Communications Resource Priority for the Session Initiation Protocol (SIP)

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress". Abstract This document defines two new SIP header fields for communications resource priority, namely "Resource-Priority" and "Accept-Resource-Priority". The Resource-Priority header field can influence the behavior of SIP UAs, such as GSTN gateways, and SIP proxies. It does not directly influence the forwarding behavior of IP routers. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [1]. 2 Introduction During emergencies, communications resources including telephone circuits, IP bandwidth and gateways between the circuit-switched and IP networks may become congested. Congestion can occur due to heavy usage, loss of resources caused by the natural or man-made disaster and attacks on the network during man-made emergencies. This congestion may make it difficult for persons charged with emergency assistance, recovery or law enforcement to coordinate their efforts. As IP networks become part of converged or hybrid networks along with public and private circuit-switched (telephone) networks, it becomes necessary to ensure that these networks can assist during such emergencies. Also, users may want to interrupt their lower-priority communications activities and dedicate their end system resources to the high-priority communications attempt if a high-priority communications request arrives at their end system. There are many IP-based services that can assist during emergencies. This memo only covers requirements for real-time communications applications involving SIP, including voice-over-IP, multimedia conferencing and instant messaging/presence. Session Initiation Protocol (SIP) [2] applications involve at least five different resources that may become scarce and congested during emergencies. These resources include gateway resources, circuit-switched network resources, IP network resources, receiving end system resources and SIP proxy resources. IP network resources are beyond the scope of SIP signaling and are therefore not considered here. In order to improve emergency response, it may become necessary to prioritize access to SIP-signaled resources during periods of emergency-induced resource scarcity. We call this "resource prioritization". Currently, SIP does not include a mechanism that allows a request originator to indicate …