consul rtt very different from icmp rtt

Hello!

#### Overview of the Issue

I just wonder why i have a big difference:
node1 -> node2 icmp rtt 0.100ms
node1 -> node2 consul rtt 0.460ms

### Consul info for both Client and Server

I have Consul v1.6.2 on all servers, about 50 nodes.

```
agent:
check_monitors = 1
check_ttls = 0
checks = 7
services = 7
build:
prerelease =
revision = 1200f25e
version = 1.6.2
consul:
acl = disabled
known_servers = 5
server = false
runtime:
arch = amd64
cpu_count = 12
goroutines = 59
max_procs = 12
os = linux
version = go1.12.13
serf_lan:
coordinate_resets = 0
encrypted = true
event_queue = 0
event_time = 589
failed = 0
health_score = 0
intent_queue = 0
left = 0
member_time = 2323
members = 49
query_queue = 0
query_time = 1

```

### Operating system and Environment details

RedHat7, x86-64. All nodes in one network in virtualization system.

How i can generate a more precise network tree?