across multiple cores that share the same L2 cache  • We do ECMP (Equal Cost Multi Path)  in our edge routers for sharding traffic across the load balancers. lb lb lb lb router ip route 95.131.168.x/32 x.x.x.2 ip route 95.131.168.x/32 x.x.x.1 ip route 95.131.168.x/32 x.x.x.3 ip route 95.131.168.x/32 x.x.x.4
start, throttling, anti-DoS features, supervision, content switching, keep-alive, etc. • Very robust and reliable. • Designed to be a load balancer. • Offers high control over HTTP delivery and status: response codes, connections per frontend, queued request, etc.
connections. • Backend: Pool of servers. We define algorithm, configure healthy checks, etc. • Listen section: frontend+backend. Useful for TCP. • Connection != request: One connection can hold multiple requests (keep-alive). Only the first one is analyzed, logged and processed.
backend server. You can issue these cookies from the code and play with them. • Ideal for deploying code by stages, or caching locally user data. • If the server becomes unreachable the traffic will be directed to other server within the same pool.
servers (i.e.Varnish). Without this feature the cache pool will be inefficient. • The URLs are hashed and assigned to a server in the pool (using a modulo operation). A server will serve always the same object regardless of the load balancer that attends the request. • Adding/removing/losing servers to the pool is not harmful thanks to consistent hashing.
• Take decisions about which backend will attend the connection based on: • Layer 7 information (HTTP headers, methods, URI, version, status) • Layer4 information (source IP, destination IP, port) • Internal HAProxy information (amount of backend connections, active servers in the backend, etc) • Too much options for showing all on this presentation. 
• We deployed stunnel and it worked fine for a while. • Then we started to suffer contention when accepting new connections. • We are currently using stud  for terminating SSL in our load balancers.
SSL termination in your PCI compliant platform. • We transport client IP information into X-Forwarded-For headers in order to log users IPs because law enforcements. • We terminate SSL in the load balancer because balancing TCP (SSL) you can’t inform the backend about the client IP.
and TLS using OpenSSL. • Uses a process-per-core model. • Asynchronous I/O using libev. • Very little overhead per connection. • Designed for long-living connections. • Supports PROXY protocol. • Recently they added inter-process communication  .
transport connection information across multiple layers of NAT or TCP proxies. • Native support in stud. Patches available for stunnel4. • We use it for stud informing to HAProxy about the real IP of the client, converting this information to X-Forwarded-For header that we can read and store in our application.