Wireshark-users: Re: [Wireshark-users] wireshark shows: TCP Port numbers reused on PlanetLab node
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From: Martin Visser <martinvisser99@xxxxxxxxx>
Date: Sat, 23 Mar 2013 23:26:47 +1100
Jaap, yes, as a networking consultant over the years I have on many occasions had to check and double-check when speaking to colleagues and customers about exactly what the specifics are of the physical connections they are referring to.

Just the word "trunk" (as you have seen from WP) is totally ambiguous. (Apart from bonding/teaming/aggregation, trunk is also often used for 802.1q capable links). 



On 23 March 2013 22:00, Jaap Keuter <jaap.keuter@xxxxxxxxx> wrote:

Talking about a cacophony of terms. From Wikipedia:
------------------------8<---------------------------------
In addition to the IEEE link aggregation substandards [802.3ad, 802.1ax], there
are a number of proprietary aggregation schemes including Cisco's EtherChannel
and Port Aggregation Protocol, AVAYA's Multi-Link Trunking, Split Multi-Link
Trunking, Routed Split Multi-Link Trunking and Distributed Split Multi-Link
Trunking, ZTE's "Smartgroup", or Huawei's "EtherTrunk". Most high-end network
devices support some kind of link aggregation, and software-based
implementations – such as the *BSD lagg package, Linux' bonding driver, Solaris'
dladm etc. – also exist for many operating systems.
------------------------8<---------------------------------
http://en.wikipedia.org/wiki/Link_aggregation

Thanks,
Jaap


On 03/22/2013 12:09 PM, Sake Blok wrote:
> A teamed physical interface is when you combine two network cards into one
> logical network card. Cisco calls it Etherchannel, other network vendors call it
> trunking and linux calls it bonding while in is called teaming in the windows world.
>
> Of course the SYN/ACK could not have been on the network before the SYN to which
> it was a response, therefor for some reason the capture process saw the SYN/ACK
> earlier than the SYN. This can be caused by using two network interfaces for the
> same TCP session. As the timestamping is done in the OS and not on the network card.
>
> Cheers,
> Sake
>
> On 22 mrt 2013, at 10:48, wen lui wrote:
>
>> what do you mean for this : " a teamed physical interface"
>> there are many virtual machines in one PlanetLab nodes, are there any
>> implications?
>>
>> but from the time, the second packet arrives at a minus time, it means it
>> arrives earlier than the first?
>>
>> I don't know why they are out order? any reasons?
>>
>> 2013/3/21 Martin Visser <martinvisser99@xxxxxxxxx
>> <mailto:martinvisser99@xxxxxxxxx>>
>>
>>     Very simply, you have have captured the packets 1 and 2 out of order.
>>     Packet 2 it would seem is the SYN,  that initiated the SYN-ACK in packet
>>     1. (At least it seems that way to me - a sane stack wouldn't reuse the
>>     same TCP source port at such a small interval). Are you running a teamed
>>     physical interface, and hence why you are capturing packets out of order?.
>>
>>     Regards, Martin
>>
>>     MartinVisser99@xxxxxxxxx <mailto:MartinVisser99@xxxxxxxxx>
>>
>>
>>     On 21 March 2013 00:18, wen lui <esolvepolito@xxxxxxxxx
>>     <mailto:esolvepolito@xxxxxxxxx>> wrote:
>>
>>         I run a simple TCP client on machine A and a simple TCP server on
>>         machine B (machine B is a Planetlab node while machine A is not).
>>         Then the client establishes a tcp connection with machine B and send
>>         some data.
>>         I capture packets on both A and B, on A the wireshark shows that it is
>>         a normal 3-Way handshaking, but on B, it shows as below:
>>
>>         |1   0.000000        138.46.116.22   138.46.201.109  TCP     74      54000 > 57182 [SYN, ACK] Seq=0 Ack=0 Win=5792 Len=0 MSS=1460 SACK_PERM=1 TSval=1751648211 TSecr=1119925943 WS=128 0.000000
>>
>>
>>
>>         2    -0.000062       138.46.201.109  138.46.116.22   TCP     74      [TCP Port numbers reused] 57182 > 54000 [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=1119925943 TSecr=0 WS=128        -0.000062
>>         3    0.000308        138.46.201.109  138.46.116.22   TCP     66      57181 > 54000 [ACK] Seq=1 Ack=1 Win=14720 Len=0 TSval=1119737278 TSecr=1751459556       0.000308
>>
>>
>>
>>         |
>>         while I see on machine B, actually the tcp connection is established.
>>         before the client sends the SYN and ACK, I checked machine B and found no TCP connection
>>
>>         |netstat -tnp
>>         (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.)
>>         Active Internet connections (w/o servers)
>>         Proto Recv-Q Send-Q Local Address               Foreign Address                State       PID/Program name
>>         tcp        0      0 138.46.116.22:54000 <http://138.46.116.22:54000/>         138.46.201.109:57181 <http://138.46.201.109:57181/>        ESTABLISHED 17879/tcp_server
>>
>>
>>
>>         anyway, I can send data to the tcp server and it receives it correctly.
>>
>>
>>         ||
>>         why wireshark shows TCP Port numbers reused? and the time is '-0.000062'? |
>>
>>

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