Fractional lambda switching
Encyclopedia
Fractional lambda switching (FλS) leverages on time-driven switching
(TDS
) to realize sub-lambda switching in highly scalable dynamic optical networking, which requires minimum (possibly optical) buffers. Fractional lambda switching implies switching fractions of optical channels as opposed to whole lambda switching where whole optical channels are the switching unit. In this context, TDS has the same general objectives as optical burst switching
and optical packet switching: realizing all-optical networks with high wavelength utilization. TDS operation is based on time frames (TFs) that can be viewed as virtual containers for multiple IP
packets that are switched at every TDS switch based on and coordinated by the UTC (coordinated universal time
) signal implementing pipeline forwarding
. In the context of optical networks, synchronous virtual pipe
s SVPs
typical of pipeline forwarding
are called fractional lambda pipes (FλPs).
In FλS, likewise in TDS, all packets in the same time frame are switched in the same way. Consequently, header processing is not required, which results in low complexity (hence high scalability) and enables optical implementation . The TF is the basic SVP
capacity allocation unit; hence, the allocation granularity depends on the number of TFs per time cycle. For example, with a 10 Gb/s optical channel and 1000 TFs in each time cycle, the minimum FλP capacity (obtained by allocating one TF in every time cycle) is 10 Mb/s.
Scheduling through a switching fabric is based on a pre-defined schedule, which enables the implementation of a simple controller. Moreover, low-complexity switching fabric architectures, such as Banyan, can be deployed notwithstanding their blocking features, thus further enhancing scalability. In fact, blocking can be avoided during schedule computation by avoiding conflicting input/output connections during the same TF. Several results show that (especially if multiple wavelength division multiplexing channels are deployed on optical links between fractional λ switches) high link utilization can be achieved with negligible blocking using a Banyan network without speedup .
Various aspects of the technology are covered by several patents issued by both the United States Patent and Trademark Office
and the European Patent Office
.
Time-driven switching
In Telecommunication and Computer networking, Time-Driven Switching is a node by node time variant implementation of Circuit switching, where the propagating datagram is shorter in space than the distance between source and destination...
(TDS
Time-driven switching
In Telecommunication and Computer networking, Time-Driven Switching is a node by node time variant implementation of Circuit switching, where the propagating datagram is shorter in space than the distance between source and destination...
) to realize sub-lambda switching in highly scalable dynamic optical networking, which requires minimum (possibly optical) buffers. Fractional lambda switching implies switching fractions of optical channels as opposed to whole lambda switching where whole optical channels are the switching unit. In this context, TDS has the same general objectives as optical burst switching
Optical burst switching
Optical burst switching is an optical networking technique that allows dynamic sub-wavelength switching of data. OBS is viewed as a compromise between the yet unfeasible full optical packet switching and the mostly static optical circuit switching...
and optical packet switching: realizing all-optical networks with high wavelength utilization. TDS operation is based on time frames (TFs) that can be viewed as virtual containers for multiple IP
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
packets that are switched at every TDS switch based on and coordinated by the UTC (coordinated universal time
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
) signal implementing pipeline forwarding
Pipeline forwarding
Pipeline forwarding applies to packet forwarding in computer networks the basic concept of pipelining, which has been widely and successfully used in computing — specifically, in the architecture of all major central processing units — and manufacturing — specifically in assembly lines of...
. In the context of optical networks, synchronous virtual pipe
Synchronous virtual pipe
When realizing pipeline forwarding a predefined schedule for forwarding a pre-allocated amount of bytes during one or more time frames along a path of subsequent switches establishes a synchronous virtual pipe . The SVP capacity is determined by the total number of bits allocated in every time...
s SVPs
Synchronous virtual pipe
When realizing pipeline forwarding a predefined schedule for forwarding a pre-allocated amount of bytes during one or more time frames along a path of subsequent switches establishes a synchronous virtual pipe . The SVP capacity is determined by the total number of bits allocated in every time...
typical of pipeline forwarding
Pipeline forwarding
Pipeline forwarding applies to packet forwarding in computer networks the basic concept of pipelining, which has been widely and successfully used in computing — specifically, in the architecture of all major central processing units — and manufacturing — specifically in assembly lines of...
are called fractional lambda pipes (FλPs).
In FλS, likewise in TDS, all packets in the same time frame are switched in the same way. Consequently, header processing is not required, which results in low complexity (hence high scalability) and enables optical implementation . The TF is the basic SVP
Synchronous virtual pipe
When realizing pipeline forwarding a predefined schedule for forwarding a pre-allocated amount of bytes during one or more time frames along a path of subsequent switches establishes a synchronous virtual pipe . The SVP capacity is determined by the total number of bits allocated in every time...
capacity allocation unit; hence, the allocation granularity depends on the number of TFs per time cycle. For example, with a 10 Gb/s optical channel and 1000 TFs in each time cycle, the minimum FλP capacity (obtained by allocating one TF in every time cycle) is 10 Mb/s.
Scheduling through a switching fabric is based on a pre-defined schedule, which enables the implementation of a simple controller. Moreover, low-complexity switching fabric architectures, such as Banyan, can be deployed notwithstanding their blocking features, thus further enhancing scalability. In fact, blocking can be avoided during schedule computation by avoiding conflicting input/output connections during the same TF. Several results show that (especially if multiple wavelength division multiplexing channels are deployed on optical links between fractional λ switches) high link utilization can be achieved with negligible blocking using a Banyan network without speedup .
Various aspects of the technology are covered by several patents issued by both the United States Patent and Trademark Office
United States Patent and Trademark Office
The United States Patent and Trademark Office is an agency in the United States Department of Commerce that issues patents to inventors and businesses for their inventions, and trademark registration for product and intellectual property identification.The USPTO is based in Alexandria, Virginia,...
and the European Patent Office
European Patent Office
The European Patent Office is one of the two organs of the European Patent Organisation , the other being the Administrative Council. The EPO acts as executive body for the Organisation while the Administrative Council acts as its supervisory body as well as, to a limited extent, its legislative...
.