我正在按照教程评估 Istio 作为我的 K8s 集群的服务网格，但由于某种原因，我无法制作使用几个服务正常工作的简单示例：
https://istio.io/docs/tasks/integrating-services-into-istio.html
如果我尝试从服务一调用服务二，我会收到此错误：
# kubectl exec -ti ${CLIENT} -- curl -v service-two:80
Defaulting container name to app.
Use 'kubectl describe pod/service-one-714088666-73fkp' to see all of the containers in this pod.
* Rebuilt URL to: service-two:80/
* Trying 10.102.51.89...
* connect to 10.102.51.89 port 80 failed: Connection refused
* Failed to connect to service-two port 80: Connection refused
* Closing connection 0
curl: (7) Failed to connect to service-two port 80: Connection refused
但是，如果我尝试从集群中的另一个服务连接到 service-2，即使在不同的命名空间中，它也可以工作：
# kubectl exec -ti redis-4054078334-mj287 -n redis -- curl -v service-two.default:80
* Rebuilt URL to: service-two.default:80/
* Hostname was NOT found in DNS cache
* Trying 10.102.51.89...
* Connected to service-two.default (10.102.51.89) port 80 (#0)
> GET / HTTP/1.1
> User-Agent: curl/7.38.0
> Host: service-two.default
> Accept: */*
>
< HTTP/1.1 200 OK
* Server envoy is not blacklisted
< server: envoy
< date: Sat, 19 Aug 2017 14:43:01 GMT
< content-type: text/plain
< x-envoy-upstream-service-time: 2
< transfer-encoding: chunked
<
CLIENT VALUES:
client_address=127.0.0.1
command=GET
real path=/
query=nil
request_version=1.1
request_uri=http://service-two.default:8080/
SERVER VALUES:
server_version=nginx: 1.10.0 - lua: 10001
HEADERS RECEIVED:
accept=*/*
content-length=0
host=service-two.default
user-agent=curl/7.38.0
x-b3-sampled=1
x-b3-spanid=00000caf6e052e86
x-b3-traceid=00000caf6e052e86
x-envoy-expected-rq-timeout-ms=15000
x-forwarded-proto=http
x-ot-span-context=00000caf6e052e86;00000caf6e052e86;0000000000000000;cs
x-request-id=1290973c-7bca-95d2-8fa8-80917bb404ad
BODY:
* Connection #0 to host service-two.default left intact
-no body in request-
为什么我得到这种意外行为的任何原因或解释？
谢谢。