23:04:01.183748 | Time |
192.168.10.3.1196 > 192.168.10.1.23 | Source/Dest |
: S | Flag Set |
8817917:8817917(0) | Sequence Number |
win 8192 | Window Size |
<mss 1474,nop,nop,sackOK> | Maximum Segment Size |
(DF) | Don't Fragment |
Source/Dest - 192.168.10.3.1196 > 192.168.10.1.23
The source ports (client) are initiated from a value of 1024 or greater. The destination (server) has a destination of 1023 or less, commonly defined as "privleged ports".
S - Flag Set
(P) PSH - Push
(R) RST - Reset
(S) SYN - Synchronization
(F) FIN - Finish
(U) URG - Urgent
(A) ACK - Acknowledgment
Sequence Number - 8817917:8817917(0)
The initial sequence number following the ending number. (0) is the number of bytes in the packet. This first sequence number maintains the correct order of the packets. The initializing host tells the second host where to begin incrementing after the first sequence; sequence numbers are incremented by one for every bite in a packet. Sequence numbers are set in both directions.
Window Size - win 8192
The window size determines how much data may be transferred at a time. Various operating systems can handle packets of different sizes, at multiple speeds. Each host will specify the maximum size of a packet that can be received. Flow control is defined via sending and receiving buffers; and (MSS) maximum segment size. If a host transmits packets over the window size, the server may drop the packets.
Maximum Segment Size - <mss 1474,nop,nop,sackOK>
Defines options that are set when the connection is established. The MSS indicates the maximum size of a segment TCP options must be 32 bit boundaries; if this option is not met NOP's (NoOperation codes) will be used to pad the difrence in zeros.
Don't Fragment - (DF)
Fragmentation is used if the size of the datagram being sent is larger then the maximum size the route can handle. This value is known as (ITU) interface transmission unit. The smallest ITU between a source and destination is the (MTU) maximum transfer unit. Fragmentation is determined by the MTU value on the interface, fragmentation will only occur if required. If packets are fragmented a fragment id and offset will be inplace if the (DF). DF helps ensure packet reassembly.