Protx TCP communications issue

Protx's server stops talking partway through the TCP session.

[simonwheatley]

Our ecommerce application collects the card details from the customer, URL encodes them, and POSTs them to Protx over an SSL ecrypted session, Protx then reply with a message from the acquiring bank saying yay or nay. So far so good.

The issue exists at a TCP level. Our server successfully initiates the SSL session with Protx and begins to transmit the applicatino data. A couple of packets into the transmitting the application data, all communication from Protx ceases. A rough example of what I see in a TCP dump of the relevant network traffic is below, after packet (#) number 14 we see no further communication from Protx. Because we get no reply, we are unable to confirm the transaction, unable to place the order and the customer has to try again. Interestingly although we receive no communication from Protx, they are still listening to us and do process the transaction; i.e. the card get's authorised, or the payment taken, etc.

We've seen this issue over two periods of time, the first stretching over 2.5 weeks from 27 July and the second started at 16:38 GMT yesterday (18 Aug). The disappearance of the issue was attributed to a change in their DDOS mitigation systems; you may be aware that Protx underwent a very heavy DDOS attack earlier this year.

Any advice would be gratefully received.

Thanks in advance,

Simon

#,  Source, Destination, Protocol, Info 
1,  Us,  Protx,  TCP,  1867 > https [SYN] Seq=0 Ack=0 Win=5840 Len=0 MSS=1460 TSV=119597247 TSER=0 WS=2 
2,  Protx, Us,   TCP,  https > 1867 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 
3,  Us,  Protx,  TCP,  1867 > https [ACK] Seq=1 Ack=1 Win=5840 Len=0, 
4,  Us,  Protx,  SSLv2,  Client Hello 
5,  Protx, Us,   TLS,  Server Hello 
6,  Protx, Us,   TLS,  Continuation Data 
7,  Us,  Protx,  TCP,  1867 > https [ACK] Seq=127 Ack=1381 Win=8280 Len=0, 
8,  Us,  Protx,  TCP,  1867 > https [ACK] Seq=127 Ack=2254 Win=11040 Len=0 
9,  Us,  Protx,  TLS,  Client Key Exchange 
10,  Protx, Us,   TLS,  Change Cipher Spec 
11,  Us,  Protx,  TCP,  1867 > https [ACK] Seq=309 Ack=2297 Win=11040 Len=0 
12,  Us,  Protx,  TLS,  Application Data, 
13,  Protx, Us,   TCP,  https > 1867 [ACK] Seq=2297 Ack=379 Win=7902 Len=0 
14,  Us,  Protx,  TLS,  Application Data 
15,  Us,  Protx,  TLS,  [TCP Retransmission] Application Data 
16,  Us,  Protx,  TLS,  [TCP Retransmission] Application Data 
17,  Us,  Protx,  TLS,  [TCP Retransmission] Application Data 
18,  Us,  Protx,  TLS,  [TCP Retransmission] Application Data 
19,  Us,  Protx,  TLS,  [TCP Retransmission] Application Data 
20,  Us,  Protx,  TLS,  [TCP Retransmission] Application Data 
21,  Us,  Protx,  TLS,  [TCP Retransmission] Application Data 
22,  Us,  Protx,  TLS,  [TCP Retransmission] Application Data 
23,  Us,  Protx,  TLS,  Encrypted Alert 

[edited by: txbakers at 5:08 pm (utc) on Aug. 19, 2005]
[edit reason] no specific URLs - thanks. [/edit]