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Rx Discards in the switch

 
Ramzah_Rehman
Occasional Advisor

Rx Discards in the switch

I have two servers connected to a 2930F ARUBA HPE hardware switch via 10Gbps QSFP+ cables. I generated UDP traffic (1470 byte datagrams) from one sever to the other. When I send traffic at 10Gbps rate in this 10Gbps network, the switch shows very high Rx Discards on ingress port. Also, the throughput drops to 0 after 1 or 2 seconds. When I send traffic at 1Gbps rate in this 10Gbps network, the throughput achieved is 1Gbps and there is no Rx discard. I think the issue is that the port buffer size of switch is gettingbottleneckedif so is there are way in increase port's share of packet buffer. Could there be any other reason?
3 REPLIES 3
parnassus
Honored Contributor

Re: Rx Discards in the switch

Hi!

Just to contextualize...can you show us involved interfaces' detailed status included transceivers used? remove any serial number (if any will appear on the outputs)

Use those commands (note that X is the port's id):

show interfaces transceiver ethernet X 

show interfaces transceiver ethernet X detail

show interfaces ethernet X

Ramzah_Rehman
Occasional Advisor

Re: Rx Discards in the switch

I was sending 64K sized UDP datagrams earlier and was getting some throughput that quickly dropped to zero in 2 seconds. Now I am sending 1500 size UDP datagrams (to avoid the issues associated with fragmentation). The throughput achieved on the receiver is around 4Gbps. It never exceeds it. I am sending traffic at 10Gbps. These are the results I got. Please note that port 25 is the port connected to the sender and port 27 is the port connected to the receiver.

$sh interfaces transceiver ethernet 25

 

Transceiver Technical Information:

 

                     Product      Serial             Part

 Port    Type        Number       Number             Number

 ------- ----------- ------------ ------------------ ----------

 25      SFP+DA3     J9283D       CN80KC06Z0         8121-1298

 

$sh interfaces transceiver ethernet 25 detail

 

Transceiver in 25

   Interface Index    : 25

   Type               : SFP+DA3

   Model              : J9283D

   Connector Type     : Vendor specific

   Wavelength         : n/a

   Transfer Distance  : 3m (copper),

   Diagnostic Support : None

   Serial Number      : CN80KC06Z0

$ sh interfaces ethernet 25

 

 Status and Counters - Port Counters for port 25

 

  Name  :

  MAC Address      : 548028-5c79a7

  Link Status      : Up

  Port Enabled     : Yes

  Totals (Since boot or last clear) :

   Bytes Rx        : 1,656,209,115        Bytes Tx        : 4,334

   Unicast Rx      : 6,825,804            Unicast Tx      : 15

   Bcast/Mcast Rx  : 12                   Bcast/Mcast Tx  : 11

  Errors (Since boot or last clear) :

   FCS Rx          : 0                    Drops Tx        : 0

   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

  Others (Since boot or last clear) :

   Discard Rx      : 2,765,975            Out Queue Len   : 0

   Unknown Protos  : 0

  Rates (5 minute weighted average) :

   Total Rx(Kbps) : 209,944                Total Tx(Kbps) : 0

   Unicast Rx (Pkts/sec) : 11,782         Unicast Tx (Pkts/sec) : 0

   B/Mcast Rx (Pkts/sec) : 0              B/Mcast Tx (Pkts/sec) : 0

   Utilization Rx  : 02.09 %              Utilization Tx  :     0 %

 

$sh interfaces transceiver ethernet 27

 

Transceiver Technical Information:

 

                     Product      Serial             Part

 Port    Type        Number       Number             Number

 ------- ----------- ------------ ------------------ ----------

 27      SFP+DA3     J9283D       CN80KC051F         8121-1298

 

$sh interfaces transceiver ethernet 27 detail

 

Transceiver in 27

   Interface Index    : 27

   Type               : SFP+DA3

   Model              : J9283D

   Connector Type     : Vendor specific

   Wavelength         : n/a

   Transfer Distance  : 3m (copper),

   Diagnostic Support : None

   Serial Number      : CN80KC051F

 

$sh interfaces ethernet 27

 

 Status and Counters - Port Counters for port 27

 

  Name  :

  MAC Address      : 548028-5c79a5

  Link Status      : Up

  Port Enabled     : Yes

  Totals (Since boot or last clear) :

   Bytes Rx        : 2,495                Bytes Tx        : 1,757,960,777

   Unicast Rx      : 15                   Unicast Tx      : 6,825,804

   Bcast/Mcast Rx  : 13                   Bcast/Mcast Tx  : 13

  Errors (Since boot or last clear) :

   FCS Rx          : 0                    Drops Tx        : 0

   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

  Others (Since boot or last clear) :

   Discard Rx      : 0                    Out Queue Len   : 0

   Unknown Protos  : 0

  Rates (5 minute weighted average) :

   Total Rx(Kbps) : 0                      Total Tx(Kbps) : 131,344

   Unicast Rx (Pkts/sec) : 0              Unicast Tx (Pkts/sec) : 10,672

   B/Mcast Rx (Pkts/sec) : 0              B/Mcast Tx (Pkts/sec) : 0

   Utilization Rx  :     0 %              Utilization Tx  : 01.31 %

 

 

 

Ramzah_Rehman
Occasional Advisor

Re: Rx Discards in the switch

My hunch is that it's the issue with buffer sizes. Is there a way to allocate more buffer size to 10G ports? Well, interestingly, total packet buffer occupancy of the switch stays at 34% whether any traffic is flowing through the switch or not.