of network traffic using an MPLS backbone.

<span class="mw-page-title-main">ATM Forum</span> Industry consortium to promote Asynchronous Transfer Mode technology

The ATM Forum was founded in 1991 to be the industry consortium to promote Asynchronous Transfer Mode technology used in telecommunication networks; the founding president and chairman was Fred Sammartino of Sun Microsystems. It was a non-profit international organization. The ATM Forum created over 200 implementation agreements.

<span class="mw-page-title-main">Broadband remote access server</span>

A broadband remote access server routes traffic to and from broadband remote access devices such as digital subscriber line access multiplexers (DSLAM) on an Internet service provider's (ISP) network. BRAS can also be referred to as a broadband network gateway or border network gateway (BNG).

The next-generation network (NGN) is a body of key architectural changes in telecommunication core and access networks. The general idea behind the NGN is that one network transports all information and services by encapsulating these into IP packets, similar to those used on the Internet. NGNs are commonly built around the Internet Protocol, and therefore the term all IP is also sometimes used to describe the transformation of formerly telephone-centric networks toward NGN.

<span class="mw-page-title-main">Metro Ethernet</span> Metropolitan area network based on Ethernet standards

A metropolitan-area Ethernet, Ethernet MAN, carrier Ethernet or metro Ethernet network is a metropolitan area network (MAN) that is based on Ethernet standards. It is commonly used to connect subscribers to a larger service network or for internet access. Businesses can also use metropolitan-area Ethernet to connect their own offices to each other.

In telecommunications and computer networking, connection-oriented communication is a communication protocol where a communication session or a semi-permanent connection is established before any useful data can be transferred. The established connection ensures that data is delivered in the correct order to the upper communication layer. The alternative is called connectionless communication, such as the datagram mode communication used by Internet Protocol (IP) and User Datagram Protocol (UDP), where data may be delivered out of order, since different network packets are routed independently and may be delivered over different paths.

In computer networking, an edge device is a device that provides an entry point into enterprise or service provider core networks. Examples include routers, routing switches, integrated access devices (IADs), multiplexers, and a variety of metropolitan area network (MAN) and wide area network (WAN) access devices. Edge devices also provide connections into carrier and service provider networks. An edge device that connects a local area network to a high speed switch or backbone may be called an edge concentrator.

In 2001, the IETF set up the Pseudowire Emulation Edge to Edge working group, and this group was given the initialism PWE3. The working group was chartered to develop an architecture for service provider edge-to-edge pseudowires and service-specific documents detailing the encapsulation techniques.

Virtual leased lines (VLL), also referred to as virtual private wire service (VPWS) or EoMPLS, is a way to provide Ethernet-based point to point communication over Multiprotocol Label Switching (MPLS) or Internet Protocol networks. VLL uses the pseudo-wire encapsulation for transporting Ethernet traffic over an MPLS tunnel across an MPLS backbone. VLL also describes a point to point bonded connection using the broadband bonding technology.

A forwarding information base (FIB), also known as a forwarding table or MAC table, is most commonly used in network bridging, routing, and similar functions to find the proper output network interface controller to which the input interface should forward a packet. It is a dynamic table that maps MAC addresses to ports. It is the essential mechanism that separates network switches from Ethernet hubs. Content-addressable memory (CAM) is typically used to efficiently implement the FIB, thus it is sometimes called a CAM table.

Circuit emulation service (CES) is a telecommunication technology used to send information over asynchronous data networks like ATM, Ethernet or MPLS, so that it is received error-free with constant delay, similar to a leased line.

<span class="mw-page-title-main">Provider-provisioned VPN</span>

A provider-provisioned VPN (PPVPN) is a virtual private network (VPN) implemented by a connectivity service provider or large enterprise on a network they operate on their own, as opposed to a "customer-provisioned VPN" where the VPN is implemented by the customer who acquires the connectivity service on top of the technical specificities of the provider.

References

  1. ↑ Minoli, Daniel (17 June 2013), Building the Internet of Things with IPv6 and MIPv6, John Wiley & Sons, ISBN   978-1118647134, OCLC   851158445 , retrieved 2020-02-23.
  2. ↑ "Carriers eye pseudowires for service delivery". Lightwave. January 2006. Retrieved 23 February 2020.
  3. ↑ "Pseudowire Concepts and troubleshooting". Cisco. Retrieved 23 February 2020.
  4. ↑ "Axerra Networks". CBInsights. Retrieved 23 February 2020.
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