Requirements for the backhaul QoS originate from the end user services, radio network layer operation, transport network control plane, synchronization and management plane. Backhaul service takes the above into account by supporting the treatment required for each of the traffic types. Instead of having a differentiated treatment for each service separately, traffic types are aggregated in the mobile backhaul, which simplifies the backhaul implementation.
In the radio network layer, scheduling occurs for an individual user bearer. In the backhaul, multiple users are aggregated and the aggregate is scheduled. Radio network and transport network QoS functions need to be aligned. In this way the user is served with the required quality and network resources in both the air interface and in the backhaul network are used efficiently.
All radio networks, 2G, 3G and LTE, have their own needs for the transport service. Each radio network technology specific channel or traffic type is taken into account and corresponding packet flow is marked accordingly. The starting point in marking is the Differentiated Services Code Point (DSCP) field of the IP packet header. The DSCP value is typically configurable, and deduced from the radio network layer channels and the bearer attributes, and configured for other traffic types, such as transport network control and packet based synchronization.
From DSCP, the mapping is carried over to other network layers such as MPLS or Ethernet (L2). Once the mapping to the DSCPs is performed, the backhaul network QoS is based on the DSCP value and on the corresponding Per-Hop-Behaviour/Treatment aggregate.
Notes
1. RED was originally introduced in order to prevent TCP synchronization. The RED together with the TCP Congestion control are the two dominant congestion control mechanism of the Internet. The scope of RED is to drop randomly selected packets (i.e., arriving packets are discarded with a certain probability that depends on the load of the buffer) in order to trigger TCP CC control actions and thus to reduce the load.
2. For this purpose, it is useful to consider some margin at the shaping function at the egress of the base station port. The shaping rate at the egress should be somewhat less than the defined CIR rate, in order not to lose traffic due to inaccuracies in the shaping/metering on either side of the UNI.
3. For planning purposes, monitoring of the actual bandwidth used per traffic class in the backhaul may reveal useful information. It clearly can be a trigger for modifying configuration of the weights. Often, it may as well indicate a shortage of capacity, which is addressed by expanding capacity in the backhaul network.
1. 3GPP TS22.105 Service aspects; Services and service capabilities, v10.0.0
2. IETF RFC 768 User Datagram Protocol (UDP)
3. IETF RFC 791 Internet Protocol (IP)
4. Jacobson, Karels: ‘Congestion Avoidance and Control’, Proceedings of the Sigcomm '88 Symposium, vol.18(4): pp. 314–329. Stanford, CA. August, 1988
5. IETF RFC 2581 TCP Congestion Control
6. IETF RFC 3782 The NewReno Modification to TCP's Fast Recovery Algorithm
7. Rhee: CUBIC for Fast Long-Distance Networks. Internet-Draft, 2008
8. IETF RFC 3168 The Addition of Explicit Congestion Notification (ECN) to IP, IETF, 2001
9. IETF RFC 1323 TCP Extensions for High Performance, IETF, 1992
10. Sridharan: Compound TCP: A New TCP Congestion Control for High-Speed and Long Distance Networks. Internet-Draft, 2008
11. Balakhrisnan, Seshan, Katz, ‘Improving Reliable Transport and Handoff Performance in Cellular Wireless Networks’, ACM Wireless Networks, vol.1, no. 4, Nov. 1995, pp. 469–481
12. Ratnam, Matta, ‘WTCP: An Efficient Mechanism for Improving TCP Performance overWireless Links,’ IEEE Symposium on Computers and Communications (ISCC), 1998.
13. Vangala, Labrador, ‘The TCP SACK-Aware-Snoop Protocol for TCP over Wireless Networks’, IEEE VTC, Orlando, FL, vol. 4, Oct. 2003
14. IETF RFC 2018 TCP Selective Acknowledgement Options.
15. Bakre, Badrinath: ‘I-TCP:Indirect TCP for Mobile Hosts’, Proc. IEEE ICDCS'95
16. Moller, Molero, Johansson, Petersson, Skog, Arvidsson, ‘Using Radio Network Feedback to Improve TCP Performance over Cellular Networks,’ Proc. of the 44th IEEE Conference on Decision and Control, December 2005.
17. Goff, Moronski, Phatak, Gupta, ‘Freeze-TCP: A true end-to-end TCP enhancement mechanism for mobile environments’, Proc. of IEEE Infocom 2000, Tel-Aviv, pp. 1537–1545, 26–30. Mar. 2000
18. Casetti, Gerla, Mascolo, Sanadidi, Wang, ‘TCP Westwood: end-to-end congestion control for wired/wireless networks’, Wireless Networks, v.8 n.5, p. 467–479, September 2002
19. IETF RFC 2474 Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers
20. IETF RFC 2475 An Architecture for Differentiated Services
21. IETF RFC 2597 Assured Forwarding PHB Group
22. IETF RFC 2598 An Expedited Forwarding PHB
23. IETF RFC 3246 An Expedited Forwarding PHB (Per-Hop Behavior)
24. IETF RFC 3260 New Terminology and Clarifications for Diffserv (Informational)
25. Wang: Internet QoS. Architectures and Mechanisms for Quality of Service. Morgan Kaufmann Publishers, 2001.
26. IETF RFC 5462 Multiprotocol Label Switching (MPLS) Label Stack Entry: ‘EXP’ Field Renamed to ‘Traffic Class’ Field
27. IETF RFC 3270 MPLS Support of Differentiated Services
28. IETF RFC 5865 A Differentiated Services Code Point (DSCP) for Capacity-Admitted Traffic
29. IETF RFC 4594 Configuration Guidelines for DiffServ Service Classes
30. IETF RFC 5127 Aggregation of DiffServ Service Classes
31. IETF RFC 1812 Requirements for IP Version 4 Routers
32. IEEE 802.1Q-2005 IEEE Standard for Local and metropolitan area networks, Virtual Bridged Local Area Networks
33. IETF RFC 2698 A Two Rate Three Color Marker
34. Soldani, Li, Cuny: QoS and QoE Management in UMTS Cellular Systems. Wiley, 2006.
35. 3GPP TS23.107 Quality of Service (QoS) concept and architecture, v10.1.0
36. 3GPP TS23.203 Policy and charging control architecture, v10.4.0, v10.4.0
37. 3GPP TS23.207 End-to-end Quality of Service (QoS) concept and architecture, v10.0.0
38. 3GPP TS 25.401 UTRAN overall description (Release 10), v10.2.0
39. 3GPP TR 25.902 Iub/Iur congestion control, v7.1.0
40. Kaaranen, Ahtiainen, Laitinen, Naghian, Niemi: UMTS Networks, Architecture, Mobility and Services, Second Edition, Wiley 2005
41. 3GPP TS 23.401 General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access, v10.5.0
42. 3GPP TS 36.300 Evolved Universal Terrestrial Radio Access (E-UTRA), Overall description, v10.5.0
43. 3GPP TS 36.401 Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Architecture description, v10.3.0
44. MEF 22 Mobile Backhaul Implementation Agreement – Phase 2, MEF, 2012
45. MEF 23 Carrier Ethernet Class of Service – Phase 2, MEF, 2012