{"id":118,"date":"2020-05-10T12:07:12","date_gmt":"2020-05-10T11:07:12","guid":{"rendered":"https:\/\/blog.thomarite.uk\/?p=118"},"modified":"2020-05-11T23:44:50","modified_gmt":"2020-05-11T22:44:50","slug":"tcp-congestion-control-and-recovery","status":"publish","type":"post","link":"https:\/\/blog.thomarite.uk\/index.php\/2020\/05\/10\/tcp-congestion-control-and-recovery\/","title":{"rendered":"TCP Congestion Control and Recovery"},"content":{"rendered":"\n

I have reading this new post from Cloudflare<\/a> about their congestion control implementations for QUIC<\/a>.<\/p>\n\n\n\n

Reading the article I wanted to check the TCP CCA (Congestion Control Algorithm) available in my laptop (Debian 1o Testing).<\/p>\n\n\n\n

So I searched a bit and found a couple of useful links like this<\/a>:<\/p>\n\n\n\n

For checking your current TCP CCA:<\/p>\n\n\n\n

# sysctl net.ipv4.tcp_congestion_control\nnet.ipv4.tcp_congestion_control = cubic\n\n$ cat \/proc\/sys\/net\/ipv4\/tcp_congestion_control\ncubic<\/pre>\n\n\n\n
For checking the available TCP CCAs:<\/p>\n\n\n\n
# sysctl net.ipv4.tcp_available_congestion_control\nnet.ipv4.tcp_available_congestion_control = reno cubic<\/pre>\n\n\n\n
As well, you can see via “ss” the CCA per connection:<\/p>\n\n\n\n
$ ss -ti\n...\ntcp   ESTAB      0       0                                     192.168.1.158:60238                     169.54.204.232:https       \n\t cubic wscale:7,7 rto:320 rtt:116.813\/2.428 ato:40 mss:1448 pmtu:1500 rcvmss:1448 advmss:1448 cwnd:10 bytes_sent:4366 bytes_acked:4367 bytes_received:7038 segs_out:98 segs_in:183 data_segs_out:91 data_segs_in:93 send 991.7Kbps lastsnd:1260 lastrcv:1260 lastack:1140 pacing_rate 2.0Mbps delivery_rate 102.2Kbps delivered:92 app_limited busy:10632ms rcv_space:14480 rcv_ssthresh:64088 minrtt:113.391\n...<\/pre>\n\n\n\n
If you want to change your TCP CCA, this is a good link<\/a>:<\/p>\n\n\n\n
Check the modules installed:<\/p>\n\n\n\n
$ ls -la \/lib\/modules\/$(uname -r)\/kernel\/net\/ipv4<\/pre>\n\n\n\n
Check the kernel config:<\/p>\n\n\n\n
$ grep TCP_CONG \/boot\/config-$(uname -r)\nCONFIG_TCP_CONG_ADVANCED=y\nCONFIG_TCP_CONG_BIC=m\nCONFIG_TCP_CONG_CUBIC=y\nCONFIG_TCP_CONG_WESTWOOD=m\nCONFIG_TCP_CONG_HTCP=m\nCONFIG_TCP_CONG_HSTCP=m\nCONFIG_TCP_CONG_HYBLA=m\nCONFIG_TCP_CONG_VEGAS=m\nCONFIG_TCP_CONG_NV=m\nCONFIG_TCP_CONG_SCALABLE=m\nCONFIG_TCP_CONG_LP=m\nCONFIG_TCP_CONG_VENO=m\nCONFIG_TCP_CONG_YEAH=m\nCONFIG_TCP_CONG_ILLINOIS=m\nCONFIG_TCP_CONG_DCTCP=m\nCONFIG_TCP_CONG_CDG=m\nCONFIG_TCP_CONG_BBR=m\nCONFIG_DEFAULT_TCP_CONG=\"cubic\"\n<\/pre>\n\n\n\n
We can see that “cubic” is the default TCP CCA and we have for example BBR available as a module.<\/p>\n\n\n\n
So let’s change to BBR (rfc<\/a>, github<\/a>, blog<\/a>) based on this link<\/a>:<\/p>\n\n\n\n
Check the kernel supports BBR:<\/p>\n\n\n\n
$ cat \/boot\/config-$(uname -r) | grep 'CONFIG_TCP_CONG_BBR'\nCONFIG_TCP_CONG_BBR=m\n$ cat \/boot\/config-$(uname -r) | grep 'CONFIG_NET_SCH_FQ'\nCONFIG_NET_SCH_FQ_CODEL=m\nCONFIG_NET_SCH_FQ=m<\/pre>\n\n\n\n
Enable TCP BBR:<\/p>\n\n\n\n
# vi \/etc\/sysctl.conf\nnet.core.default_qdisc=fq\nnet.ipv4.tcp_congestion_control=bbr<\/pre>\n\n\n\n
Apply the changes:<\/p>\n\n\n\n
# sysctl --system<\/pre>\n\n\n\n
And check:<\/p>\n\n\n\n
$ cat \/proc\/sys\/net\/ipv4\/tcp_congestion_control\nbbr<\/pre>\n\n\n\n
So we have moved from CUBIC to BBR. Let’s see how is the experience in the following days.<\/p>\n","protected":false},"excerpt":{"rendered":"
I have reading this new post from Cloudflare about their congestion control implementations for QUIC. Reading the article I wanted to check the TCP CCA (Congestion Control Algorithm) available in my laptop (Debian 1o Testing). So I searched a bit and found a couple of useful links like this: For checking your current TCP CCA: … Continue reading “TCP Congestion Control and Recovery”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,2],"tags":[],"class_list":["post-118","post","type-post","status-publish","format-standard","hentry","category-unix","category-networks"],"_links":{"self":[{"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/posts\/118","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/comments?post=118"}],"version-history":[{"count":2,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/posts\/118\/revisions"}],"predecessor-version":[{"id":130,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/posts\/118\/revisions\/130"}],"wp:attachment":[{"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/media?parent=118"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/categories?post=118"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/tags?post=118"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}