Please refer to Figure 7.1 below, which shows the setup for the following two submission experiments in detail. The experimental setup involves:
At Site One:
At Site Two:
The two setups are linked to each other over a number of routers across the Internet.
In both cases below, we are interested exclusively in analyzing the recorded data between the sender laptop and the Unix mail server (in the case of SMTP submission), or the EMSD Message Test Center (in the case of EMSD submission). Thus the "receiver" shown below, although necessary to submit the message, does not enter into our study picture directly.
Message was submitted from the Laptop to the Unix mail server. To submit a message from the laptop, Netscape's Mail User Agent on Windows 3.1 was utilized. From the file menu on Netscape, "New Mail Message" was selected, popping up a mail window. The message was typed in, a recipient (the "receiver" in Figure 7.1) was specified, and "Send" was then clicked. The sniffer recorded the exchange of data between the sender and the mail server that was <nwestmail.nwest.airdata.com> implementing sendmail.
The following is the protocol trace recorded by the sniffer. After TCP synchronization and acknowledgment, a virtual circuit is established between the sender's Netscape Mail User Agent and sendmail on the mail server, and data is exchanged after specifying the sender and recipient addresses.
IP_PDU MailServer UA DATA TCP IP -------------------------------------------------------------------- 1 TCP .<------- TCP SYN -------- . 0 24 44 2 TCP . ------- TCP SYN ack ---->. 0 24 44 3 TCP .<------- Push ACK ------- . 0 20 40 (128) 4 SMTP . ----220 server ready --->. 116 136 156 5 TCP .<------- Push ACK ------- . 0 20 40 (196) 6 SMTP .<------- HELO <client>--- . 36 56 76 7 SMTP . ----250 server Hello --->. 111 131 151 8 TCP .<------- Push ACK ------- . 0 20 40 (267) 9 SMTP .<--MAIL FROM:<sender> --- . 32 52 72 10 SMTP . ----250 ... Sender ok--->. 39 59 79 11 TCP .<------- Push ACK ------- . 0 20 40 (191) 12 SMTP .<--RCPT TO:<rcpt>-------- . 33 53 73 13 SMTP .<----250...Recipient ok-- . 45 65 85 14 TCP .<------- Push ACK ------- . 0 20 40 (198) 15 SMTP .<------ "DATA" ---------- . 6 26 46 16 TCP . ------- ACK ------------>. 0 20 40 (86) 17 SMTP . ----354..end with "."--->. 50 70 90 18 TCP .<------- Push ACK ------- . 0 20 40 (130) 19 SMTP .<--Mail header+body ----- . 437 457 477 20 SMTP .<------ . --------------- . 5 25 45 21 TCP . ------- ACK ------------>. 0 20 40 (562) 22 SMTP . ------- 250 Ok --------->. 8 28 48 23 TCP .<------- Push ACK ------- . 0 20 40 24 TCP .<------- Push Reset ----- . 0 20 40 (128) ----------------------------------------------------------------------
Total IP Packet bytes: 1886 Message Length (header + body): 437 Total Overhead (TCP header + IP header): 1449 3.1.4 Message as Received Message-ID: <32249501.46FD@airdata.com> Date: Wed, 28 Aug 1996 11:50:41 -0700 From: Jia-bing Cheng <jcheng@airdata.com> Organization: AT&T Wireless Services X-Mailer: Mozilla 2.0 (Win16; U) MIME-Version: 1.0 To: j.cheng@pocketnet.net Subject: test3 X-URL: file:///c:/netscape/jbc.htm Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit 123456789012345678901234567890 12345678901234567890 1234567890
The message was submitted from the laptop using Neda's EMSD Mail User Agent version 0.9 on Windows 3.1, to Neda's EMSD Message Test Center. EMSD-Pine version 3.91 was used to submit the message from the laptop. After invoking Pine, and typing "C", a new message was composed and then sent via <CTRL X>. A direct connection was then established between the EMSD Mail User Agent on the laptop and the EMSD Message Test Center, and the message was relayed. The sniffer recorded exchange of data between the sender and Neda's EMSD Message Test Center which was <emsd.neda.com> implementing ESROS.
The following is the protocol trace recorded by the sniffer. As compared to the SMTP protocol trace in section 7.3.1, you can see the exchange is quite brief.
IP_PDU MailServer UA DATA UDP IP --------------------------------------------------------------- 1 UDP .<--Invoke header+body --- . 206 214 234 2 UDP . -----Response ---------->. 15 23 43 3 UDP .<------- Ack ------------ . 2 10 30 ---------------------------------------------------------------
Total IP Packet bytes: 307
Message Length (header + body): 206
Total Overhead (EMSD header + UDP header + IP header): 101
Total IP bytes in the case of EMSD submission as compared to SMTP submission is down by a factor of 6; the header count is down by a factor of 2.6; and total overhead is down by a factor of 14, representing major savings in data traffic.
The # text below is provided as comments and does not appear in the received message.
P.!.0. ... 0..0z@."333. 333"<test1@emsd. neda.com> # FROM: 010/@)Jia-bing-pn Cheng<j.cheng@pocketnet.net> # RCPT: ......test4 # Subject: ....text/plain; charset=us-ascii # content-type 0C.A # 123456789012345678901234567890. # BODY: 12345679801234567890. 1234567890
