> tcpdump -pnvvvvvi re0 host 172.16.3.23 and port 23
tcpdump: listening on re0, link-type EN10MB (Ethernet), capture size 96 bytes
1	13:48:01.904328 IP (tos 0x10, ttl 64, id 39041, offset 0, flags [DF], proto TCP (6), length 60, bad cksum 0 (->4c8d)!)
    213.108.209.9.57519 > 172.16.3.23.23: Flags [S], cksum 0x55cc (incorrect -> 0x4f06), seq 1287426781, win 65535, options [mss 1460,nop,wscale 3,sackOK,TS val 2271566746 ecr 0], length 0
2	13:48:01.907557 IP (tos 0x0, ttl 61, id 61012, offset 0, flags [none], proto TCP (6), length 60)
    172.16.3.23.23 > 213.108.209.9.57519: Flags [S.], cksum 0x0c40 (correct), seq 4031151362, ack 1287426782, win 8192, options [mss 1460,nop,wscale 0,nop,nop,TS val 178285 ecr 2271566746], length 0
3	13:48:01.907579 IP (tos 0x10, ttl 64, id 39043, offset 0, flags [DF], proto TCP (6), length 52, bad cksum 0 (->4c93)!)
    213.108.209.9.57519 > 172.16.3.23.23: Flags [.], cksum 0x55c4 (incorrect -> 0x377b), seq 1, ack 1, win 8326, options [nop,nop,TS val 2271566749 ecr 178285], length 0
4	13:48:01.908813 IP (tos 0x10, ttl 64, id 39045, offset 0, flags [DF], proto TCP (6), length 85, bad cksum 0 (->4c70)!)
    213.108.209.9.57519 > 172.16.3.23.23: Flags [P.], seq 1:34, ack 1, win 8326, options [nop,nop,TS val 2271566751 ecr 178285], length 33 [telnet WILL AUTHENTICATION, DO ENCRYPT, WILL ENCRYPT, DO SUPPRESS GO AHEAD, WILL TERMINAL TYPE, WILL NAWS, WILL TSPEED, WILL LFLOW, WILL LINEMODE, WILL NEW-ENVIRON]
5	13:48:01.917677 IP (tos 0x0, ttl 61, id 61014, offset 0, flags [none], proto TCP (6), length 55)
    172.16.3.23.23 > 213.108.209.9.57519: Flags [P.], cksum 0x1ff8 (correct), seq 1:4, ack 1, win 8192, options [nop,nop,TS val 178285 ecr 2271566749], length 3 [telnet DO TERMINAL TYPE]