Notes of PONG command on Nexus 7000

Mountain view over Devine Trees near Chilan (棲蘭), Yilan County, Taiwan. (棲蘭神木園)

We can use PONG command to measure and and analyze switch port to other switch port latency. Example of using this command can be found on PONG command reference.

----- BEGIN OF EXAMPLE -----

This example shows the Pong service using static MAC for injection:

switch(config)# configure terminal
switch(config)# pong source 1.2.3 destination 18ef.63e9.ee43 .....
 Packet No. 1
 Legend:
                 (*)  - software delay(not hardware latency)
                 (#)  - reverse path
                 (NA) - not available
 --- ------------------------- --------------------------
 Hop   System-mac  (switch-id) Switching time
                               (sec,     nsec)
 --- ------------------------- --------------------------
 1    18-ef-63-e9-ee-41   (NA)   0      4304
 2    18-ef-63-e9-ee-42   (NA)   0      4288
 3    18-ef-63-e9-ee-43   (NA)   0      540653528*
 #4   18-ef-63-e9-ee-42   (NA)   0      4760
 #5   18-ef-63-e9-ee-41   (NA)   0      4816
 Round trip time: 0sec 23984 nsec
 Packet No. 2
 Legend:      

.....

Packet No. 5
 Legend:

.....

 Round trip time: 0sec 24568 nsec
 Summary:
         Packets sent on vlan  : 1
         Total packets sent    : 5
         Total packets received: 5
         Maximum round trip time in ns: 24568
         Minimum round trip time in ns: 23984
         Average round trip time in ns: 24419

----- END OF EXAMPLE -----

Information I learned about PONG

In above example, I have learned the following information.

1. PONG must be typed only in Configuration Mode.
2. Source MAC address can be real MAC address, or even imaginary MAC address, such as in this example: "1.2.3".
3. Destination MAC address should belong to some PONG-supported switches such as Nexus 7000.
4. The precision of timing is in nanoseconds.
5. PONG command can measure round trip time between two switch ports. It can also record "switching" time on each hop and software processing time (normally at the destination switch).
6. PONG command can record round trip hop-by-hop path and display in switch System MAC or FabricPath Switch ID.

Guidelines of PONG

I can only find PONG command on Nexus 7000. I also learned two more information on this page: Using Pong.

1. PONG can NOT live along with PFC. PFC can NOT live along with PFC. They are mutually exclusive.
2. PONG works only on single path round-trip, not on multiple paths.

Relevant content on Using Pong:

Guidelines and Limitations:

• The pong utility can be enabled only on F-Series and M2 module ports.

• On F1 series module ports, the pong utility is not supported on a VDC when priority flow control (PFC) is enabled on any of the ports in the same VDC.

• On F1 series module ports, priority flow control (PFC) is not supported when the pong utility is enabled in the same VDC.

• The pong utility is not supported on an access switch using vPC.

     However, the pong utility is supported when using an interface from the access switch to the vPC peer. 
     For example, to configure the pong utility from  the access switch to the vPC primary, you must provide an interface that is directly connected to the vPC primary.

• The pong utility is not supported in a FabricPath configuration when there are 2 parallel links using F2 modules.

     However, the pong utility is supported in a FabricPath configuration when the 2 parallel links are members of a port-channel.

Requirements to use PONG

Although it is not explicitly defined, I believe it requires the features pong and ptp. See the "Related Commands" section of PONG command reference.

Related Commands

Command	Description
feature pong	Enables the Pong feature.
feature ptp	Enables the Precision Time Protocol (PTP) feature. This command is documented in the Cisco Nexus 7000 Series NX-OS System Management Command Reference, Release 5.x.

References

• PONG command reference
• Using Pong

Cheers!