ITP (C2800 C2650XM) SACK problem

Unanswered Question
Sep 1st, 2008
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Dear Friends,

I encountered the M3UA problem on ITP. If enable multi-instance, the latency for ITP response SACK to ASP is almost 190ms. So ASP will resend the message. But if I disable multi-instance, ITP send SACK is shortly, ASP will not resend message to ITP.

ASP1(192.168.22.226)-------ITP(192.168.22.119)------ASP2(192.168.22.192)

Send message from ASP1 to ASP2. ITP perform GTT routing.

Here is captured log for enable Muli-instance:

Enable multi-instance

1. ASP send message to ITP

517 2008-09-01 15:48:57.788003 226 2905 119 2905 GSM MAP invoke sendRoutingInfoForSM 206


Frame 517 (206 bytes on wire, 206 bytes captured)

Ethernet II, Src: SunMicro_f9:f3:31 (00:03:ba:f9:f3:31), Dst: Cisco_9b:c3:e0 (00:06:28:9b:c3:e0)

Internet Protocol, Src: 192.168.22.226 (192.168.22.226), Dst: 192.168.22.119 (192.168.22.119)

Stream Control Transmission Protocol, Src Port: m3ua (2905), Dst Port: m3ua (2905)

DATA chunk(ordered, complete segment, TSN: 2641167330, SID: 1, SSN: 0, PPID: 3, payload length: 144 bytes)


2. ASP resend message to ITP (wait almost 190ms)


518 2008-09-01 15:48:57.978148 226 2905 119 2905 GSM MAP invoke sendRoutingInfoForSM 206

Frame 518 (206 bytes on wire, 206 bytes captured)

Ethernet II, Src: SunMicro_f9:f3:31 (00:03:ba:f9:f3:31), Dst: Cisco_9b:c3:e0 (00:06:28:9b:c3:e0)

Internet Protocol, Src: 192.168.22.226 (192.168.22.226), Dst: 192.168.22.119 (192.168.22.119)

Stream Control Transmission Protocol, Src Port: m3ua (2905), Dst Port: m3ua (2905)

DATA chunk(ordered, complete segment, TSN: 2641167330, SID: 1, SSN: 0, PPID: 3, payload length: 144 bytes)

3. ITP response SACK to ASP


519 2008-09-01 15:48:57.980143 192.168.22.119 2905 192.168.22.226 2905 SCTP SACK 62

Frame 519 (62 bytes on wire, 62 bytes captured)

Ethernet II, Src: Cisco_9b:c3:e0 (00:06:28:9b:c3:e0), Dst: SunMicro_f9:f3:31 (00:03:ba:f9:f3:31)

Internet Protocol, Src: 192.168.22.119 (192.168.22.119), Dst: 192.168.22.226 (192.168.22.226)

Stream Control Transmission Protocol, Src Port: m3ua (2905), Dst Port: m3ua (2905)

SACK chunk (Cumulative TSN: 2641167330, a_rwnd: 64000, gaps: 0, duplicate TSNs: 0)


Here is captured log for disable Multi-instance:

disenable multi-instance

1. ASP send message to ITP


1301 2008-09-01 15:56:41.013510 226 2905 119 2905 GSM MAP invoke sendRoutingInfoForSM 198

Frame 1301 (198 bytes on wire, 198 bytes captured)

Ethernet II, Src: SunMicro_f9:f3:31 (00:03:ba:f9:f3:31), Dst: Cisco_9b:c3:e0 (00:06:28:9b:c3:e0)

Internet Protocol, Src: 192.168.22.226 (192.168.22.226), Dst: 192.168.22.119 (192.168.22.119)

Stream Control Transmission Protocol, Src Port: m3ua (2905), Dst Port: m3ua (2905)

DATA chunk(ordered, complete segment, TSN: 1828169395, SID: 1, SSN: 0, PPID: 3, payload length: 136 bytes)

......

2. ITP response SACK (almost 30ms)


1302 2008-09-01 15:56:41.044919 119 2905 226 2905 GSM MAP SACK returnResultLast sendRoutingInfoForSM 226

Frame 1302 (226 bytes on wire, 226 bytes captured)

Ethernet II, Src: Cisco_9b:c3:e0 (00:06:28:9b:c3:e0), Dst: SunMicro_f9:f3:31 (00:03:ba:f9:f3:31)

Internet Protocol, Src: 192.168.22.119 (192.168.22.119), Dst: 192.168.22.226 (192.168.22.226)

Stream Control Transmission Protocol, Src Port: m3ua (2905), Dst Port: m3ua (2905)

SACK chunk (Cumulative TSN: 1828169395, a_rwnd: 64000, gaps: 0, duplicate TSNs: 0)

DATA chunk(ordered, complete segment, TSN: 1908210121, SID: 1, SSN: 0, PPID: 3, payload length: 148 bytes)

**************************************

My question is:

1. If enable multi-instance on ITP, how to improve ITP response SACK packet in 100ms to ASP? I checked the CPU utilization, it was not exceed 10%.

2. ITP response SACK more than 190ms, is normal?

Thanks and regards,

Jeffrey


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jsivulka Fri, 09/05/2008 - 13:47
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found a document about the similar problem between Cisco PGW and ITP



http://www.cisco.com/en/US/partner/products/hw/vcallcon/ps2152/products_tech_note09186a00802119b9.shtml#troubleshoot


There is no problem with the BEAT message you included, and the ITP responded properly with BEAT ACK. The "No Message Parameters" text is simply debug output indicating that there are no parameters included with this message....that is *NOT* an error.


jefferyshi Mon, 09/22/2008 - 01:05
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Hi

Thansk for replay.

I mean the selective ack (know as “delayed ack”) message response to ASP was too slow after enable multi-instance.

I try to modify the delayed SACK value to 40ms that recommend for the Telecoms industry on ITP. But the minimum is 100ms.

cumulative-sack msec

Range is 100 through 500 milliseconds. The default is 200 milliseconds.

So I set to 100ms.

I found every SACK latency for data chunk to ASP was between 90ms to 106ms. And don't see duplicate data chunk from ASP, the problem has been resolved. By the way the network latency from ITP to ASP is within 1ms to 6ms.


Thanks

Jeffrey


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