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High number of drops Tx

eXPlosion_
Advisor

High number of drops Tx

Hi,

we have HP J4850A switch which is connected to HP J4813 switch.

 

On J4850A one port it started to increment Tx drops

Link Status : Up
Totals (Since boot or last clear) :
Bytes Rx : 976,360,732 Bytes Tx : 2,506,637,830
Unicast Rx : 1,172,767,162 Unicast Tx : 1,326,163,045
Bcast/Mcast Rx : 76,715,462 Bcast/Mcast Tx : 1,110,624,465
Errors (Since boot or last clear) :
FCS Rx : 0 Drops Tx : 85,552,528
Alignment Rx : 0 Collisions Tx : 0
Runts Rx : 0 Late Colln Tx : 0
Giants Rx : 0 Excessive Colln : 0
Total Rx Errors : 0 Deferred Tx : 0
Rates (5 minute weighted average) :
Total Rx (bps) : 637568 Total Tx (bps) : 27428392
Unicast Rx (Pkts/sec) : 151 Unicast Tx (Pkts/sec) : 712
B/Mcast Rx (Pkts/sec) : 0 B/Mcast Tx (Pkts/sec) : 1652
Utilization Rx : 00.05 % Utilization Tx : 02.25 %

 

IPTV users are experiencing problems 

What is the cause of this? Utilization is only 2% but monitoring shows 20% utilization.

Duplex is full, speed is 100 on both sides.

5 REPLIES
Michael Patmon
Trusted Contributor

Re: High number of drops Tx

Do you have bursts of greater than 100Mbps trying to egress that port?  Typically TX drops are due to oversubscription of the egress port.  

eXPlosion_
Advisor

Re: High number of drops Tx

How can i check for bursts?

Michael Patmon
Trusted Contributor

Re: High number of drops Tx

Good question.  I just meant if you knew of clients that were doing bandwidth intensive things across that link (like file transfers) you were probably experiencing periodic oversubscription, and TX drops would is a symptom of that.  A 100Mbps link would not be very hard to oversubscribe.

 

To protect your IPTV streams from being starved by bulk data transfers you could add QoS policy for the video stream(s).  You could also add a trunk (link aggregation) between the two switches for more bandwidth.

 

 

 

 

eXPlosion_
Advisor

Re: High number of drops Tx

Sorry for late reply.

Both switches do not support QoS at all.

Michael Patmon
Trusted Contributor

Re: High number of drops Tx

The 5300 does.  If your IPTV streams run on a specific UDP port you could bump the priority of it.  It should then get prioritized on egress over normal traffic.

5300XL(config)# qos ?
udp-port               Set UDP port based priority.
tcp-port               Set TCP port based priority.
device-priority        Configure device-based priority.
dscp-map               Define mapping between a DSCP (Differentiated-Services Codepoint) value and an 802.1p priority.
protocol               Configure protocol-based priority.
type-of-service        Configure the Type-of-Service method the device uses to prioritize IP traffic.

So you could then do::

5300XL(config)# qos udp-port 5000 priority 7