Udpcast August 2023

udpcast@udpcast.linux.lu

2 discussions

Clarifying --fec argument
by Peter Story 01 Oct '23

01 Oct '23

Hello, I am running some benchmarks using UDPcast for a paper, and I wanted to confirm that I’ve understood the --fec argument. Here is what I’ve written: > The --fec argument specifies how many “stripes” each chunk of data is split into, the number of FEC packets included with each stripe, and the number of data packets in each stripe. For example, with --fec 8x16/128 each chunk of data will be sent in 8 stripes, and each stripe will have 16 FEC packets and 128 data packets. Hoping someone can confirm I’ve understood things correctly, or can correct me. Thanks! -Peter

2 1

ttl multicast problem
by julien soula 01 Oct '23

01 Oct '23

hello, we found a problem in using updcast in a context of multi-routers when the rdv-addr is not multicast. Indeed, in this case, the multicast ttl must be greater than 1 (--ttl). But it is only assign during the processing of rdv-addr and only if rdv-addr is a multicast IP : udps-negotiate.c: /* Only do the following if controlMcastAddr is indeed an mcast address ... */ if(isMcastAddress(&net_config->controlMcastAddr)) { setMcastDestination(sock[0], net_config->net_if, &net_config->controlMcastAddr); setTtl(sock[0], net_config->ttl); But it is not assign during the processing of data-addr : udps-negotiate.c: if(isMcastAddress(&net_config->dataMcastAddr)) setMcastDestination(sock, net_config->net_if, &net_config->dataMcastAddr); Therefore, if rdv-addr is unicast then TTL remains to 1. So I suggest to patch the code this way : - if(isMcastAddress(&net_config->dataMcastAddr)) + if(isMcastAddress(&net_config->dataMcastAddr)) { setMcastDestination(sock, net_config->net_if, &net_config->dataMcastAddr); + setTtl(sock, net_config->ttl); + } Best regards, -- Julien Soula, Ingenieur Reseau, DSI/ULR2694, Universite de Lille, tel (0)3 20 62 34 55

2 1

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Udpcast August 2023