This section discusses about HTTP/2 support in Avi Load Balancer. HTTP/2 (originally named HTTP/2.0) is the latest version of HTTP and developed over HTTP 1.1. HTTP/2 is a binary protocol, while HTTP 1.1 is a text protocol.
The following are the benefits of HTTP/2 over HTTP/1.1:
Request and Response Multiplexing - With HTTP/1.1,for multiple parallel requests, multiple TCP connections are opened. With HTTP/2, multiple requests can be broken into frames that can be interleaved; the remote end is capable of reassembling them. Multiple connections can still be opened, but the number of connections is not as many as in HTTP/1.1.
Server Push - It allows a server to send multiple resources in response to a client request without the client explicitly sending a request for each of these resources. This reduces latency otherwise introduced by waiting for each request to serve the resource. In HTTP/1.1, applications try to work around this by inlining the resource. HTTP/2 enables the client to cache the resource, reuse it across pages, and use multiplexing along with other resources.
Flow control - HTTP/2 provides flow control at the application layer level by not allowing either end to overwhelm the other side, by using window sizes.
Header Compression - In HTTP/1.1, each header in the request is sent as text. In HTTP/2, the header compresses request and response header metadata using the HPACK compression format, reducing the transmitted header size.
Stream Prioritization - Since the HTTP messages are sent as frames and the frames from different streams can be interleaved, HTTP/2 can specify priorities for streams. That is, all frames received can be prioritized based on their stream priorities.
Avi Load Balancer supports HTTP/2 server push.
Use Cases
Workaround techniques used for HTTP 1.1 to make browsers compatible with HTTP/2, are no longer required.
All browsers that use HTTP/2 can be deployed on Avi Load Balancer.
Support for the application using reverse proxy for gRPC.
Supported methods and modes for HTTP/2 on Avi Load Balancer
HTTP over TLS or HTTP over SSL - The Avi Load Balancer supports HTTP over TLS, or HTTP over SSL method for all HTTP/2 requests. This method uses TLS version 1.2 or later.
All settings and options available for HTTP Setting are also available for HTTP/2-enabled virtual services. HTTP features like HTTP policy, DataScripts, the HTTP timeout setting, and more are also supported for HTTP/2 requests.
HTTP/2 Support for Virtual Service, Pool, and Pool Groups
HTTP/2 is supported for front-end and back-end (server-side) connections. The following enhancements are available for HTTP/2:
For front-end traffic, HTTP/2 is supported on both non-SSL and SSL enabled ports.
For back-end traffic, HTTP/2 is enabled at the pool level.
Enabling HTTP/2 on Virtual Service and Pools
The HTTP/2 configuration option is not available through the application profile. It can be accessed through virtual service configuration.
The following configuration changes support HTTP/2 on the front-end and the back-end:
The http2_enabled flag is deprecated from the application profile.
The enable_http2 flag is available for the virtual service.
The enable_http2 flag is available for the pool and pool group level to indicate that all the servers configured under this pool are HTTP/2.0 servers.
Configuring HTTP/2 using Avi Load Balancer
To configure HTTP2 for the virtual service, follow the steps below:
Navigate to .
Edit the existing virtual service or create a new one.
Select the check box for HTTP2 available under .
HTTP2 can be enabled for SSL and non-SSL ports as required.
To configure HTTP2 for the pools and the pool groups associated with the virtual service, follow the steps below:
Navigate to and click Create Pool or use the existing one. Select the Enable HTTP2 check box available under Servers as shown below:
2. For pool groups, navigate to and click Create Pool Group or use the existing one. For enabling HTTP2, select the check box for Enable HTTP2 available under Pool Servers as shown below:
Configuring HTTP/2 using Avi Load Balancer UI
Navigate to , use the existing virtual service or create a new one. Select HTTP2 available under . HTTP2 can be enabled for SSL and non-SSL ports as required.
Enable HTTP2 for the pools and the pool groups associated with the virtual service. Navigate to and click Create Pool or use the existing one. Select the Enable HTTP2 option available under Servers.
For enabling HTTP2 for pool groups, select Enable HTTP2 available under Members.
Configuring HTTP/2 using Avi Load Balancer CLI
Use the enable_http2 flag from the configure virtual service mode.
Configuring Virtual Service
[admin:controller]: > configure virtualservice http2_vs [admin:controller]: virtualservice> services index 1 [admin:controller]: virtualservice:services> enable_http2
Similarly, use the enable_http2 flag for the associated pool and pool groups for the virtual service.
Configuring Pool
[admin:controller]: > configure pool v2-pool [admin:controller]: pool> enable_http2
Configuring Pool group
Use the following steps to enable HTTP/2 for a pool group.
[admin:controller]: > configure poolgroup v2-pg [admin:controller]: poolgroup> enable_http2
Enabling HTTP/2 for Existing Pool Groups: To enable HTTP/2 for an existing pool group:
Remove all pool members from the pool groups.
Configure enable_http2 for all the pools using the steps mentioned above.
Configure enable_http2 for the pool group.
Add all the pools to pool group.
Checking Status
The show virtualservice <virtual service name> command exhibits the flag value set as true, as shown in the following code output:
[admin:controller]: > show virtualservice http2-vs +------------------------------------+-----------------------------------------------------+ | Field | Value | +------------------------------------+-----------------------------------------------------+ | uuid | virtualservice-2d67f7ed-eeee-4b81-af01-78ded84f4352 | | name | http2-vs | | enabled | True | | services[1] | | | port | 80 | | enable_ssl | False | | port_range_end | 80 | | enable_http2 | True |<---- | services[2] | | | port | 443 | | enable_ssl | True | | port_range_end | 443 |<---- | eable_http2 | True | | application_profile_ref | applicationprofile-22 | | network_profile_ref | System-TCP-Proxy | | pool_ref | v2-pool | | se_group_ref | Default-Group | | http_policies[1] | | | index | 11 | | http_policy_set_ref | http_request_policy_1 | +------------------------------------+-----------------------------------------------------+
[admin:controller]: > show pool v2-pool +---------------------------------------+------------------------------------------------+ | Field | Value | +---------------------------------------+------------------------------------------------+ | uuid | pool-5f38c27f-ff10-48e1-88e2-a9a2b39ad198 | | name | v2-pool | | default_server_port | 80 | | graceful_disable_timeout | 1 min | | connection_ramp_duration | 10 min | | max_concurrent_connections_per_server | 0 | | servers[1] | | | ip | 10.90.103.72 | | port | 80 | | hostname | 10.90.103.72 | | enabled | True | | ratio | 1 | | verify_network | False | | resolve_server_by_dns | False | | static | False | | rewrite_host_header | False | | lb_algorithm | LB_ALGORITHM_LEAST_CONNECTIONS | | lb_algorithm_hash | LB_ALGORITHM_CONSISTENT_HASH_SOURCE_IP_ADDRESS | | inline_health_monitor | True | | use_service_port | False | | capacity_estimation | False | | capacity_estimation_ttfb_thresh | 0 milliseconds | | vrf_ref | global | | fewest_tasks_feedback_delay | 10 sec | | enabled | True | | request_queue_enabled | False | | request_queue_depth | 128 | | host_check_enabled | False | | sni_enabled | True | | rewrite_host_header_to_sni | False | | rewrite_host_header_to_server_name | False | | lb_algorithm_core_nonaffinity | 2 | | lookup_server_by_name | False | | analytics_profile_ref | System-Analytics-Profile | | tenant_ref | admin | | cloud_ref | Default-Cloud | | server_timeout | 0 milliseconds | | delete_server_on_dns_refresh | True | | enable_http2 | True | <----- +---------------------------------------+------------------------------------------------+
Limitations
Caching is not supported for HTTP/2 pool.
HTTP/2 Connection multiplexing on upstream is not supported.
HTTP/2 health monitor support is not available. If the back-end server only supports HTTP/2, HTTP(S) health monitor will not work for this pool. Only TCP or PING health monitor must be configured for this pool.
If the back-end server is SSL-enabled and supports both HTTP/1 and HTTP/2, HTTPS health monitor must be configured with its own attribute.
For non-SSL enabled port, HTTP/1.1 to HTTP/2.0 upgrade is not supported.
The client must be aware that the non-SSL port can only support HTTP/2.
The back-end pool assumes that servers listening on the configured port only support HTTP/2 and will not send an HTTP1.1 to HTTP/2.0 upgrade.
For the pool group, the HTTP version must be matched between the pool group and all the associated pools.
HTTP/1.1 chunked transfer-encoding mechanism on one side (the front-end) and HTTP/2 chunked mechanism on the other side (back-end) is not supported together. If chunking is present. That is, if stream mode or partial buffer mode is required with chunk on one side and V2 chunk on the another side, this method is not supported.
Upgrade
If HTTP/2 is enabled in the application profile for a virtual service listening on port 80 and 443, after an upgrade, the HTTP/2 will be automatically enabled on the virtual service on port 443. HTTP/2 will not be enabled on port 80 which is non-SSL enabled port.
Additional Configuration Options for HTTP/2 Profile
The HTTP/2 configuration fields have been moved to a sub-field under http_profile called http2_profile. The following fields have been added to the http2_profile:
max_http2_requests_per_connection: This value controls the maximum number of requests that can be sent over a client-side HTTP/2 connection. If the value is set to 0, an unlimited number of requests can be sent over an HTTP/2 client-side connection.
max_http2_header_field: This field controls the maximum size (in bytes) of the compressed request header field. The limit applies equally to both name and value of the request header in the range 1-8192 bytes. The default value is 4096 bytes.
http2_initial_window_size: This field controls the window size of the initial flow control in HTTP/2 streams. The value for this field is in the range 64 -32768 KB. The default value is 64 KB.
max_http2_control_frames_per_connection: This field controls the number of control frames that client can send over an HTTP/2 connection. The value for this field ranges from 0-10000, and the default value is 1000. Set the value to zero value for allowing unlimited number of control frames to be sent on a client-side HTTP/2 connection.max_http2_queued_frames_to_client_per_connection: This field controls the number of frames that can be queued waiting to be sent over a client-side HTTP/2 connection at any given time. The value for this field ranges from 0-10000, and the default value is 1000. The zero value for this parameter indicates that unlimited frames can be queued on a client-side HTTP/2 connection.max_http2_empty_data_frames_per_connection: This field controls the number of empty data frames that the client can send over an HTTP/2 connection. The value for this field ranges from 0-10000, and the default value is 1000. The zero value for this parameter indicates that unlimited empty data frames can be sent over a client-side HTTP/2 connection.max_http2_concurrent_streams_per_connection: This field is to configure the maximum number of concurrent streams over a client-side HTTP/2 connection. The value for this field ranges from 1-256, and the default value is 128.
The following CLI snippets exhibit configuration samples for the options mentioned above. Login to the Avi Load Balancer CLI. Use the applicationprofile mode and the http2_profile option to change the values of the parameters mentioned above.
[admin:controller]: > configure applicationprofile ap-1 Updating an existing object. Currently, the object is: +------------------------------------------------------+---------------------------------------------------------+ | Field | Value | +------------------------------------------------------+---------------------------------------------------------+ | uuid | applicationprofile-1d264f41-d19c-445e-a4df-740dca5957f0 | | name | ap-1 | | type | APPLICATION_PROFILE_TYPE_HTTP | | http_profile | | | connection_multiplexing_enabled | True | | xff_enabled | True | | xff_alternate_name | X-Forwarded-For | | hsts_enabled | False | | hsts_max_age | 365 | | secure_cookie_enabled | False | | httponly_enabled | False | | http_to_https | False | | server_side_redirect_to_https | False | | x_forwarded_proto_enabled | False | | post_accept_timeout | 30000 milliseconds | | client_header_timeout | 10000 milliseconds | | client_body_timeout | 30000 milliseconds | | keepalive_timeout | 30000 milliseconds | | client_max_header_size | 12 kb | | client_max_request_size | 48 kb | | client_max_body_size | 0 kb | | max_rps_unknown_uri | 0 | | max_rps_cip | 0 | | max_rps_uri | 0 | | max_rps_cip_uri | 0 | | ssl_client_certificate_mode | SSL_CLIENT_CERTIFICATE_NONE | | websockets_enabled | True | | max_rps_unknown_cip | 0 | | max_bad_rps_cip | 0 | | max_bad_rps_uri | 0 | | max_bad_rps_cip_uri | 0 | | keepalive_header | False | | use_app_keepalive_timeout | False | | allow_dots_in_header_name | False | | disable_keepalive_posts_msie6 | True | | enable_request_body_buffering | False | | enable_fire_and_forget | False | | max_response_headers_size | 48 kb | | respond_with_100_continue | True | | hsts_subdomains_enabled | True | | enable_request_body_metrics | False | | fwd_close_hdr_for_bound_connections | True | | max_keepalive_requests | 100 | | disable_sni_hostname_check | False | | reset_conn_http_on_ssl_port | False | | http_upstream_buffer_size | 0 kb | | enable_chunk_merge | True | | http2_profile | | | max_http2_control_frames_per_connection | 1000 | | max_http2_queued_frames_to_client_per_connection | 1000 | | max_http2_empty_data_frames_per_connection | 1000 | | max_http2_concurrent_streams_per_connection | 128 | | max_http2_requests_per_connection | 1000 | | max_http2_header_field_size | 4096 bytes | | http2_initial_window_size | 64 kb | | preserve_client_ip | False | | preserve_client_port | False | | preserve_dest_ip_port | False | | tenant_ref | admin | +------------------------------------------------------+---------------------------------------------------------+ [admin:controller]: applicationprofile> http_profile [admin:controller]: applicationprofile:http_profile> http2_profile [admin:controller]: applicationprofile:http_profile:http2_profile> max_http2_control_frames_per_connection 2000 Overwriting the previously entered value for max_http2_control_frames_per_connection [admin:controller]: applicationprofile:http_profile:http2_profile> max_http2_queued_frames_per_connection 2000 No command or arguments found in 'max_http2_queued_frames_per_connection 2000'. [admin:controller]: applicationprofile:http_profile:http2_profile> max_http2_queued_frames_to_client_per_connection 2000 Overwriting the previously entered value for max_http2_queued_frames_to_client_per_connection [admin:controller]: applicationprofile:http_profile:http2_profile> max_http2_concurrent_streams_per_connection 256 Overwriting the previously entered value for max_http2_concurrent_streams_per_connection [admin:controller]: applicationprofile:http_profile:http2_profile> max_http2_requests_per_connection 2500 Overwriting the previously entered value for max_http2_requests_per_connection [admin:controller]: applicationprofile:http_profile:http2_profile> http2_initial_window_size 256 Overwriting the previously entered value for http2_initial_window_size [admin:controller]: applicationprofile:http_profile:http2_profile> max_http2_header_field_size 8192 Overwriting the previously entered value for max_http2_header_field_size [admin:controller]: applicationprofile:http_profile:http2_profile> save [admin:controller]: applicationprofile:http_profile> save [admin:controller]: applicationprofile> save +------------------------------------------------------+---------------------------------------------------------+ | Field | Value | +------------------------------------------------------+---------------------------------------------------------+ | uuid | applicationprofile-1d264f41-d19c-445e-a4df-740dca5957f0 | | name | ap-1 | | type | APPLICATION_PROFILE_TYPE_HTTP | | http_profile | | | connection_multiplexing_enabled | True | | xff_enabled | True | | xff_alternate_name | X-Forwarded-For | | hsts_enabled | False | | hsts_max_age | 365 | | secure_cookie_enabled | False | | httponly_enabled | False | | http_to_https | False | | server_side_redirect_to_https | False | | x_forwarded_proto_enabled | False | | post_accept_timeout | 30000 milliseconds | | client_header_timeout | 10000 milliseconds | | client_body_timeout | 30000 milliseconds | | keepalive_timeout | 30000 milliseconds | | client_max_header_size | 12 kb | | client_max_request_size | 48 kb | | client_max_body_size | 0 kb | | max_rps_unknown_uri | 0 | | max_rps_cip | 0 | | max_rps_uri | 0 | | max_rps_cip_uri | 0 | | ssl_client_certificate_mode | SSL_CLIENT_CERTIFICATE_NONE | | websockets_enabled | True | | max_rps_unknown_cip | 0 | | max_bad_rps_cip | 0 | | max_bad_rps_uri | 0 | | max_bad_rps_cip_uri | 0 | | keepalive_header | False | | use_app_keepalive_timeout | False | | allow_dots_in_header_name | False | | disable_keepalive_posts_msie6 | True | | enable_request_body_buffering | False | | enable_fire_and_forget | False | | max_response_headers_size | 48 kb | | respond_with_100_continue | True | | hsts_subdomains_enabled | True | | enable_request_body_metrics | False | | fwd_close_hdr_for_bound_connections | True | | max_keepalive_requests | 100 | | disable_sni_hostname_check | False | | reset_conn_http_on_ssl_port | False | | http_upstream_buffer_size | 0 kb | | enable_chunk_merge | True | | http2_profile | | | max_http2_control_frames_per_connection | 2000 | | max_http2_queued_frames_to_client_per_connection | 2000 | | max_http2_empty_data_frames_per_connection | 1000 | | max_http2_concurrent_streams_per_connection | 256 | | max_http2_requests_per_connection | 2500 | | max_http2_header_field_size | 8192 bytes | | http2_initial_window_size | 256 kb | | preserve_client_ip | False | | preserve_client_port | False | | preserve_dest_ip_port | False | | tenant_ref | admin | +------------------------------------------------------+---------------------------------------------------------+ [admin:controller]: >
[admin:controller]: > show applicationprofile ap-1 +------------------------------------------------------+---------------------------------------------------------+ | Field | Value | +------------------------------------------------------+---------------------------------------------------------+ | uuid | applicationprofile-1d264f41-d19c-445e-a4df-740dca5957f0 | | name | ap-1 | | type | APPLICATION_PROFILE_TYPE_HTTP | | http_profile | | | connection_multiplexing_enabled | True | | xff_enabled | True | | xff_alternate_name | X-Forwarded-For | | hsts_enabled | False | | hsts_max_age | 365 | | secure_cookie_enabled | False | | httponly_enabled | False | | http_to_https | False | | server_side_redirect_to_https | False | | x_forwarded_proto_enabled | False | | post_accept_timeout | 30000 milliseconds | | client_header_timeout | 10000 milliseconds | | client_body_timeout | 30000 milliseconds | | keepalive_timeout | 30000 milliseconds | | client_max_header_size | 12 kb | | client_max_request_size | 48 kb | | client_max_body_size | 0 kb | | max_rps_unknown_uri | 0 | | max_rps_cip | 0 | | max_rps_uri | 0 | | max_rps_cip_uri | 0 | | ssl_client_certificate_mode | SSL_CLIENT_CERTIFICATE_NONE | | websockets_enabled | True | | max_rps_unknown_cip | 0 | | max_bad_rps_cip | 0 | | max_bad_rps_uri | 0 | | max_bad_rps_cip_uri | 0 | | keepalive_header | False | | use_app_keepalive_timeout | False | | allow_dots_in_header_name | False | | disable_keepalive_posts_msie6 | True | | enable_request_body_buffering | False | | enable_fire_and_forget | False | | max_response_headers_size | 48 kb | | respond_with_100_continue | True | | hsts_subdomains_enabled | True | | enable_request_body_metrics | False | | fwd_close_hdr_for_bound_connections | True | | max_keepalive_requests | 100 | | disable_sni_hostname_check | False | | reset_conn_http_on_ssl_port | False | | http_upstream_buffer_size | 0 kb | | enable_chunk_merge | True | | http2_profile | | | max_http2_control_frames_per_connection | 1000 | | max_http2_queued_frames_to_client_per_connection | 1000 | | max_http2_empty_data_frames_per_connection | 1000 | | max_http2_concurrent_streams_per_connection | 128 | | max_http2_requests_per_connection | 1000 | | max_http2_header_field_size | 4096 bytes | | http2_initial_window_size | 64 kb | | preserve_client_ip | False | | preserve_client_port | False | | preserve_dest_ip_port | False | | tenant_ref | admin | +------------------------------------------------------+---------------------------------------------------------+
Logs
Logs can be checked using one of the following modes:
Using Avi Load Balancer UI
Using Avi Load Balancer CLI
Checking Logs Using UI
The application logs of Avi Load Balancer display HTTP/2.0 as the HTTP version in the request. Navigate to , select the desired virtual service, and navigate to Logs tab to check logs.
Errors related to HTTP/2 requests and response can be checked under Significant logs.
Checking Logs Using CLI
The following are counters available for the HTTP/2 feature, that can be used during troubleshooting.
Request handled error
Response codes (2xx, 3xx, 4xx, and 5xx)
Protocol errors
Flow-control error
Frame size errors
Compression errors
Refused Stream errors
Use the show virtualservice <virtual service name> detail command to check for available counters for the HTTP/2 method.
[admin:controller]: > show virtualservice <virtual service name> detail | cache_bytes | 0 | | http2_requests_handled | 2 | | http2_response_2xx | 2 | | http2_response_3xx | 0 | | http2_response_4xx | 0 | | http2_response_5xx | 0 | | http2_protocol_errors | 0 | | http2_flow_control_errors | 0 | | http2_frame_size_errors | 0 | | http2_compression_errors | 0 | | http2_refused_stream_errors | 0 | | http2_enhance_your_calm | 0 | | http2_miscellaneous_errors | 0
Use the show pool <pool name> detail command to check HTTP/2-related errors in pool status.
[admin:controller]: > show pool v2-pool detail | grep http2 | http2_protocol_header_errors | 0 | | http2_protocol_other_errors | 0 | | http2_flow_control_errors | 0 | | http2_frame_size_errors | 0 | | http2_compression_errors | 0 | | http2_refused_stream_errors | 0 | | http2_enhance_your_calm | 0 | | http2_misc_errors | 0 | [admin:controller]:
HPACK Dynamic Table
In addition to the static table, HPACK has a connection-level dynamic table starting at position 62 (after the static table) up to the maximum table size defined by the SETTINGS_HEADER_TABLE_SIZE value in the SETTINGS frame. The default is 4096 octets if not explicitly defined. When the maximum table size is reached, the oldest entry is evicted. To make this process easier, each entry is incremented when the table is written to.
The table entry position for a header is not static. It increments continually as new headers are added to the table in current and future requests. TCP guarantees this order, so in HTTP/2, the dynamic table is unique to each TCP connection.
For complete information on HPACK header types, see RFC7541.
The dynamic HPACK table is already supported on the client side. Starting with version 22.1.1, Avi Load Balancer has added server side support.
On the server side, when Avi Load Balancer tries to create an HTTP2 connection, it will check if the cache is enabled on the virtual service. If cached is enabled, it will turn off the dynamic hpack table by setting SETTINGS_HEADER_TABLE_SIZE value as zero in the SETTINGS frame. If the cache is not enabled, Avi Load Balancer will set SETTINGS_HEADER_TABLE_SIZE as 4k. SETTINGS_HEADER_TABLE_SIZE is not configurable.
