We investigate packet discarding schemes for transport control protocol (TCP) over asynchronous transfer mode with guaranteed frame rate service. In this letter, we propose the selective weighted fair allocation (SWFA) scheme, which discards packets from selected sessions. 15 TCP connections with equal minimum cell rate (MCR) and unequal MCRs are simulated. The SWFA scheme with per-virtual connection (VC) queuing is compared with early packet discard (EPD) with first-in, first-out queuing, EPD with per-VC queuing, and differential fair buffer allocation with per-VC queuing. Our results show that SWFA with per-VC queuing achieves significant enhancement on throughputs, goodputs, and fairness.

UBR connections of ATM networks provide no service guarantees. Schemes such as EPD (early packet discard) or PPD (partial packet discard), though improving the goodputs of packets over UBR (unspecified bit rate), cannot guarantee a MCR (minimum cell rate) for each flow. Guerin and Heinanen (1996) proposed a new service, which was originally called "UBR+" and is now called GFR (guaranteed frame rate), to assure a MCR for each flow. We investigate packet-discarding schemes for TCP over ATM with GFR service. We propose the SWFA (selective weighted fair allocation) scheme, which discards packets from selected sessions. 15 TCP connections with equal MCR and unequal MCRs are simulated. The SWFA scheme with per-VC queuing is compared with EPD with FIFO queuing, EPD with per-VC queuing and DFBA (differential fair buffer allocation) with per-VC queuing. Our results show that SWFA with per-VC queuing achieves significant enhancement on throughputs, goodputs, and fairness.