Connection-oriented Ethernet
Encyclopedia
Connection-oriented Ethernet refers to the transformation of Ethernet
, a connectionless communication system by design, into a connection-oriented system. The aim of connection-oriented Ethernet is to create a networking technology that combines the flexibility and cost-efficiency of Ethernet with the reliability of connection-oriented protocols. Connection-oriented Ethernet is used in commercial carrier grade
networks.
. Switched data transport networks are different, as they offer new and different services based on features as statistical multiplexing
and complex connectivity schemes (any point to any point).
Moreover packet transport equipment which makes the ‘machinery’ of data networking, leaving most of the ‘carrier-grade’ qualities such as quality of service
, routing, provisioning, and security, to be realized by packet processing. Addressing these needs in a cost-efficient way is the challenge of all packet-based technologies as next-generation network services emerge and converge over packet-based transport solutions (such as the Internet).
The IP-MPLS
approach aims at providing guaranteed services over the Internet Protocol using a multitude of networking protocols to create, maintain and handle packet data streams. While this approach solves the problem, it inevitably also creates a great deal of complexity as well as poor network utilization.
This brought about the emergence of connection-oriented Ethernet which includes a variety of methodologies to utilize Ethernet for the same functionalities otherwise based on extensive IP protocols. The challenge of carrier Ethernet is to add carrier-grade functionality to Ethernet equipment without losing the cost-effectiveness and simplicity that made it attractive in the first place.
To meet this challenge, common (mainly IEEE 802.1ah
/PBT and T-MPLS
) connection-oriented Ethernet solutions have chosen to rid themselves of the ‘complex’ parts of packet transport to achieve stability and control.
). It defines methods to emulate connection-oriented networks by providing "nailed-up" trunks through a packet-switched network. Key data-plane differences from PBB include the static configuration of forwarding tables within Ethernet switches, dropping of multicast packets and the prevention of "flooding" of frames to unknown destination addresses. Configuration is performed by a centralized management server like in SDH networks, though in the future a control plane may be added. PBT has been presented to IEEE802 and a new project has been approved to standardize it under the name of Provider Backbone Bridge Traffic Engineering (PBB-TE) (IEEE 802.1Qay), a modification to PBB.
Provider Backbone Bridges (PBB) is an Ethernet data-plane technology invented in 2004 by Nortel Networks (now Avaya
). It is sometimes known as MAC-in-MAC because it involves encapsulating an Ethernet datagram inside another one with new source and destination addresses (termed B-SA and B-DA). IEEE802 is standardizing the technology as (IEEE 802.1ah
), currently under development. PBB is the original data-plane chosen by British Telecom for their new PBT-based Ethernet transport.
PBB can support point-to-point, point-to-multipoint and multipoint-to-multipoint networks. PBT focuses on point-to-point connectivity, and may be capable of extension to point-to-multipoint, a key technology for advanced data applications such as IPTV. PBT avoids trying to address multipoint-to-multipoint networking, as in the opinion of some of its supporters guaranteed levels of service in multipoint-to-multipoint networks are impossible.
Additionally Ethernet is being reinforced with operations, administration, and maintenance
(OAM) capabilities through the work of various standard bodies (IEEE 802.1ag, ITU-T Y.1731 and G.8021, IEEE 802.3ah).
PBT/PBB equipment leverages economies of scale inherent in Ethernet promising about 30%–40% cheaper solutions compared to T-MPLS equipment with identical features and capabilities making PBT a better overall return on investment.
, as its name implies, is a derivative of MPLS
that renounces all MPLS signaling features and, like PBT, uses a centralized control-plane to perform routing and traffic engineering. T-MPLS is currently being standardized only at ITU-T and enjoys strong vendor support but little carrier support.
As a native MPLS derivative, T-MPLS can be easily implemented over existing MPLS routers. However, T-MPLS has been stripped of the characteristics which originally made it attractive to carriers—control-plane automation, signaling, and QoS—and therefore has yet to prove its benefits for the transport network. T-MPLS OAM, defined in ITU Y.1711, is different from MPLS OAM and lacks powerful management tools that carriers typically expect.
(CIR) and Excess Information Rate (EIR). A CIR service guarantees its user a fixed amount of bandwidth, whereas an EIR service offers best-effort only transport. Both types of services share a single capacity-constrained infrastructure. Both are further defined by additional parameters.
A carrier's return on investment
is directly related to its ability to transport more service instances over a fixed capacity-constrained infrastructure, keeping Quality of Service high. It is further associated with its ability to offer a broad range of added-value services, such as IPTV, Voice, and VPN, whose requirements can widely vary and pose technical difficulties when sharing the same infrastructure.
With the above in mind, the carrier's objective is to offer a maximum amount of best-effort EIR services over its network while reliably serving its committed CIR services. To achieve this PBB/PBT and T-MPLS approaches largely under-provision network resources, in order to avoid a situation where a burst in best-effort traffic would jeopardize the ability to serve committed traffic, leading to costly penalties. An additional issue with best-effort access on data networks is fair allocation among clients. With PBB/PBT and T-MPLS, the amount of bandwidth available to a particular client greatly depends on the client's location and the prevailing traffic conditions. This limits the value customers attach to EIR services and undercuts carriers' opportunities to offer differentiated access to its excess capacity.
Performing traffic engineering in real-time is thus key to next-generation Ethernet transport. Additional qualities are required to make Ethernet a carrier-grade technology:
Multi-vendor support, the ability to support a variety of Ethernet switches in the core, is a desirable attribute as it allows carriers to use inexpensive switches to build their metro transport network. Vendors such as Tejas Networks, Ethos Networks, and Nortel
offer solutions which meet the above requirements, yet preserve Ethernet's simplicity and flexibility.
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
, a connectionless communication system by design, into a connection-oriented system. The aim of connection-oriented Ethernet is to create a networking technology that combines the flexibility and cost-efficiency of Ethernet with the reliability of connection-oriented protocols. Connection-oriented Ethernet is used in commercial carrier grade
Carrier grade
In telecommunication, a "carrier grade" or "carrier class" refers to a system, or a hardware or software component that is extremely reliable, well tested and proven in its capabilities...
networks.
Background
Traditional carrier networks deliver services at very high availabilityHigh availability
High availability is a system design approach and associated service implementation that ensures a prearranged level of operational performance will be met during a contractual measurement period....
. Switched data transport networks are different, as they offer new and different services based on features as statistical multiplexing
Statistical multiplexing
Statistical multiplexing is a type of communication link sharing, very similar to dynamic bandwidth allocation . In statistical multiplexing, a communication channel is divided into an arbitrary number of variable bit-rate digital channels or data streams. The link sharing is adapted to the...
and complex connectivity schemes (any point to any point).
Moreover packet transport equipment which makes the ‘machinery’ of data networking, leaving most of the ‘carrier-grade’ qualities such as quality of service
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
, routing, provisioning, and security, to be realized by packet processing. Addressing these needs in a cost-efficient way is the challenge of all packet-based technologies as next-generation network services emerge and converge over packet-based transport solutions (such as the Internet).
The IP-MPLS
Mpls
MPLS or Mpls can refer to:* Minneapolis, Minnesota, United States* Multiprotocol Label Switching, a data-carrying mechanism in computer networking...
approach aims at providing guaranteed services over the Internet Protocol using a multitude of networking protocols to create, maintain and handle packet data streams. While this approach solves the problem, it inevitably also creates a great deal of complexity as well as poor network utilization.
This brought about the emergence of connection-oriented Ethernet which includes a variety of methodologies to utilize Ethernet for the same functionalities otherwise based on extensive IP protocols. The challenge of carrier Ethernet is to add carrier-grade functionality to Ethernet equipment without losing the cost-effectiveness and simplicity that made it attractive in the first place.
To meet this challenge, common (mainly IEEE 802.1ah
IEEE 802.1ah
Provider Backbone Bridges is a set of architecture and protocols for routing over a provider's network allowing interconnection of multiple Provider Bridge Networks without losing each customer's individually defined VLANs. It was initially created by Nortel before being submitted to the IEEE...
/PBT and T-MPLS
T-MPLS
T-MPLS or Transport MPLS is a transport network layer technology that uses extensions to a subset of the existing MPLS standards and is designed specifically for application in transport networks. Work to define T-MPLS was started by the ITU-T in February 2006...
) connection-oriented Ethernet solutions have chosen to rid themselves of the ‘complex’ parts of packet transport to achieve stability and control.
PBT and PBB
Provider Backbone Transport (PBT) is connection-oriented switch operation scheme and network management architecture. PBT was invented by British Telecom (BT) and developed by Nortel (now AvayaAvaya
Avaya Inc. is a privately held computer networking, information technology and telecommunications company that is a global provider of business communications systems. The international head quarters is in Basking Ridge, New Jersey, United States...
). It defines methods to emulate connection-oriented networks by providing "nailed-up" trunks through a packet-switched network. Key data-plane differences from PBB include the static configuration of forwarding tables within Ethernet switches, dropping of multicast packets and the prevention of "flooding" of frames to unknown destination addresses. Configuration is performed by a centralized management server like in SDH networks, though in the future a control plane may be added. PBT has been presented to IEEE802 and a new project has been approved to standardize it under the name of Provider Backbone Bridge Traffic Engineering (PBB-TE) (IEEE 802.1Qay), a modification to PBB.
Provider Backbone Bridges (PBB) is an Ethernet data-plane technology invented in 2004 by Nortel Networks (now Avaya
Avaya
Avaya Inc. is a privately held computer networking, information technology and telecommunications company that is a global provider of business communications systems. The international head quarters is in Basking Ridge, New Jersey, United States...
). It is sometimes known as MAC-in-MAC because it involves encapsulating an Ethernet datagram inside another one with new source and destination addresses (termed B-SA and B-DA). IEEE802 is standardizing the technology as (IEEE 802.1ah
IEEE 802.1ah
Provider Backbone Bridges is a set of architecture and protocols for routing over a provider's network allowing interconnection of multiple Provider Bridge Networks without losing each customer's individually defined VLANs. It was initially created by Nortel before being submitted to the IEEE...
), currently under development. PBB is the original data-plane chosen by British Telecom for their new PBT-based Ethernet transport.
PBB can support point-to-point, point-to-multipoint and multipoint-to-multipoint networks. PBT focuses on point-to-point connectivity, and may be capable of extension to point-to-multipoint, a key technology for advanced data applications such as IPTV. PBT avoids trying to address multipoint-to-multipoint networking, as in the opinion of some of its supporters guaranteed levels of service in multipoint-to-multipoint networks are impossible.
Additionally Ethernet is being reinforced with operations, administration, and maintenance
OA&M
Operations, administration and management or operations, administration and maintenance is a general term used to describe the processes, activities, tools, standards, etc involved with operating, administering, managing and maintaining any system...
(OAM) capabilities through the work of various standard bodies (IEEE 802.1ag, ITU-T Y.1731 and G.8021, IEEE 802.3ah).
PBT/PBB equipment leverages economies of scale inherent in Ethernet promising about 30%–40% cheaper solutions compared to T-MPLS equipment with identical features and capabilities making PBT a better overall return on investment.
T-MPLS (Transport MPLS)
T-MPLST-MPLS
T-MPLS or Transport MPLS is a transport network layer technology that uses extensions to a subset of the existing MPLS standards and is designed specifically for application in transport networks. Work to define T-MPLS was started by the ITU-T in February 2006...
, as its name implies, is a derivative of MPLS
Mpls
MPLS or Mpls can refer to:* Minneapolis, Minnesota, United States* Multiprotocol Label Switching, a data-carrying mechanism in computer networking...
that renounces all MPLS signaling features and, like PBT, uses a centralized control-plane to perform routing and traffic engineering. T-MPLS is currently being standardized only at ITU-T and enjoys strong vendor support but little carrier support.
As a native MPLS derivative, T-MPLS can be easily implemented over existing MPLS routers. However, T-MPLS has been stripped of the characteristics which originally made it attractive to carriers—control-plane automation, signaling, and QoS—and therefore has yet to prove its benefits for the transport network. T-MPLS OAM, defined in ITU Y.1711, is different from MPLS OAM and lacks powerful management tools that carriers typically expect.
Achieving the promise of carrier-grade Ethernet
Services in the data network are typically classified into 2 major categories: Committed Information RateCommitted Information Rate
Committed information rate or CIR in a Frame relay network is the average bandwidth for a virtual circuit guaranteed by an ISP to work under normal conditions. At any given time, the bandwidth should not fall below this committed figure...
(CIR) and Excess Information Rate (EIR). A CIR service guarantees its user a fixed amount of bandwidth, whereas an EIR service offers best-effort only transport. Both types of services share a single capacity-constrained infrastructure. Both are further defined by additional parameters.
A carrier's return on investment
Return on investment
Return on investment is one way of considering profits in relation to capital invested. Return on assets , return on net assets , return on capital and return on invested capital are similar measures with variations on how “investment” is defined.Marketing not only influences net profits but also...
is directly related to its ability to transport more service instances over a fixed capacity-constrained infrastructure, keeping Quality of Service high. It is further associated with its ability to offer a broad range of added-value services, such as IPTV, Voice, and VPN, whose requirements can widely vary and pose technical difficulties when sharing the same infrastructure.
With the above in mind, the carrier's objective is to offer a maximum amount of best-effort EIR services over its network while reliably serving its committed CIR services. To achieve this PBB/PBT and T-MPLS approaches largely under-provision network resources, in order to avoid a situation where a burst in best-effort traffic would jeopardize the ability to serve committed traffic, leading to costly penalties. An additional issue with best-effort access on data networks is fair allocation among clients. With PBB/PBT and T-MPLS, the amount of bandwidth available to a particular client greatly depends on the client's location and the prevailing traffic conditions. This limits the value customers attach to EIR services and undercuts carriers' opportunities to offer differentiated access to its excess capacity.
Performing traffic engineering in real-time is thus key to next-generation Ethernet transport. Additional qualities are required to make Ethernet a carrier-grade technology:
- Rich OAM: capacity optimization, path calculation and configuration, iterative optimization.
- Path protection: sub-50ms failover.
- Support for next-generation services: efficient provisioning of point-to-multipoint and multipoint-to-multipoint services.
Multi-vendor support, the ability to support a variety of Ethernet switches in the core, is a desirable attribute as it allows carriers to use inexpensive switches to build their metro transport network. Vendors such as Tejas Networks, Ethos Networks, and Nortel
Nortel
Nortel Networks Corporation, formerly known as Northern Telecom Limited and sometimes known simply as Nortel, was a multinational telecommunications equipment manufacturer headquartered in Mississauga, Ontario, Canada...
offer solutions which meet the above requirements, yet preserve Ethernet's simplicity and flexibility.
See also
- Provider Backbone Bridges
- Provider Backbone Bridge Traffic EngineeringProvider Backbone Bridge Traffic EngineeringProvider Backbone Bridge Traffic Engineering is an approved telecommunications networking standard, IEEE 802.1Qay-2009. PBB-TE adapts Ethernet technology to carrier class transport networks...
- Carrier EthernetCarrier EthernetCarrier Ethernet is a marketing term for extensions to Ethernet to enable telecommunications network providers to provide Ethernet services to customers and to utilize Ethernet technology in their networks....
- Metro EthernetMetro EthernetA Metro Ethernet is a computer network that covers a metropolitan area and that is based on the Ethernet standard. It is commonly used as a metropolitan access network to connect subscribers and businesses to a larger service network or the Internet...
- IEEE 802.1IEEE 802.1IEEE 802.1 is a working group of the IEEE 802 project of the IEEE Standards Association.It is concerned with:* 802 LAN/MAN architecture* internetworking among 802 LANs, MANs and other wide area networks* 802 Link Security* 802 overall network management...
- 802.1aq Shortest Path BridgingIEEE 802.1aq802.1aq Shortest Path Bridging or SPB in computer networking is a technology that greatly simplifies the creation and configuration of carrier, enterprise, and cloud networks which virtually eliminates human error, while enabling multipath routing...
- IEEE 802.1ah-2008 Provider Backbone Bridges