Merge pull request #5571 from Lion-Wei/patch-16

add proxy-mode:ipvs in service.md

docs/concepts/services-networking/service.md

@@ -207,6 +207,36 @@ having working [readiness probes](/docs/tasks/configure-pod-container/configure-
 
 ![Services overview diagram for iptables proxy](/images/docs/services-iptables-overview.svg)
 
+### Proxy-mode: ipvs[alpha]
+
+**Warning:** This is an alpha feature and not recommended for production clusters yet.
+
+In this mode, kube-proxy watches Kubernetes `services` and `endpoints`,
+call `netlink` interface create ipvs rules accordingly and sync ipvs rules with Kubernetes
+`services` and `endpoints`  periodically, to make sure ipvs status is
+consistent with the expectation. When access the `service`, traffic will
+be redirect to one of the backend `pod`.
+
+Similar to iptables, Ipvs is based on netfilter hook function, but use hash
+table as the underlying data structure and work in the kernal state.
+That means ipvs redirects traffic can be much faster, and have much
+better performance when sync proxy rules. Furthermore, ipvs provides more
+options for load balancing algorithm, such as:
+
+- rr: round-robin
+- lc: least connection
+- dh: destination hashing
+- sh: source hashing
+- sed: shortest expected delay
+- nq: never queue
+
+**Note:** ipvs mode assumed IPVS kernel modules are installed on the node
+before running kube-proxy. When kube-proxy starts, if proxy mode is ipvs,
+kube-proxy would validate if IPVS modules are installed on the node, if
+it's not installed kube-proxy will fall back to iptables proxy mode.
+
+![Services overview diagram for ipvs proxy](/images/docs/services-ipvs-overview.svg)
+
 ## Multi-Port Services
 
 Many `Services` need to expose more than one port.  For this case, Kubernetes