Internet Draft S. Jobert Intended status: Informational I. Hamchaoui Expires: January 2014 W. Diego Orange July 11, 2013 Packet-oriented QoS management model for a wireless Access Point draft-jobert-iccrg-ip-aware-ap-00.txt Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. 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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 This Internet-Draft will expire on January 11, 2014. Jobert Expires January 11, 2014 [Page 1] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This document introduces a packet-oriented QoS management model applicable to a wireless Access Point, referred to as "IP aware Access Point". This model may be used in addition, or as a substitute to the connection-oriented traditional QoS model defined for cellular mobile networks, based on the notion of bearer. Table of Contents 1. Introduction ................................................. 2 2. Conventions used in this documen ............................. 4 3. Concepts and architecture .................................... 4 4. IP aware wireless Access Point behavior ...................... 6 5. Extension to upstream traffic ................................ 7 6. Examples of possible models .................................. 8 6.1. Model for intra-bearer arrangement ...................... 8 6.2. Models for inter-bearer arrangement ..................... 9 7. Security Considerations ...................................... 9 8. IANA Considerations .......................................... 9 9. References ................................................... 9 9.1. Normative References .................................... 9 9.2. Informative References ................................. 10 10. Acknowledgments ............................................ 10 1. Introduction The management of QoS in cellular mobile networks remains connection-oriented in many cases: when QoS differentiation is targeted, the general solution proposed by most existing cellular mobile standards consists in establishing several tunnels (e.g. bearers), one per class of service, between the mobile terminal (e.g. UE) and the wireless Access Point (e.g. NodeB, eNB). Jobert Expires January 11, 2014 [Page 2] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point The packets are then positioned into the various tunnels, depending on various criteria, for instance on the required QoS of the corresponding application. Adapted QoS treatments are then applied on the overall tunnels, according to the characteristics of the established bearers, but not at the packet level. In other words: even if an IP packet is marked (e.g. using DSCP marking) as being of high priority, this information inside the packet is not taken into account to schedule the packet over the radio interface, only the bearer that the packet belongs to matters. These tunnels are moreover in general extended up to an aggregation point in the network (e.g. GGSN, PDN-GW). Packet-oriented QoS management may however be applied over the fixed portion of the network, although tunnels are present. This connection-oriented model was inherited from TDM-based transport, and it was well adapted to early mobile data services deployments when the amount of data exchanged was low. It now raises important questions considering the high volumes and variability of mobile data traffic to be handled by most of mobile network operators generated by smartphones applications. In addition, managing the QoS of mobile networks using a connection- oriented model has clearly some drawbacks, such as: problems of scalability of the architecture due to the number of tunnels to be maintained simultaneously, additional signaling traffic required to establish or modify the parameters of the tunnels, time to establish or modify a tunnel, etc. In this draft, we introduce the concepts of a packet-oriented QoS management model applicable to a wireless Access Point, referred to as "IP aware Access Point", which can be considered as an alternative approach to the existing connection-oriented model. Note however that both models could be simultaneously deployed: a connection-oriented model could be used for managed ISP services when signaling traffic is exchanged prior to starting the service (a typical example might be managed VoLTE), while a packet-oriented model could be suitable to differentiate among the other services (e.g. Internet services), thanks to proper DSCP marking/remarking (according to the QoS policy enforced in the ISP-operated DiffServ domain). It is expected that this model be applicable to both licensed and unlicensed wireless networks (such as Wi-Fi). Jobert Expires January 11, 2014 [Page 3] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point 2. Conventions used in this document 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 [RFC2119]. In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying RFC-2119 significance. AP: Access Point CQI: Channel Quality Indicator DSCP: Differentiated Services Code Point eNB: evolved NodeB GGSN: Gateway GPRS Support Node Mifi: Mobile Wi-Fi NB: NodeB PDN-GW: Packet Data Network Gateway PF: Proportional Fair RB: Resource Block TTI: Transmission Time Interval UE: User Equipment VoLTE: Voice over LTE 3. Concepts and architecture Introducing a packet-oriented model in mobile networks is expected to simplify QoS management by leveraging the experience and current practice in fixed IP networks and permitting consistent operations over all network segments. Indeed, it simply reuses proven (and standard) mechanisms of fixed IP networks. It also solves most of the drawbacks of the connection-oriented approach. Finally, it Jobert Expires January 11, 2014 [Page 4] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point allows for global seamless offers over various wireline and wireless accesses. The proposed packet-oriented QoS management model consists in the following main principles (the description below applies mainly to the downstream direction, i.e. from the wireless AP to the terminal, but can be extended to the upstream direction, i.e. from the terminal to the wireless AP): o There is no need for establishing several tunnels to allow differentiated QoS treatments; multiple classes of service are defined for this purpose independently of the tunnels, allowing differentiated QoS treatments inside the same tunnel, which may be maintained for mobility purposes if needed. o The packets SHOULD be marked or re-marked properly at the ingress of the DiffServ domain corresponding to the mobile network, according to the applicable criteria (which may depend on the type of service, agreement between parties, etc.). The DSCP field in the header of the IP packets MUST be used for this purpose. This marking SHOULD be maintained transparently up to the IP aware Access Point. Depending on the applicable scenario, the DSCP marking function MAY be located in any upstream point from the IP aware access point, including the traffic source. o The IP aware wireless Access Point MUST classify the packets based on the marking indicated in each packet and differentiated treatments are applied on a packet-per-packet basis. The packets with the highest priority SHOULD for instance be positioned in a high priority queue, which is served first when radio resources are allocated to the terminal. Figure 1 below illustrates the proposed packet-oriented QoS management model, with an example where 3 classes have been configured in the IP aware Access Point (e.g. one for traffic requiring low delay/jitter, one for traffic requiring low packet loss, and one for Best Effort traffic). Note that the IP layer at the IP aware Access Point MAY NOT implement a full IP layer (e.g. only the DSCP marking in the IP header MUST be analyzed to classify the packets into the relevant queues, but the forwarding of the packets MAY be based on traditional relaying functions between the tunnel on fixed network and the radio layers). Jobert Expires January 11, 2014 [Page 5] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point +-----------------------------------------------------------------+ | ++ | #: Voice packet | | .----++ | +------------+ *: Video packet | | | .-. | Radio | +------+ | @: Email packet +-----+ | | | |#| |Scheduling| |#### | | #|Voice| | | | '-' | | | | +------+ | '-----' | | | .-. |==========| | Queue1 | # | | | |*| | +------+ | | +------+ |==================== +-----+ | | | '-' | |##*@ | | | |***** | |@ # * @ # * @ * # * *|Video| | | | .-. | +------+ | | +------+ |==================== @ '-----' | | | |@| |==========| | Queue2 | Fixed network | | | '-' | | | v +------+ | (backbone/backhaul) @ +-----+ | | '-----' | | |@@@ | | @|Email| | | Mobile | | +------+ | '-----' | | Terminal V | Queue3 | | | +------------+ | | +-------+ IP Aware Wireless AP +-------+ | | | App |---------------------------------------------| App | | | |-------| |-------| | | |TCP/UDP|---------------------------------------------|TCP/UDP| | | |-------| +-------+ +-------+ DSCP |-------| | | | IP |----------| IP |------| IP |--Marking--| IP | | | |-------| |-------| |-------| |-------| | | | L2 |----------| L2 |------| L2 |-----------| L2 | | | |-------| |-------| |-------| |-------| | | | L1 |----------| L1 |------| L1 |-----------| L1 | | | +-------+ +-------+ +-------+ +-------+ | | '---------v-----------' '------------------v------------------' | | Radio segment Wireline segment | +-----------------------------------------------------------------+ Figure 1 - Packet-oriented QoS management model in mobile networks 4. IP aware wireless Access Point behavior The IP aware Access Point MUST take into account the DSCP/ToS field of each packet prior to the transmission over the radio segment. For this purpose, an IP multiplexing stage (i.e. an IP queuing system) is added before the radio scheduler. This two-level scheduling process can be implemented through various algorithms. In some cases, it is relevant to consider a model which associates one set of IP queues to each terminal (see for instance the model in section 6.1). Jobert Expires January 11, 2014 [Page 6] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point In this draft, we distinguish two main types of behavior for the IP aware Access Point: o Intra-bearer arrangements: the allocation of radio resources is independent of the traffic mix waiting for transmission; in this case, radio resources allocated to a given user are determined by a basic radio scheduler which generally takes into account the radio conditions (e.g. algorithm based on Proportional Fairness). The addition of an IP priority queuing system per user before the radio scheduler (without influencing it) allows prioritizing the sensitive flows of a given user against his own other flows when populating the radio frame. o Inter-bearer arrangements: the allocation of the radio resources depends on the traffic mix waiting for transmission; in this case, the radio resources allocated to one UE not only depend on the radio conditions of the UE, but also on the traffic mix offered to the IP queuing system. This traffic mix is defined through the DSCP of its constitutive packets. Several approaches are possible (e.g. weighting the allocation according to the prioritized traffic volume / priority queue backlog, ensuring a maximum latency for certain classes, etc.) The first case (intra-bearer arrangement) is expected to be useful for multi-tasking users (e.g. user running several applications simultaneously, for instance in case of tethering terminals or acting as Mifi access point). This model is further detailed in section 6.1 of this document. The second case (inter-bearer arrangement) targets real time applications with stringent QoS constraints. This model is further detailed in section 6.2 of this document. 5. Extension to upstream traffic A future version of this draft will provide some details on the usage of the mechanism for upstream traffic. Note that some solutions, such as the model described in section 6.1 of this document, are already applicable to upstream traffic without changes in the mobile terminal. Jobert Expires January 11, 2014 [Page 7] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point 6. Examples of possible models The following sections provide examples of applicable models for intra-bearer and inter-bearer arrangements. It should be noted that these models are considered as examples only (mainly as references for simulation activity), and that actual implementations may differ from them. 6.1. Model for intra-bearer arrangement In this section, we describe the intra-bearer arrangement model. The aim of this model is to prioritize the sensitive flows of one UE against its own other flows without modifying the radio resources allocated to this UE. As a consequence, the good properties of the scheduling algorithm are preserved (e.g. trade-off between UE fairness and cell throughput), thus preserving the cell throughput capacity. As mentioned before, the "IP aware Access Point" MUST take into account the DSCP/ToS field, therefore an IP layer MUST be added on the eNB side, which is not the current practice in most existing cellular networks. In the present model, it is assumed that the marking procedure is performed upstream from the eNB. On the "IP aware Access Point" side, a two-level scheduler is implemented when considering an intra-bearer arrangement: The first level consists in an IP priority queuing system composed of "n" finite queues per UE (DiffServ model - one queue per level of QoS). These queues are operated according to a non-preemptive service policy. This means that if one or more high priority packets arrive when a packet of lower priority is served, the high priority packets will be served only after the current service of a low priority packet is complete. For the sake of simplicity, we propose the use of a strict priority policy between queues, but other policies are also possible, such as weighted fair queuing/weighted round robin. The service rate of this IP queuing system is constant during each TTI (Transmission Time Interval). It is calculated for each UE at each TTI by the second level described hereafter. The second level is a radio scheduler which shares the available radio resources (e.g. RB - Resources Block in LTE) between the UEs. Jobert Expires January 11, 2014 [Page 8] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point Different scheduling algorithms are possible for the allocation of radio resources depending on the optimization criteria (delay, throughput, etc., or trade-off between some of these criteria). On the present model, Proportional Fair (PF) scheduler, without any modification, is suggested because it offers a good trade-off between cell throughput and fairness between UEs, and because it is the basis of many scheduler implementations in base stations. PF assigns the available radio resources to UEs every TTI (Transmission Time Interval), regardless of the first level queuing process described above. The PF scheduler algorithm takes into account the radio conditions (e.g. CQI - Channel Quality Indicator in LTE) provided by each UE. 6.2. Models for inter-bearer arrangement A future version of this draft will provide some details on the applicable models for inter-bearer arrangements. 7. Security Considerations 8. IANA Considerations 9. References 9.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, Internet Mail Consortium and Demon Internet Ltd., November 1997. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Jobert Expires January 11, 2014 [Page 9] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point [RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, Internet Mail Consortium and Demon Internet Ltd., November 1997. 9.2. Informative References [3] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP and Its Effect on Busy Servers", Proc. Infocom 1999 pp. 1573- 1583. [4] Hamchaoui, I., Jobert, S., Boufelja, S., "IP aware radio scheduling - Introducing IP QoS management in LTE networks", IEEE ICC'13, June 2013 10. Acknowledgments This document was prepared using 2-Word-v2.0.template.dot. Jobert Expires January 11, 2014 [Page 10] Internet-Draft Packet-oriented QoS management model July 2013 for a wireless Access Point Authors' Addresses Sébastien Jobert Orange 2 avenue Pierre Marzin 22300 LANNION, FRANCE Email: sebastien.jobert@orange.com Isabelle Hamchaoui Orange 2 avenue Pierre Marzin 22300 LANNION, FRANCE Email: isabelle.hamchaoui@orange.com William Diego Orange 2 avenue Pierre Marzin 22300 LANNION, FRANCE Email: william.diego@orange.com Jobert Expires January 11, 2014 [Page 11]