TCP and Network Coding: Equilibrium and Dynamic Properties

Hamlet Medina Ruiz (1, 2) , Michel Kieffer (1, 2) , Beatrice Pesquet-Popescu (3)

1 L2S - Laboratoire des signaux et systèmes
2 LTCI - Laboratoire Traitement et Communication de l'Information
3 LTCI - Laboratoire Traitement et Communication de l'Information

This paper analyzes the impact on the stability of the TCP-Reno congestion control mechanism when a network coding (NC) layer is inserted in the TCP/IP stack. A model of the dynamics of the TCP-NC protocol combined with random early detection (RED) as active queue management mechanism is considered to study the network equilibrium and stability properties. The existence and uniqueness of an equilibrium point is demonstrated and characterized in terms of average throughput, loss rate, and queue length. Global stability is proved in absence of forward delay, and the effects of the NC redundancy factor and of the delay on the local stability of TCP-NC-RED are studied around the equilibrium. The fairness of TCP-NC with respect to TCP-Reno-like protocols is also studied. A version of TCP-NC with adaptive redundancy factor (TCP-NCAR) is also introduced. Results provided by the proposed model are compared with those obtained by simulation for N sources sharing a single link. TCP-NC-RED becomes unstable when delay or capacity increases, as TCP-Reno does, but also when the redundancy factor increases. Its stability region is characterized as a function of the redundancy factor. If TCP-NC and TCP-Reno share the same links, TCP-NC is fair with TCP-Reno-like protocols when no redundancy is added. Simulations show that TCP-NCAR is able to compensate losses on the wireless parts of the network.

Mots clés: queueing analysis; network coding; stability analysis; Index Terms-congestion control

Domaines: Traitement du signal et de l'image [eess.SP]

Hamlet Medina Ruiz, Michel Kieffer, Beatrice Pesquet-Popescu. TCP and Network Coding: Equilibrium and Dynamic Properties. IEEE/ACM Transactions on Networking, 2016, 24 (4), pp.1935-1947. ⟨10.1109/TNET.2015.2477349⟩. ⟨hal-01260537⟩