source

Source application

This application implements both source and sink for the experiments for the paper. It starts as an IPv6 router. There is also a dedicated sink application, but the only difference to this application is that the environment variable RB_SIZE defaults to 16.

Compile-time configuration

There are some compile-time configurations that are exposed to the via environment variables

• MODE: (default: hwr) Can be either hwr (for hop-wise reassembly), ff (for fragment forwarding), e2e (for end-to-end fragmentation), or sfr (for selective fragment recovery)
• CONJURE_IMPL: (optional) Sets the congestion control for sfr. Can either be congure_sfr (for congestion control as proposed in Appendix C of RFC 8931), congure_reno (for congestion control as proposed in RFC 5681), congure_abe (for congestion control as proposed in RFC 8511), or congure_quic (for congestion control as proposed in RFC 9002). If unset, sfr will be compiled without any congestion control and the window size will just be set to SFR_INIT_WIN_SIZE.
• APP_LOG: (default: 0 without CONGURE_IMPL, 1 with CONGURE_IMPL) Log congestion events.
• PKTBUF_SIZE: (default: 6144 without CONGURE_IMPL, 40960 with CONGURE_IMPL) Packet buffer size.
• NETIF_PKTQ_POOL_SIZE: (default: 64 without CONGURE_IMPL, 8 with CONGURE_IMPL) Network interface packet queue pool size
• FB_SIZE: (default: 64 without CONGURE_IMPL, 4 with CONGURE_IMPL) Fragmentation buffer size
• RB_SIZE: (default: 1) The size of the forwarder's reassembly buffer
• RB_TIMEOUT: (default: 10000000) Reassembly timeout in microseconds
• RB_DEL_TIMER: (default: 250) Deletion timer for reassembly buffer entry after datagram completion.
• VRB_SIZE: (default: 16) The size of the virtual reassembly buffer (with modes ff and sfr) reassembly buffer when full)
• SFR_INIT_WIN_SIZE: (default: 2) Window size for mode sfr. With CONGURE_IMPL set, this will be the initial window size used by the congestion control mechanism, with CONGURE_IMPL unset, this will be the window size throughout the whole experiment as well as the maximum window size (for allocation).
• SFR_INTER_FRAME_GAP: (default: 170000) Inter-frame gap in microseconds for mode sfr
• SFR_ARQ_TIMEOUT: (default: 2500) Retry timeout in milliseconds for mode sfr
• SFR_FRAG_RETRIES: (default: 4) Number of retries for mode sfr
• SFR_DATAGRAM_RETRIES: (default: 0) Number of datagram retries for mode sfr
• SFR_ECN_NUM: (default: 1) Numerator for ECN threshold fraction when CONGURE_IMPL is set.
• SFR_ECN_DEN: (default: 2) Denominator for ECN threshold fraction when CONGURE_IMPL is set.
• UDP_COUNT: (default: 200) Number of UDP packets the udp send command sends.

Usage

Once the node is up a global address can be configured using

ifconfig <if> add <addr>

The MTU for IPv6 can be changed (for e2e) using

ifconfig <if> set mtu <mtu>

The default route to upstream can be configured using

nib route <if> default <next-hop link-local addr>

To configure a 6LoWPAN compression context for global addresses use

6ctx add <context ID> <prefix> <ltime>

Once the experiment's network is set-up this way, the sending of periodic UDP packets can be started by using

udp send <sink global address>:<port> <payload length> <delay>

With <delay> being the mean in milliseconds of the randomized delay. The delay is uniquely distributed between 0.5×<delay> and 1.5×<delay>. <payload length> may not be 0 as the bytes of the payload are used to identify the packets at the sink.