Mention Jumbo Frames for VPC MTU (#7221) (#5180)

Signed-off-by: Modular Magician <[email protected]>

Author: modular-magician

.changelog/7221.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+compute: fixed wrong maximum limit description for possible VPC MTUs
+```

google-beta/resource_compute_network.go

@@ -97,8 +97,11 @@ If the field is not speficied, then a /48 range will be randomly allocated from
 				Computed: true,
 				Optional: true,
 				ForceNew: true,
-				Description: `Maximum Transmission Unit in bytes. The minimum value for this field is 1460
-and the maximum value is 1500 bytes.`,
+				Description: `Maximum Transmission Unit in bytes. The default value is 1460 bytes. 
+The minimum value for this field is 1300 and the maximum value is 8896 bytes (jumbo frames).
+Note that packets larger than 1500 bytes (standard Ethernet) can be subject to TCP-MSS clamping or dropped
+with an ICMP 'Fragmentation-Needed' message if the packets are routed to the Internet or other VPCs 
+with varying MTUs.`,
 			},
 			"routing_mode": {
 				Type:         schema.TypeString,

website/docs/r/compute_network.html.markdown

@@ -96,8 +96,11 @@ The following arguments are supported:
 
 * `mtu` -
   (Optional)
-  Maximum Transmission Unit in bytes. The minimum value for this field is 1460
-  and the maximum value is 1500 bytes.
+  Maximum Transmission Unit in bytes. The default value is 1460 bytes. 
+  The minimum value for this field is 1300 and the maximum value is 8896 bytes (jumbo frames).
+  Note that packets larger than 1500 bytes (standard Ethernet) can be subject to TCP-MSS clamping or dropped
+  with an ICMP `Fragmentation-Needed` message if the packets are routed to the Internet or other VPCs 
+  with varying MTUs.
 
 * `enable_ula_internal_ipv6` -
   (Optional)