HTTP2 connection coalescing and concurrent multiplexing for virtual server load balancing

HTTP2 connection coalescing and concurrent multiplexing allows multiple HTTP2 requests to share the same TLS connection when the destination IP is the same.

To configure the load balanced virtual server:

config firewall vip
    edit <name>
        set type server-load-balance 
        set server-type {http | https}
        set http-multiplex {enable | disable}
        set http-multiplex-ttl <integer>
        set http-multiplex-max-request <integer>
        set http-supported-max-version {http1 | http2}
    next
end

http-multiplex {enable | disable}	Enable/disable HTTP multiplexing.
http-multiplex-ttl <integer>	Set the time-to-live for idle connections to servers (in seconds, 0 - 2147483647, default = 15).
http-multiplex-max-request <integer>	Set the maximum number of requests that the multiplex server can handle before disconnecting (0 - 2147483647, default = 0).
http-supported-max-version {http1 | http2}	Set the maximum supported HTTP version: http1: support HTTP 1.1 and HTTP1. http2: support HTTP2, HTTP 1.1, and HTTP1 (default).

Example

In this example, multiple clients submit requests in HTTP2. The requests hit the VIP address, and then FortiProxy opens a session between itself (172.16.200.6) and the server (172.16.200.99). The coalescing occurs in this session as the multiple streams share the same TLS session to connect to the same destination server.

To configure connection coalescing and concurrent multiplexing with virtual server load balancing:

1. Configure the virtual server:

   config firewall vip
       edit "vip-test"
           set type server-load-balance
           set extip 10.1.100.222
           set extintf "port2"
           set server-type https
           set extport 443
           config realservers
               edit 1
                   set ip 172.16.200.99
                   set port 443
               next
           end
           set http-multiplex enable
           set ssl-mode full
           set ssl-certificate "Fortinet_SSL"
       next
   end

2. Configure the firewall policy:

   config firewall policy
       edit 1
           set srcintf "port2"
           set dstintf "port3"
           set action accept
           set srcaddr "all"
           set dstaddr "vip-test"
           set schedule "always"
           set service "ALL"
           set utm-status enable
           set inspection-mode proxy
           set ssl-ssh-profile "deep-inspection-clone"
           set av-profile "av"
           set logtraffic all
           set nat enable
       next
   end
   

3. Get the clients to access the VIP address (10.1.100.222). The FortiProxy shares the first TLS connection with second TLS connection.

4. Verify the sniffer packet capture on the FortiProxy server side. There is one client hello.

   

5. Disable HTTP multiplexing:

   config firewall vip
       edit "vip-test"
           config realservers
               edit 1
                   set type ip
                   set ip 172.16.200.99
                   set port 443
               next
           end
           set http-multiplex disable
       next
   end

6. Verify the sniffer packet capture. This time, the FortiProxy does reuse the TLS connection, so there are two client hellos sent to the real server.