INTERNET-DRAFT draft-oh-avt-rtcp-qos-signaling-00.txt Sejong Oh/SAMSUNG AIT 14 June 2004 Expires December 2004 QoS renegotiation using RTCP inband signaling Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 6 of RFC 1889. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. "Copyright (C) The Internet Society (date). All Rights Reserved. Abstract The control protocol, RTCP, provides for periodic reporting of reception quality, participant identification and other source description information, notification on changes in session membership, and the information needed to synchronize media streams. This document defines and extends these RTCP functionalities to provide with the end-to-end QoS renegotiation using fast in-band signaling during the active session states. The main purpose of this new function of RTCP is to support the handover between heterogeneous access networks with different QoS factors such as available bandwidth etc. Sejong Oh. Expires December 2004 [Page 1] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004 Table of Contents 1 Introduction.................................................3 1.1 Definitions.............................................3 1.2 Terminology.............................................5 2 QoS issues in seamless VHO...................................5 2.1 Handover decision.......................................5 2.2 Radio Resource Management...............................6 2.2.1 Handover Management...............................6 2.2.2 Call Admission Control............................6 2.3 Routing path update.....................................6 3 QoS renegotiation after handover.............................7 3.1 Basic assumption in seamless VHO........................7 3.2 The role of RTCP in immediate feedback mode ............7 3.3 The role of Crossover router............................8 3.4 Procedure...............................................8 4 Format of RTCP Feedback Message for QoS renegotiation........9 5 Security Considerations.....................................10 6 Authors' Addresses..........................................10 7 IPR Notice..................................................10 7 References..................................................10 Sejong Oh. Expires December 2004 [Page 2] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004 1 Introduction As we move toward next-generation all-IP wireless networks, we are facing the integration of heterogeneous networks, such as WWAN and WLAN, where the vertical handover (VHO : Handover between heterogeneous access networks) is required. In vertical handover, mobile hosts should be able to move freely across different networks while satisfying QoS requirements for a variety of applications. Considering these day's applications require accurate synchronization and fast interaction, it is very natural to use RTP and RTCP as its transport layer. In order to provide consistent QoS control over an integrated heterogeneous access network, end-to-end QoS renegotiation procedure using RTCP feedback capacity is proposed in this document. The control protocol, RTCP, provides for periodic reporting of reception quality, participant identification and other source description information, notification on changes in session membership, and the information needed to synchronize media streams. This document defines and extends these RTCP functionalities to provide with the end-to-end QoS renegotiation using fast in-band signaling during the active session states. The main purpose of this new function of RTCP is to support the seamless VHO with different QoS factors such as available bandwidth etc. 1.1 Definitions The definitions from RTP/RTCP [1] and the RTCP feedback [2] apply. In addition, the following definitions are used in this document: Candidate access network : An access network to which a mobile node requests to move from the previous access network. Correspondent node : An RTP entity that transmits media packets as well as RTCP packets and receives Regular as well as QoS renegotiation request packet. This node must be able to modify active active session features such as transmisssion rate and flow specification etc. so as to handle the QoS renegotiation request from the mobile node. Sejong Oh. Expires December 2004 [Page 3] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004 Crossover Router : A router that manages the layer 2 tunnels of previous access network and candidate access network. The old and new layer 2 tunnels can be divided and merged here. In 3GPP specification, crossover router can be Packet Data Gateway (PDG) which should be the SGSN or GGSN depending on the inter-network architecture. There should be some additional functionalites to monitor the handover request and switch the layer 2 tunnels so as not to lose any packets during handover. Horizontal Handover : Handover in homogeneous access networks. L2 trigger event : An observation made by the layer 2 of mobile node which is (potentially) of interest to the sender -- such as a handover triggering or request of service level change, etc. -- and thus useful to be reported back to the sender by means of a Feedback message. This feedback message can be delivered as the early RTCP packet [2] in early RTCP mode [2]. Layer 2 tunnel : used for integrating multi-protocol dial-up services into existing Internet Service Providers Point of Presence. PPP defines an encapsulation mechanism for transporting multiprotocol packets across layer 2 (L2) point-to-point links. Typically, a user obtains a L2 connection to a Network Access Server (NAS) using one of a number of techniques (e.g., dialup POTS, ISDN,ADSL, etc.) and then runs PPP over that connection. Mobile node : An RTP entity that receives media packets as well as RTCP packets and transmits Regular as well as QoS renegotiation request packet. This node must detect the handover event and decide whether it can do handover negotiating with the radio resource management functions in each access network. And as it decides to do handover, it should initiates the radio channel setup to candidate access network and QoS renegotiation with Correspondent node. Previous access network : An access network from which a mobile node requests to move to the candidate access network because the signal strength of it decreases to the level with which a mobile node cannot recognize the bit information any more. Sejong Oh. Expires December 2004 [Page 4] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004 QoS renegotiation message : One kind of RTCP feedback message [2] newly defined in this document is used to convey information about events observed at a mobile node -- in addition to long-term receiver status information which is carried in RTCP RRs -- back to the sender of the media stream (Correspondent Node). Vertical Handover (VHO) : Handover between heterogeneous access networks such as WWAN and WLAN. 1.2 Terminology 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 [5]. 2 QoS issues in seamless VHO 2.1 Handover decision Not like the handover in homogeneous wireless systems (horizontal handover), following challenges exist in VHO. o When a user moves from WWAN to WLAN, since the WWAN is usually always on, the handoff cannot be triggered by signal decay of the current system, as in horizontal handoff. o In vertical handoff between WWAN and WLAN, there is no comparable signal strength available to aid the decision as in horizontal handoff o During a handoff procedure, the metrics upper-layer applications are really interested in are network conditions (available band- width and delay, user preference, etc), rather than the physical layer parameters such as received signal strength and signal-to- interference ratio. Sejong Oh. Expires December 2004 [Page 5] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004 2.2 Radio Resource Management Users are going to be requesting different services with different QoS parameters and values. In this context, Radio Resource Management (RRM) strategies or functions will be fundamental in providing the QoS required, which means focusing on handover management and call admission control are the issues of RRM. 2.2.1 Handover Management In general, this kind of RRM is to support for terminal mobility wherever the mobile node changes its point of attachment to the network. Each handover means network resources have to route the call to the next base station. If handover does not occur quickly, the QoS may degrade to below an acceptable level and the connection will be dropped. 2.2.2 Call Admission Control Call Admission Control (CAC) is a provisioning strategy used to limit the number of call connections into the networks in order to reduce the network congestion and provide the desired QoS to already established connections. The function of CAC is to make the decision of whether to accept or reject a new connection request (call) with certain traffic characteristics and associated QoS parameters. 2.3 Routing path update This issue is closely related with the interworking network architecture which has been supposed to be tightly or loosely. Each way of network integration has its own characteristic features like below Tightly integrated : o It makes one network appear as another, e.g., makes a WLAN network appear as another WWAN network. o Each network emulates the function of the other, i.e., a WLAN network injects traffic into WWAN network using WWAN networking protocols. o Typically, the same operator shares the different types of networks, i.e., same operator owns the WWAN as well as WLAN networks. o Possible to allow different operators also. Sejong Oh. Expires December 2004 [Page 6] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004 Loosely coupled : o It is kind of master slave architecture, e.g., WWAN could be the master and WLAN, the slave. o Combined emulator for several networks, e.g. a WLAN ESS connected to a combined WWAN Gateway emulator. o Each network uses different IP addresses in different domains. o It requires different handling of signaling and data traffic. Signaling goes to the wireless network and data goes directly to the IP network In terms of routing path update, the tightly integrated network arch- tecture is much more efficient because it needs no change in IP address and can have fast handover with less packet loss. 3. QoS renegotiation after handover It is generally considered that radio resource which can be proposed as available radio bandwidth is the most important QoS factor in VHO, and the different available bandwidth between heterogeneous access network, e.g. WWAN and WLAN, is therefore the most big problem we have to get over. This section shows the role of Mobile node, Correspondent node and crossover router and how these nodes can interact to handle this bandwidth problem in VHO procedure. 3.1 Basic assumption in seamless VHO Not like the horizontal handover, VHO has some special features like below o Dual connectivity over wireless : In general, VHO possible mobile node is equipped with more than two kind of network interface card, e.g. CDMA modem for WWAN, LAN card for WLAN, which can provide with more than two different wireless connectivity during handover. This can be supported with Multi- homing scheme discussed in other working groups. Based on this features of VHO, we can assume that if we properly design the hand- over schemes and network architecture, it is possible to have no packet delay or loss during VHO. 3.2 The role of RTCP in Immediate Feedback Mode Regular RTCP mode is based on periodical way to report reception quality, participant identification and other source description information, notification on changes in session membership, and the information needed to synchronize media streams. But this mode cannot support the event-driven signaling for handover and QoS renegotiation. By using Immediate Feedback Mode [2], the mobile node can directly report its handover event and QoS renegotiation request caused by radio resource allocation procedure. Sejong Oh. Expires December 2004 [Page 7] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004 3.3 The role of Crossover router Crossover router can manage the states of the RTP flows to remove the packet loss or delay during the VHO caused by the narrower bandwidth which the candidate access network can provide with. States which the crossover router can manage are "Active" and "VHO_pending". "Active" is the usual state in which every RTP packet go through crossover router without any checking inside. As mobile node starts VHO and is notified that less resource than requested can be available in the candidate network, it must send this situation to crossover router as well as to correspondent node. Right after the crossover router receives information from the mobile node, its state transits to "VHO_pending". "VHO_pending" is the newly designed state in which the router can look into the 'M' bit of RTP common header just to see the RTP sender (correspondent node) change its QoS level as requested by the mobile node. The crossover router in "VHO_pending" will prepare the new layer 2 tunnel through candidate access network but still transmits the packets through the old layer 2 tunnel. As The crossover router in "VHO_pending" can look into the "M' bit of RTP packet, The RTP sender can notify its execution of modifying QoS level to the crossover router by setting the "M" bit. Right after the crossover router finds the "M" set, it transits from "VHO_pending to "Active" again. +----------+ +-------------+ +----------+ | Active | <---> | VHO_pending | <---> | Active | +----------+ +-------------+ +----------+ 3.4 Procedure As the medium access control (MAC)-layer of mobile node senses and delivers the handover related information to the upper layer, the radio resource module of mobile node asks to get the required radio resource from the candidate access network. If the candidate access network can support the required amount of radio resource for the mobile node, it simply set up the new layer 2 tunnel from the cross- over router to the mobile node through the candidate access network and switch it with old layer 2 tunnel which cover from the crossover router to the mobile node through the previous access network. If the candidate access network cannot support the required amount of radio resource for the mobile node, it notify this to the mobile node with the current available amount of radio resources. Then the mobile node has to have two kind of signaling with crossover router and correspondent node respectively. The correspondent node should be the RTP sender as well. Sejong Oh. Expires December 2004 [Page 8] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004 Getting the signal message for VHO with minimum possible radio res- ource, the crossover router set up the new layer 2 tunnel. Instead of switching to new layer 2 tunnel immediately, the crossover router changes the session state from "Active " to "VHO_pending". The correspondent node which should be notified with QoS renegotiation from the mobile node will set the 'M' bit of RTP right after it finishes the modification of the QoS level of that flow. Getting the RTP packet with 'M' bit set from the correspondent node, the crossover router will immediately change its state from "VHO_pending" to "Active" and switch the old layer 2 tunnel with the new layer 2 tunnel. This layer 2 tunnel switching procedure executed by crossover router can remove the packet loss caused by the narrower bandwidth which the candidate access network can provide with. RTP receiver RTP sender (mobile node) Crossover Router (Correspondent node) ---------------------------------------------- | VHO_request | | | (less res.) | | |->->->->->->->->->->| (VHO_pending) | | | | QoS_Renegotiation | | (available level) | |->->->->->->->->->->->->->->->->->->->->+| | | | | | RTP packet | | | with 'M' bit set | | (Active) |<-<-<-<-<-<-<-<-<-<-| |<-<-<-<-<-<-<-<-<-<-| | | | | 4 Format of RTCP Feedback Message for QoS renegotiation This section defines the format of the Application layer message [2] which can be used as QoS renegotiation request during VHO. This message is used to transport VHO support module defined data directly from the receiver's to the sender's application. Therefore, the application MUST be able to identify the messages payload. Usually, VHO support module defines its own set of messages, This messages do not need any additional information from the RTCP message. Thus the application message is simply placed into the Feedback Control Information (FCI) field [2] as follows and the length field is set accordingly. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |V=2|P| FMT | PT | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of packet sender | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of media source | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Feedback Control Information (FCI) : : : Figure 1: Packet Format for QoS renegotiation Message Sejong Oh. Expires December 2004 [Page 9] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004 5 Security Considerations This QoS renegotiation signaling using RTCP FB message is designed based on end-to-end scheme to prevent from the various kind of attacks. Hence, this profile does not specify any additional security services. This profile modifies the timing behavior of RTCP and eliminates the minimum RTCP interval of five seconds and allows for earlier feedback to be provided by receivers. Group members of the associated RTP session (possibly pretending to represent a large number of entities) may disturb the operation of RTCP by sending large numbers of RTCP packets thereby reducing the RTCP bandwidth available for Regular RTCP reporting as well as for Early FB messages. All of these problems can be solved by the methods mentioned in [2] 6 Authors' Address Sejong Oh sejong.oh@samsung.com Mt. 14-1, Nongseo-Ri, Giheung-Eup, Yongin-si, Gyeonggi-Do, 449-712, Korea Tel. +82-31-280-9552 Fax. +82-31-280-5796 7 IPR Notice By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, or will be disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668." 8 References [1] H. Schulzrinne, S. Casner, R. Frederick, V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications," RFC 1889, January 1996. [2] Joerg Ott, Stephan Wenger, Noriyuki Sato, Carsten Burmeister, Jose Rey, "draft-ietf-avt-rtcp- feedback-08.txt", 31 January 2004, Expires July 2004 Sejong Oh. Expires December 2004 [Page 10] Internet Draft draft-oh-avt-rtcp-qos-signaling-00.txt 14 June 2004