Effectivement le recueil est plus lisible.
Où puis-je trouver un tutoriel sur ngrep?

Code:
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U 2014/02/06 22:37:32.261729 192.168.1.17:5060 -> 91.121.129.20:5060
  OPTIONS sip:sip.ovh.fr SIP/2.0..Via: SIP/2.0/UDP 89.83.76.95:5060;branch=z9hG4bK4837ecdd;rport..Max-Forwards: 70..From: "asterisk" <sip:00
  33184230751@89.83.76.95>;tag=as018a36ad..To: <sip:sip.ovh.fr>..Contact: <sip:0033184230751@89.83.76.95:5060>..Call-ID: 0bd2a2ce4b2824e33cf
  ee1b022d45659@89.83.76.95:5060..CSeq: 102 OPTIONS..User-Agent: Asterisk PBX 10.7.0..Date: Thu, 06 Feb 2014 21:37:32 GMT..Allow: INVITE, AC
  K, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH..Supported: replaces, timer..Content-Length: 0....                       
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U 2014/02/06 22:37:32.270200 192.168.1.17:5060 -> 91.121.129.20:5060
  OPTIONS sip:sip.ovh.fr SIP/2.0..Via: SIP/2.0/UDP 89.83.76.95:5060;branch=z9hG4bK4806d636;rport..Max-Forwards: 70..From: "asterisk" <sip:00
  33183626986@89.83.76.95>;tag=as634bdb0c..To: <sip:sip.ovh.fr>..Contact: <sip:0033183626986@89.83.76.95:5060>..Call-ID: 7b4cd238708d7ef01ae
  706a968dfa1d5@89.83.76.95:5060..CSeq: 102 OPTIONS..User-Agent: Asterisk PBX 10.7.0..Date: Thu, 06 Feb 2014 21:37:32 GMT..Allow: INVITE, AC
  K, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH..Supported: replaces, timer..Content-Length: 0....                       
#
U 2014/02/06 22:37:32.304402 91.121.129.20:5060 -> 192.168.1.17:5060
  SIP/2.0 501 Not Implemented..Call-ID: 0bd2a2ce4b2824e33cfee1b022d45659@89.83.76.95:5060..CSeq: 102 OPTIONS..From: "asterisk" <sip:00331842
  30751@89.83.76.95>;tag=as018a36ad..To: <sip:sip.ovh.fr>;tag=00-24427-11ecb20a-315ffcd57..Via: SIP/2.0/UDP 192.168.1.17:5060;received=89.83
  .76.95;rport=5060;branch=z9hG4bK4837ecdd..Content-Length: 0....                                                                           
#
U 2014/02/06 22:37:32.314332 91.121.129.20:5060 -> 192.168.1.17:5060
  SIP/2.0 501 Not Implemented..Call-ID: 7b4cd238708d7ef01ae706a968dfa1d5@89.83.76.95:5060..CSeq: 102 OPTIONS..From: "asterisk" <sip:00331836
  26986@89.83.76.95>;tag=as634bdb0c..To: <sip:sip.ovh.fr>;tag=00-26343-11ecb20e-1ac4a0e27..Via: SIP/2.0/UDP 192.168.1.17:5060;received=89.83
  .76.95;rport=5060;branch=z9hG4bK4806d636..Content-Length: 0....                                                                           
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U 2014/02/06 22:37:42.896864 192.168.1.6:11340 -> 192.168.1.17:5060
  INVITE sip:0148734812@192.168.1.17 SIP/2.0..Via: SIP/2.0/UDP 192.168.1.6:11340;branch=z9hG4bK822768107;rport..From: "400" <sip:400@192.168
  .1.17>;tag=1168804521..To: <sip:0148734812@192.168.1.17>..Call-ID: 1392563310-11340-5@BJC.BGI.B.G..CSeq: 40 INVITE..Contact: "400" <sip:40
  0@192.168.1.6:11340>..X-Grandstream-PBX: true..Max-Forwards: 70..User-Agent: Grandstream GXP2140 1.0.0.17..Privacy: none..P-Preferred-Iden
  tity: "400" <sip:400@192.168.1.17>..Supported: replaces, path, timer..Allow: INVITE, ACK, OPTIONS, CANCEL, BYE, SUBSCRIBE, NOTIFY, INFO, R
  EFER, UPDATE, MESSAGE..Content-Type: application/sdp..Accept: application/sdp, application/dtmf-relay..Content-Length:   375....v=0..o=400
   8002 8000 IN IP4 192.168.1.6..s=SIP Call..c=IN IP4 192.168.1.6..t=0 0..m=audio 5012 RTP/AVP 0 8 18 9 97 2 101..a=sendrecv..a=rtpmap:0 PCM
  U/8000..a=ptime:20..a=rtpmap:8 PCMA/8000..a=rtpmap:18 G729/8000..a=fmtp:18 annexb=no..a=rtpmap:9 G722/8000..a=rtpmap:97 iLBC/8000..a=fmtp:
  97 mode=30..a=rtpmap:2 G726-32/8000..a=rtpmap:101 telephone-event/8000..a=fmtp:101 0-15..                                                 
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U 2014/02/06 22:37:42.897726 192.168.1.17:5060 -> 192.168.1.6:11340
  SIP/2.0 100 Trying..Via: SIP/2.0/UDP 192.168.1.6:11340;branch=z9hG4bK822768107;received=192.168.1.6;rport=11340..From: "400" <sip:400@192.
  168.1.17>;tag=1168804521..To: <sip:0148734812@192.168.1.17>..Call-ID: 1392563310-11340-5@BJC.BGI.B.G..CSeq: 40 INVITE..Server: Asterisk PB
  X 10.7.0..Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH..Supported: replaces, timer..Contact: <sip:014
  8734812@192.168.1.17:5060>..Content-Length: 0....                                                                                         
#
U 2014/02/06 22:37:42.898638 192.168.1.17:5060 -> 91.121.129.20:5060
  INVITE sip:0148734812@sip.ovh.fr SIP/2.0..Via: SIP/2.0/UDP 89.83.76.95:5060;branch=z9hG4bK613e9465;rport..Max-Forwards: 70..From: "400" <s
  ip:0033183626986@sip.ovh.fr>;tag=as04af75a1..To: <sip:0148734812@sip.ovh.fr>..Contact: <sip:0033183626986@89.83.76.95:5060>..Call-ID: 0b47
  84ac3a062ee653620cd871778558@sip.ovh.fr..CSeq: 102 INVITE..User-Agent: Asterisk PBX 10.7.0..Date: Thu, 06 Feb 2014 21:37:42 GMT..Allow: IN
  VITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH..Supported: replaces, timer..Content-Type: application/sdp..Conte
  nt-Length: 282....v=0..o=root 393661433 393661433 IN IP4 89.83.76.95..s=Asterisk PBX 10.7.0..c=IN IP4 89.83.76.95..t=0 0..m=audio 19658 RT
  P/AVP 8 0 101..a=rtpmap:8 PCMA/8000..a=rtpmap:0 PCMU/8000..a=rtpmap:101 telephone-event/8000..a=fmtp:101 0-16..a=silenceSupp:off - - - -..
  a=ptime:20..a=sendrecv..                                                                                                                  
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U 2014/02/06 22:37:42.947996 91.121.129.20:5060 -> 192.168.1.17:5060
  SIP/2.0 100 Trying..Call-ID: 0b4784ac3a062ee653620cd871778558@sip.ovh.fr..CSeq: 102 INVITE..From: "400" <sip:0033183626986@sip.ovh.fr>;tag
  =as04af75a1..To: <sip:0148734812@sip.ovh.fr>..Via: SIP/2.0/UDP 192.168.1.17:5060;received=89.83.76.95;rport=5060;branch=z9hG4bK613e9465..C
  ontent-Length: 0....                                                                                                                      
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U 2014/02/06 22:37:42.949698 91.121.129.20:5060 -> 192.168.1.17:5060
  SIP/2.0 407 authentication required..Call-ID: 0b4784ac3a062ee653620cd871778558@sip.ovh.fr..Contact: <sip:0148734812@10.7.1.65:5060;user=ph
  one>..CSeq: 102 INVITE..From: "400" <sip:0033183626986@sip.ovh.fr>;tag=as04af75a1..Proxy-Authenticate: Digest realm="sip.ovh.fr",nonce="01
  3e57263f539e796f6a535b65ff764a",opaque="013e1aee5c41172",stale=false,algorithm=MD5..Record-Route: <sip:91.121.129.20:5060;transport=udp;lr
  >..To: <sip:0148734812@sip.ovh.fr>;tag=00-08179-013e572f-12feeb5f1..Via: SIP/2.0/UDP 192.168.1.17:5060;received=89.83.76.95;rport=5060;bra
  nch=z9hG4bK613e9465..Allow: UPDATE,REFER,INFO..Server: Cirpack/v4.56 (gw_sip)..Content-Length: 0....                                      
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U 2014/02/06 22:37:42.949850 192.168.1.17:5060 -> 91.121.129.20:5060
  ACK sip:0148734812@sip.ovh.fr SIP/2.0..Via: SIP/2.0/UDP 89.83.76.95:5060;branch=z9hG4bK613e9465;rport..Max-Forwards: 70..From: "400" <sip:
  0033183626986@sip.ovh.fr>;tag=as04af75a1..To: <sip:0148734812@sip.ovh.fr>;tag=00-08179-013e572f-12feeb5f1..Contact: <sip:0033183626986@89.
  83.76.95:5060>..Call-ID: 0b4784ac3a062ee653620cd871778558@sip.ovh.fr..CSeq: 102 ACK..User-Agent: Asterisk PBX 10.7.0..Content-Length: 0...
  .                                                                                                                                         
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U 2014/02/06 22:37:42.950101 192.168.1.17:5060 -> 91.121.129.20:5060
  INVITE sip:0148734812@sip.ovh.fr SIP/2.0..Via: SIP/2.0/UDP 89.83.76.95:5060;branch=z9hG4bK18176b4a;rport..Max-Forwards: 70..From: "400" <s
  ip:0033183626986@sip.ovh.fr>;tag=as04af75a1..To: <sip:0148734812@sip.ovh.fr>..Contact: <sip:0033183626986@89.83.76.95:5060>..Call-ID: 0b47
  84ac3a062ee653620cd871778558@sip.ovh.fr..CSeq: 103 INVITE..User-Agent: Asterisk PBX 10.7.0..Proxy-Authorization: Digest username="00331836
  26986", realm="sip.ovh.fr", algorithm=MD5, uri="sip:0148734812@sip.ovh.fr", nonce="013e57263f539e796f6a535b65ff764a", response="c6a71c82d0
  1fcc04dc64686f64b0e2ec", opaque="013e1aee5c41172"..Date: Thu, 06 Feb 2014 21:37:42 GMT..Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, S
  UBSCRIBE, NOTIFY, INFO, PUBLISH..Supported: replaces, timer..Content-Type: application/sdp..Content-Length: 282....v=0..o=root 393661433 3
  93661434 IN IP4 89.83.76.95..s=Asterisk PBX 10.7.0..c=IN IP4 89.83.76.95..t=0 0..m=audio 19658 RTP/AVP 8 0 101..a=rtpmap:8 PCMA/8000..a=rt
  pmap:0 PCMU/8000..a=rtpmap:101 telephone-event/8000..a=fmtp:101 0-16..a=silenceSupp:off - - - -..a=ptime:20..a=sendrecv..                 
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