Sigtran IP Links Are Fluctuating

Asset ID:	1-72-2218053.1
Update Date:	2017-01-10
Keywords:

Solution Type Problem Resolution Sure

Solution 2218053.1 : Sigtran IP Links Are Fluctuating

Applies to:

Oracle Communications EAGLE (Software) - Version EAGLE 3x.x and later
Information in this document applies to any platform.

Symptoms

Sigtran links to DPC 2017 are fluctuating from both mated STP's.
DPC:- 2017
lsn:- lsn01 from STP01
lsn02 from STP02

Cause

There is a configuration mismatch regarding the association on both ends.
It may create some failures at the SCTP Layer.

Also :

1. Here is an extract of the times when the ASP became down :

> pass:loc=4116:cmd="linkinfo -l a"

stp01 16-12-19 18:07:17 EAGLE5 46.2.0-67.10.0
16-12-16 14:24:54.180 ASP_DOWN
16-12-16 17:07:36.685 ASP_DOWN
16-12-17 06:42:03.430 ASP_DOWN
16-12-17 11:57:51.635 ASP_DOWN
16-12-17 20:30:33.705 ASP_DOWN
16-12-19 09:55:12.910 ASP_DOWN
16-12-19 11:03:19.700 ASP_DOWN

It happened several times since the 16th of December

2. There are many retransmissions on the association :

> rept-stat-card:loc=4116:mode=full

stp01 16-12-19 18:08:18 EAGLE5 46.2.0-67.10.0
CARD VERSION TYPE GPL PST SST AST
4116 137-010-000 E5ENET IPSG IS-NR Active -----
ALARM STATUS = No Alarms.
...
ASSOCIATION STATUS
ANAME PST SST
assoc01 IS-ANR EXCESS RETRANS
assoc02 OOS-MT CONNECTING

Association statistics reseted at 18:18 :

> pass:loc=4116:cmd="sctp -a ttimsnod02 -r"
stp01 16-12-19 18:18:07 EAGLE5 46.2.0-67.10.0

And only 4 minutes later, there was again retransmission :

> pass:loc=4116:cmd="sctp -a assoc01"
stp01 16-12-19 18:22:35 EAGLE5 46.2.0-67.10.0
..
retransmit data chunks sent = 382
retransmit timer count = 164
consecutive retransmit timeouts = 22
RTO between RMIN and RMAX inclusive = 1228

The RTO was 1228 times higher than the RMIN, it means there are maybe some delay on the path.

Solution

The thing to fix this is the configuration issue, on Eagle this is unihomed and the far end is mutlihomed. You should also have multihomed on Eagle side.

> rtrv-assoc:aname=assoc01

stp01 16-12-19 18:10:31 EAGLE5 46.2.0-67.10.0
  ANAME assoc01
  LOC 4116 IPLNK PORT A LINK A
  ADAPTER M3UA VER M3UA RFC
  LHOST lhost01
  ALHOST ---
  RHOST rhost01
  ARHOST rhost02

Conclusion : This is not an issue on Eagles side, the IP network or the far end have to be troubleshooted

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