[Serusers] SER PSTN Failover

Hello All, I am having a problem with the t_on_failure failure route using SER. I have been using SER for 2+ years now and am servicing 5000+ voip customers but now we are moving to a PSTN termination partner who does not have redundant gateways. So I would like to setup SER so that I have call route advance to a 2nd PSTN carrier if the 1st fails. However, I am running into some snags... With my configuration the call is processed correctly if the 1st PSTN carrier takes the call. However, when the failover happens then I get some odd behavior. The call is initially setup correctly with the failover carrier, but then it hangs up after about 5-7 seconds and a new call comes in to the called number, and a loop begins where this same call keeps coming in one after another until SER is restarted. I do get the following errors on the SER console. 0(17304) forward_req: ERROR: cannot forward to af 2, proto 2 no corresponding listening socket 0(17304) Warning: sl_send_reply: I won't send a reply for ACK!! 0(17304) ERROR: sl_reply_error used: I'm terribly sorry, server error occurred (7/SL) It almost seems as if the the 1st route PSTN carrier is not accepting my ACK when I send it in response to the 403 Forbidden that they send to me. Then they just keep sending the 403 Forbidden over and over again. Each time that they do that then SER processes it as a failed call and starts a new call to the secondary PSTN carrier. Does this sound possible? Or am I way off base here? I have attached my basic lab test SER cfg that I have been using to test with. Perhaps someone can tell me what I might be doing incorrectly? Or - Is there a better way to do this? ie. With AVP-Pops? If so, does anyone have a sample configuration that I can look at? Thanks so much for any help provided!! Darren Nay Ionosphere, Inc. dnay(a)ionosphere.net +1 864-678-3158 # ----------- global configuration parameters ------------------------ debug=3 # debug level (cmd line: -dddddddddd) fork=yes log_stderror=no # (cmd line: -E) memlog=0 #uncomment for debug mode debug=3 fork=no log_stderror=yes #Bind IP listen=XX.XX.XX.XX check_via=no # (cmd. line: -v) dns=yes # (cmd. line: -r) rev_dns=no # (cmd. line: -R) port=5060 children=5 mhomed=no # multi-homed? fifo="/tmp/ser_fifo" # ------------------ module loading ---------------------------------- loadmodule "/usr/local/lib/ser/modules/nathelper.so" loadmodule "/usr/local/lib/ser/modules/textops.so" loadmodule "/usr/local/lib/ser/modules/sl.so" loadmodule "/usr/local/lib/ser/modules/tm.so" loadmodule "/usr/local/lib/ser/modules/rr.so" loadmodule "/usr/local/lib/ser/modules/maxfwd.so" loadmodule "/usr/local/lib/ser/modules/usrloc.so" loadmodule "/usr/local/lib/ser/modules/registrar.so" loadmodule "/usr/local/lib/ser/modules/xlog.so" # ----------------- setting module-specific parameters --------------- # -- timers -- modparam("tm", "wt_timer", 10) modparam("tm", "retr_timer1p1", 2) # -- usrloc params -- modparam("usrloc", "db_mode", 0) # -- rr params -- modparam("rr", "enable_full_lr", 1) # -- Nathelper -- modparam("registrar", "nat_flag", 6) modparam("nathelper", "natping_interval", 10) modparam("nathelper", "ping_nated_only", 1) modparam("nathelper", "rtpproxy_disable", 1) alias=proxy.ionosphere.net # ------------------------- request routing logic ------------------- # main routing logic route { # initial sanity checks -- messages with # max_forwards==0, or excessively long requests if (!mf_process_maxfwd_header("10")) { sl_send_reply("483","Too Many Hops"); break; }; if (msg:len > max_len) { sl_send_reply("513", "Message too big"); break; }; # Nathelper if (method == "REGISTER" || !search("^Record-Route:.*XX.XX.XX.XX")) { fix_nated_contact(); # Rewrite contact with source IP of signaling force_rport(); setflag(6); }; # we record-route all messages -- to make sure that # subsequent messages will go through our proxy; that's # particularly good if upstream and downstream entities # use different transport protocol if (!method=="REGISTER") record_route(); # loose-route processing if (loose_route()) { route(1); break; }; lookup("aliases"); if (!uri==myself) { route(1); break; }; # if the request is for other domain use UsrLoc # (in case, it does not work, use the following command # with proper names and addresses in it) if (uri==myself) { if (method=="REGISTER") { fix_nated_register(); save("location"); break; }; }; ### Process URI routing # Now we determine if called number is on # or off net and route accordingly if (!lookup("location")) { route(2); # Nothing found - Route Off-Net } else { route(1); # Direct match - Route On-Net }; } # # No direct route via location or location_novm (Off-Net Route) # route[2] { t_on_failure("2"); #Send the call to Level3 rewritehostport("XX.XX.XX.XX:5060"); if (!t_relay()) { sl_reply_error(); }; break; } # # Direct route found via location or location_novm (On-Net Route) # route[1] { # !! Nathelper if (uri=~"[@:](192\.168\.|10\.|172\.(1[6-9]|2[0-9]|3[0-1])\.)" && !search("^Route:")) { sl_send_reply("479", "We don't forward to private IP addresses"); break; }; # if client or server know to be behind a NAT, enable relay if (isflagset(6)) { # NAT processing of replies; apply to all transactions (for example, # re-INVITEs from public to private UA are hard to identify as # NATed at the moment of request processing); look at replies t_on_reply("1"); append_hf("P-Behind-NAT: Yes\r\n"); }; # send it out now; use stateful forwarding as it works reliably # even for UDP2TCP if (!t_relay()) { sl_reply_error(); }; } onreply_route[1] { if (status =~ "(183)|(180)|2[0-9][0-9]") { fix_nated_contact(); }; if (nat_uac_test("1")) { fix_nated_contact(); }; break; } failure_route[2] { # forwarding failed try again at another destination rewritehostport("XX.XX.XX.XX:5060"); append_branch(); t_relay(); break; }