Let's take our example from the [overview](https://docs.traefik.io/#overview) again:
> Imagine that you have deployed a bunch of microservices on your infrastructure. You probably used a service registry (like etcd or consul) and/or an orchestrator (swarm, Mesos/Marathon) to manage all these services.
> If you want your users to access some of your microservices from the Internet, you will have to use a reverse proxy and configure it using virtual hosts or prefix paths:
> - domain `api.domain.com` will point the microservice `api` in your private network
> - path `domain.com/web` will point the microservice `web` in your private network
> - domain `backoffice.domain.com` will point the microservices `backoffice` in your private network, load-balancing between your multiple instances
> 
Let's zoom on Træfɪk and have an overview of its internal architecture:
- Incoming requests end on [entrypoints](#entrypoints), as the name suggests, they are the network entry points into Træfɪk (listening port, SSL, traffic redirection...).
Routes are created using requests fields (`Host`, `Path`, `Headers`...) and can match or not a request.
- The [frontend](#frontends) will then send the request to a [backend](#backends). A backend can be composed by one or more [servers](#servers), and by a load-balancing strategy.
- Finally, the [server](#servers) will forward the request to the corresponding microservice in the private network.
## Entrypoints
Entrypoints are the network entry points into Træfɪk.
-`Headers: Content-Type, application/json`: Headers adds a matcher for request header values. It accepts a sequence of key/value pairs to be matched.
-`HeadersRegexp: Content-Type, application/(text|json)`: Regular expressions can be used with headers as well. It accepts a sequence of key/value pairs, where the value has regex support.
-`Host: traefik.io, www.traefik.io`: Match request host with given host list.
-`HostRegexp: traefik.io, {subdomain:[a-z]+}.traefik.io`: Adds a matcher for the URL hosts. It accepts templates with zero or more URL variables enclosed by `{}`. Variables can define an optional regexp pattern to be matched.
-`Path: /products/, /articles/{category}/{id:[0-9]+}`: Path adds a matcher for the URL paths. It accepts templates with zero or more URL variables enclosed by `{}`.
In order to use path regular expressions, you must declare an arbitrarily named variable followed by the colon-separated regular expression, all enclosed in curly braces. Any pattern supported by [Go's regexp package](https://golang.org/pkg/regexp/) may be used. Example: `/posts/{id:[0-9]+}`.
(Note that the variable has no special meaning; however, it is required by gorilla/mux which embeds the regular expression and defines the syntax.)
-`frontend1` will forward the traffic to the `backend2` if the rule `Host:test.localhost,test2.localhost` is matched
-`frontend2` will forward the traffic to the `backend1` if the rule `Host:localhost,{subdomain:[a-z]+}.localhost` is matched (forwarding client `Host` header to the backend)
-`frontend3` will forward the traffic to the `backend2` if the rules `Host:test3.localhost`**AND**`Path:/test` are matched
-`drr`: Dynamic Round Robin: increases weights on servers that perform better than others. It also rolls back to original weights if the servers have changed.
A circuit breaker can also be applied to a backend, preventing high loads on failing servers.
Initial state is Standby. CB observes the statistics and does not modify the request.
A health check can be configured in order to remove a backend from LB rotation
as long as it keeps returning HTTP status codes other than 200 OK to HTTP GET
requests periodically carried out by Traefik. The check is defined by a path
appended to the backend URL and an interval (given in a format understood by [time.ParseDuration](https://golang.org/pkg/time/#ParseDuration)) specifying how
often the health check should be executed (the default being 30 seconds). Each
backend must respond to the health check within 5 seconds.
A recovering backend returning 200 OK responses again is being returned to the
Here is an example of backends and servers definition:
```toml
[backends]
[backends.backend1]
[backends.backend1.circuitbreaker]
expression = "NetworkErrorRatio() > 0.5"
[backends.backend1.servers.server1]
url = "http://172.17.0.2:80"
weight = 10
[backends.backend1.servers.server2]
url = "http://172.17.0.3:80"
weight = 1
[backends.backend2]
[backends.backend2.LoadBalancer]
method = "drr"
[backends.backend2.servers.server1]
url = "http://172.17.0.4:80"
weight = 1
[backends.backend2.servers.server2]
url = "http://172.17.0.5:80"
weight = 2
```
- Two backends are defined: `backend1` and `backend2`
-`backend1` will forward the traffic to two servers: `http://172.17.0.2:80"` with weight `10` and `http://172.17.0.3:80` with weight `1` using default `wrr` load-balancing strategy.
-`backend2` will forward the traffic to two servers: `http://172.17.0.4:80"` with weight `1` and `http://172.17.0.5:80` with weight `2` using `drr` load-balancing strategy.
- a circuit breaker is added on `backend1` using the expression `NetworkErrorRatio() > 0.5`: watch error ratio over 10 second sliding window
List of Træfɪk availablecommands with description :
-`version` : Printversion
-`storeconfig` : Store the static traefik configuration into a Key-value stores.Please refer to the [Store Træfɪk configuration](/user-guide/kv-config/#store-trfk-configuration) section to get documentation on it.
