This document defines the forwarding element (FE) model used in the Forwarding and Control Element Separation (ForCES) protocol. The model represents the capabilities, state, and configuration of forwarding elements within the context of the ForCES protocol, so that control elements (CEs) can control the FEs accordingly. More specifically, the model describes the logical functions that are present in an FE, what capabilities these functions support, and how these functions are or can be interconnected. This FE model is intended to satisfy the model requirements specified in RFC 3654. Status of This Memo This is an Internet Standards Track document.This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc5812.

BACKGROUND. We describe common surgical and medical hospital admission rates for Maryland residents, exploring systematic effects of race and income. METHODS. The data comprise Maryland hospital discharges and population estimates for 1985 to 1987. Patient income is the race-specific median family income of residence zip code. Logistic regression is used to measure incidence by race, income, and residence for surgical and medical reasons for admission. RESULTS. Population rates for discretionary orthopedic, vascular, and laryngologic surgery tend to increase with community income levels. Coronary and carotid artery surgery rates are two to three times higher among Whites. The more discretionary the procedure, the lower is the relative incidence among Blacks. By contrast, admission rates for most medical reasons decline with increasing income levels and are elevated among Blacks. The affluent receive coronary artery procedures whereas the poor are hospitalized for coronary artery disease. CONCLUSIONS. Blacks and the poor appear to have higher illness burdens requiring hospital care. Discretionary surgeries have a White predominance and increase with income; medical admissions have a Black predominance and decline with income. Race and community income level are important factors in differential hospital utilization rates.

Classical IP and ARP over ATM Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

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Network programmability has re-emerged as top item of the networking research agenda as Software Defined Networking (SDN) gained wide acceptance simultaneously in vendor product line plans and operator expectations for future deployments. One of the key ingredients for the successful deployment of SDN technologies are standardized models, mechanisms, and protocols for the separation of the control and forwarding planes. The Internet Engineering Task Force (IETF) standardization effort on Forwarding and Control Element Separation (ForCES) has published a set of standards track documents which specify in detail a comprehensive architectural framework and the respective standard protocols which can be employed to implement the separation of these two planes in a flexible, scalable and vendor-agnostic yet fully interoperable manner. The IETF standards on ForCES define how to achieve said separation through a complete and modular system model of the forwarding plane elements. In the ForCES model every network element is composed of numerous logically separate and well-defined functional entities that cooperate to provide the desired overall functionality, such as a routing or IP switching. The elegance of the model lies in the fact that a ForCES-based implementation of a network element is indistinguishable from a traditional ("closed-box") network element and therefore can be deployed in the field without any need for migration to a new architecture. Conversely, ForCES allows for rapid prototyping and agile deployment of new architectures as emphasis is placed on software-defined functionality and full programmability. The difference of ForCES from other SDN approaches that depend on logically centralized controllers and the deployment of solely simple or "dumb" switches is that ForCES standards provide a complete toolbox to design, implement, and interoperate ForCES-based network elements with both previously deployed infrastructures as well as in experimental or early-deployment phase endeavors. An example of the former is the implementation of 3GPP-standardized network elements such as a packet gateway (PGW). Examples of the latter include the use of ForCES for network function virtualization (NFV) proves-ofconcepts. This paper surveys the programmable networks and SDN area and provides a comprehensive tutorial on ForCES by summarizing numerous standards documents and thus making the technology easily understood by the wider research community. We present the design goals, choices and tradeoffs for this standardized approach for network programmability and provide a thorough primer on the ForCES model and protocol. The article also surveys recent independent interoperable implementations that showcase the full spectrum of ForCES applications in the era of NFV and SDN.

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