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Mansa Musa was the ruler of the Mali Empire in West Africa. Details recorded here should be sourced; unknown information is left blank.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
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A Signal Transfer Point (STP) is a node in an SS7 network that routes signaling messages based on their destination point code in the SS7 network.[1] It works as a router that relays Signalling System No. 7 (SS7) messages between signaling end-points (SEPs) and other signaling transfer points (STPs). Typical SEPs include service switching points (SSPs) and service control points (SCPs). The STP is connected to adjacent SEPs and STPs via signaling links. Based on the address fields of the SS7 messages, the STP routes the messages to the appropriate outgoing signaling link. Edge STPs can also route based upon message body content using deep packet inspection techniques, and can provide address translations and screen content to limit the transfer of messages with dubious content or sent from unreliable sources. To meet stringent reliability requirements, STPs are typically provisioned in mated pairs.
These 'routers' are connected just by signaling links; they do not have users attached (where a user could be a mobile station (MS), a PSTN user in case of a public terrestrial network, or a piece of terminal equipment at the end of an ISDN B channel). SEPs send signaling messages to other SEPs, but the messages are normally routed via the SEP's adjacent STPs. An STP's main function is to identify the best path for two SEPs to communicate. A typical application would be for two SEPs to agree on the use of a shared data path (e.g., using ISUP to initiate a voice call between a user on one SEP and a user on the second SEP). In this way, STPs route signaling messages (for starting, maintaining or finishing any kind of calls originated by the SEPs' attached users) while avoiding disabled intermediary STPs.
A signaling message typically never goes directly from a given SEP to the destination SEP: the message would normally have to pass through the initiating SEP's adjacent STP so that it can be routed to the destination SEP. In some applications, however, SEPs might be directly connected with signaling links; this would typically be done to enhance robustness or performance between two critical SEPs. Such mesh network configurations are also common in Europe, where STPs have not found widespread deployment[citation needed].
In some cases, signaling messages can be originated by the STP to learn about the state of the signaling network. Some examples include:
A given piece of equipment can implement both SEP and STP functionality. This is commonly done in some SSPs. This is also seen in Signaling Gateways that also have Application Server (AS) functionality as defined by the IETF.
Some UMTS number portability solutions are implemented in STPs. In UMTS, the STP provides Global Title Translation (GTT), which may be used to route queries from a gateway MSC (GMSC) to the HLR. Note that for every call to an MS, the call is first routed to the MS's Gateway MSC.
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A Signal Transfer Point (STP) is a node in an SS7 network that routes signaling messages based on their destination point code in the SS7 network. It works as a router that relays Signalling System No. 7 (SS7) messages between signaling end-points (SEPs) and other signaling transfer points (STPs). Typical SEPs include service switching points (SSPs) and service control points (SCPs). The STP is connected to adjacent SEPs and STPs via signaling links. Based on the address fields of the SS7 messages, the STP routes the messages to the appropriate outgoing signaling link. Edge STPs can also route based upon message body content using deep packet inspection techniques, and can provide address translations and screen content to limit the transfer of messages with dubious content or sent from unreliable sources. To meet stringent reliability requirements, STPs are typically provisioned in mated pairs. These 'routers' are connected just by signaling links; they do not have users attached (where a user could be a mobile station (MS), a PSTN user in case of a public terrestrial network, or a piece of terminal equipment at the end of an ISDN B channel). SEPs send signaling messages to other SEPs, but the messages are normally routed via the SEP's adjacent STPs. An STP's main function is to identify the best path for two SEPs to communicate. A typical application would be for two SEPs to agree on the use of a shared data path (e.g., using ISUP to initiate a voice call between a user on one SEP and a user on the second SEP). In this way, STPs route signaling messages (for starting, maintaining or finishing any kind of calls originated by the SEPs' attached users) while avoiding disabled intermediary STPs. A signaling message typically never goes directly from a given SEP to the destination SEP: the message would normally have to pass through the initiating SEP's adjacent STP so that it can be routed to the destination SEP. In some applications, however, SEPs might be directly connected with signaling links; this would typically be done to enhance robustness or performance between two critical SEPs. Such mesh network configurations are also common in Europe, where STPs have not found widespread deployment. In some cases, signaling messages can be originated by the STP to learn about the state of the signaling network. Some examples include: an STP may send route set test messages to probe the availability of a particular SEP; it may send low-level MTP messages to an adjacent signaling point to check the Bit Error Rate (BER) on a particular signaling link; or it may let other adjacent signaling points know that it is going out of service; in this way, the adjacent signaling points will try to avoid this OOS STP. A given piece of equipment can implement both SEP and STP functionality. This is commonly done in some SSPs. This is also seen in Signaling Gateways that also have Application Server (AS) functionality as defined by the IETF. Some UMTS number portability solutions are implemented in STPs. In UMTS, the STP provides Global Title Translation (GTT), which may be used to route queries from a gateway MSC (GMSC) to the HLR. Note that for every call to an MS, the call is first routed to the MS's Gateway MSC.
In telecommunications, a Signaling End Point (SEP) is an SS7 endpoint. This is to be contrasted with a Signal Transfer Point (STP). Examples include: Intelligent Network components such as Service Control Points (SCPs) and Service Switching Points (SSPs) Telephone exchanges implementing Telephone User Part (TUP) or ISDN User Part (ISUP) Mobile Switching Centers implementing MAP
A signaling gateway is a network component responsible for transferring signaling messages (i.e. information related to call establishment, billing, location, short messages, address conversion, and other services) between Common Channel Signaling (CCS) nodes that communicate using different protocols and transports. Transport conversion is often from SS7 to IP. A SIGTRAN Signaling Gateway is a network component that performs packet level translation of signaling from common channel signaling (based upon SS7) to SIGTRAN signaling (based upon IP). The concept of the SIGTRAN signaling gateway was introduced in the IETF document: RFC 2719: Architectural Framework for Signaling Transport. A signaling gateway can be implemented as an embedded component of some other network element, or can be provided as a stand-alone network element. For example: a signaling gateway is often part of a softswitch in modern VoIP deployments. The signaling gateway function can also be included within the larger operational domain of a Signal Transfer Point (STP). Protocol conversion gateways can also convert from one network operational paradigm to another – for example, SIP to ISUP for call control, SIP to TCAP for address translation, or SIP to MAP for location or presence.
In engineering, a transfer function (also known as system function or network function) of a system, sub-system, or component is a mathematical function that models the system's output for each possible input. It is widely used in electronic engineering tools like circuit simulators and control systems and in chemical reaction engineering for the study and modeling of the residence time distribution and stability of a reactor. In simple cases, this function can be represented as a two-dimensional graph of an independent scalar input versus the dependent scalar output (known as a transfer curve or characteristic curve). Transfer functions for components are used to design and analyze systems assembled from components, particularly using the block diagram technique, in electronics and control theory. Dimensions and units of the transfer function model the output response of the device for a range of possible inputs. The transfer function of a two-port electronic circuit, such as an amplifier, might be a two-dimensional graph of the scalar voltage at the output as a function of the scalar voltage applied to the input; the transfer function of an electromechanical actuator might be the mechanical displacement of the movable arm as a function of electric current applied to the device; the transfer function of a photodetector might be the output voltage as a function of the luminous intensity of incident light of a given wavelength. The term transfer function is also used in the frequency domain analysis of systems using transform methods, such as the Laplace transform; it is the amplitude of the output as a function of the frequency of the input signal. The transfer function of an electronic filter is the amplitude at the output as a function of the frequency of a constant amplitude sine wave applied to the input. For optical imaging devices, the optical transfer function is the Fourier transform of the point spread function (a function of spatial frequency).
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.