Calico ipipMode Always VS. Never

In ipipMode: Always, All traffics to pod CIDR (10.169.0.0/16) goes though tunl0 interface

$ calicoctl get ipPool default-ipv4-ippool -o json| jq -r .spec
{
  "cidr": "10.169.0.0/16",
  "vxlanMode": "Never",
  "ipipMode": "Always",
  "natOutgoing": true,
  "blockSize": 26,
  "nodeSelector": "all()",
  "allowedUses": [
    "Workload",
    "Tunnel"
  ]
}
$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.0.1     0.0.0.0         UG    100    0        0 eth0
10.169.119.128  192.168.0.171   255.255.255.192 UG    0      0        0 tunl0
10.169.152.192  0.0.0.0         255.255.255.192 U     0      0        0 *
10.169.198.128  192.168.0.200   255.255.255.192 UG    0      0        0 tunl0
10.169.198.192  192.168.0.200   255.255.255.192 UG    0      0        0 tunl0
192.168.0.0     0.0.0.0         255.255.255.0   U     100    0        0 eth0
$

compare to ipipMode: Never , traffics to destination pod directly goes though eth0 interface

$ calicoctl apply -f ipPool-Never.yaml 
Successfully applied 1 'IPPool' resource(s)
$ 
 $ calicoctl get ipPool default-ipv4-ippool -o json| jq -r .spec
{
  "cidr": "10.169.0.0/16",
  "vxlanMode": "Never",
  "ipipMode": "Never",
  "natOutgoing": true,
  "blockSize": 26,
  "nodeSelector": "all()",
  "allowedUses": [
    "Workload",
    "Tunnel"
  ]
}
$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.0.1     0.0.0.0         UG    100    0        0 eth0
10.169.119.128  192.168.0.171   255.255.255.192 UG    0      0        0 eth0
10.169.152.192  0.0.0.0         255.255.255.192 U     0      0        0 *
10.169.198.128  192.168.0.200   255.255.255.192 UG    0      0        0 eth0
192.168.0.0     0.0.0.0         255.255.255.0   U     100    0        0 eth0
$ 

ipipMode: Never or CrossSubnet no need tunl0 and may have batter performance than ipipMode: Always

$ cat ipPool-Never.yaml 
apiVersion: projectcalico.org/v3
kind: IPPool
metadata:
  name: default-ipv4-ippool
spec:
  allowedUses:
  - Workload
  - Tunnel
  blockSize: 26
  cidr: 10.169.0.0/16
  ipipMode: Never
  natOutgoing: true
  nodeSelector: all()
  vxlanMode: Never

refer: https://projectcalico.docs.tigera.io/reference/resources/ippool