[Serusers] INVITE format.

Hello list. I have a question not directly related with SER, but i was hoping that someone could give me a hand here. I'm not very familiar with this type of INVITE. INVITE sip:3341876@mydomain.sip.com SIP/2.0 v: SIP/2.0/UDP 10.10.10.241:5060;branch=z9hG4bK2542945499 f: "558100005481" <sip:558100005481@mydomain.sip.com>;tag=1000053237 t: <sip:3341876@mydomain.sip.com> i: 1de74610a4a7dba71ac257ea510065c9(a)10.10.10.241 CSeq: 19 INVITE m: sip:558100005481@10.10.10.241 Max-Forwards: 70 User-Agent: SIP-ICSG302-1.139-icablesystem/v2.0_enabled Allow: INVITE, ACK, OPTIONS, CANCEL, BYE, REFER Supported: timer, replaces c: application/sdp Accept: application/sdp l: 295 v=0 o=558100005481 1123541222 1123541222 IN IP4 10.10.10.241 s=SIP Call t=0 0 m=audio 5094 RTP/AVP 18 4 0 8 103 c=IN IP4 10.10.10.241 a=rtpmap:18 G729/8000 a=rtpmap:4 G723/8000 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 a=rtpmap:103 telephone-event/8000 a=fmtp:103 0-15 a=ptime:20 What format is V: ? , f : ?, i : ?. Are these values according to the RFC? Sorry about this maybe stupid question. Thanks Ricardo.-