Re: use TCP_NODELAY on TCP sockets?
On Thu, May 16, 2024 at 12:55:38PM +0200, Ondrej Zajicek wrote: > Yeah, i think that using TCP_NODELAY for BGP makes sense, considering > there is already non-trivial framing and we write individual BGP > messages with one write(). I suspect it might be better for throughput to send multiple BGP messages with a single writev() or sendmsg() call. Kind regards, Job
Re: use TCP_NODELAY on TCP sockets?
Hello Douglas, just a really fast response, we aren't going to implement BGP over QUIC at all, at least when TLS is a required part of QUIC. There are some thoughts about BGP 5 being encoded as CBOR and sent over something like QUIC, anyway it doesn't make any sense to introduce QUIC to BGP now. Maria On Thu, May 16, 2024 at 09:45:56AM -0300, Douglas Fischer wrote: > I'm not a programmer, and I know almost nothing about it... > > But reading this thread, I remembered this draft about BGP-over-QUIC. > https://datatracker.ietf.org/doc/draft-retana-idr-bgp-quic/ > > I'm not sure what I'm going to say, but I have the impression that the > session closure control method that will be chosen may have something to do > with this BoQ idea. > > I don't even know if what I'm saying makes any sense or not. > But if you do, it may be something that you have to take into consideration > when choosing the method. > > And besides, there are many other "ifs"... > We don't even know if this Draft will actually become an RFC. And if it > becomes RFC, we don't even know if it will have traction. > We also don't know if the IBRD project will adhere to this protocol, etc... > > But, I thought it was opportune to mention. > > Em qui., 16 de mai. de 2024 às 07:59, Ondrej Zajicek > escreveu: > > > On Wed, May 15, 2024 at 06:37:18PM +0200, Job Snijders via Bird-users > > wrote: > > > > > Dear BIRD people, > > > > > > On most systems RFC 896 TCP congestion control is used, also known as > > > "Nagle's algorithm". This algorithm is intended to help coalesce > > > consecutive small packets from userland applications (like BIRD) into a > > > single larger TCP packet. The idea being it reduces bandwidth because > > > there is less TCP overhead if data is bundled into fewer packets. > > > ... > > > I think using TCP_NODELAY is interesting to consider, because it seems > > > sensible to try to deliver BGP messages as fast as possible. OpenBGPD > > > and FRR set the TCP_NODELAY socket option. > > > > Hi > > > > Yeah, i think that using TCP_NODELAY for BGP makes sense, considering > > there is already non-trivial framing and we write individual BGP messages > > with one write(). > > > > -- > > Elen sila lumenn' omentielvo > > > > Ondrej 'Santiago' Zajicek (email: santi...@crfreenet.org) > > "To err is human -- to blame it on a computer is even more so." > > > > > -- > Douglas Fernando Fischer > Engº de Controle e Automação -- Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.
Re: use TCP_NODELAY on TCP sockets?
I'm not a programmer, and I know almost nothing about it... But reading this thread, I remembered this draft about BGP-over-QUIC. https://datatracker.ietf.org/doc/draft-retana-idr-bgp-quic/ I'm not sure what I'm going to say, but I have the impression that the session closure control method that will be chosen may have something to do with this BoQ idea. I don't even know if what I'm saying makes any sense or not. But if you do, it may be something that you have to take into consideration when choosing the method. And besides, there are many other "ifs"... We don't even know if this Draft will actually become an RFC. And if it becomes RFC, we don't even know if it will have traction. We also don't know if the IBRD project will adhere to this protocol, etc... But, I thought it was opportune to mention. Em qui., 16 de mai. de 2024 às 07:59, Ondrej Zajicek escreveu: > On Wed, May 15, 2024 at 06:37:18PM +0200, Job Snijders via Bird-users > wrote: > > Dear BIRD people, > > > > On most systems RFC 896 TCP congestion control is used, also known as > > "Nagle's algorithm". This algorithm is intended to help coalesce > > consecutive small packets from userland applications (like BIRD) into a > > single larger TCP packet. The idea being it reduces bandwidth because > > there is less TCP overhead if data is bundled into fewer packets. > > ... > > I think using TCP_NODELAY is interesting to consider, because it seems > > sensible to try to deliver BGP messages as fast as possible. OpenBGPD > > and FRR set the TCP_NODELAY socket option. > > Hi > > Yeah, i think that using TCP_NODELAY for BGP makes sense, considering > there is already non-trivial framing and we write individual BGP messages > with one write(). > > -- > Elen sila lumenn' omentielvo > > Ondrej 'Santiago' Zajicek (email: santi...@crfreenet.org) > "To err is human -- to blame it on a computer is even more so." > -- Douglas Fernando Fischer Engº de Controle e Automação
Re: use TCP_NODELAY on TCP sockets?
send(..., MSG_MORE) send(..., 0) Is roughly equivalent to setsockopt(..., TCP_CORK, 1) send(..., 0) send(..., 0) setsockopt(..., TCP_CORK, 0) In cases where you know that you're going to write more but you want to be able to discard the user space buffer, MSG_MORE is useful. If holding onto the buffers is easy so they can then be passed to sendmsg(), then you may as well do that. (And of course you can combine both techniques) - Erin On Thu, 16 May 2024, at 01:32, Job Snijders wrote: > On Wed, May 15, 2024 at 09:09:47PM +0200, Erin Shepherd wrote: > > It seems absent from the BSDs, but on Linux you can pass the MSG_MORE > > flag to send() to override TCP_NODELAY for a specific write > > Am I understanding correctly this is a variant on TCP_NOPUSH/TCP_CORK? > "more data is coming, dont push the send button yet!" > > In OpenBGPD, TCP_NODELAY is set on the socket (a socket option available > on all platforms, I think?), and then all data is coalesced into > sendmsg(), no need for 'corking'. From my limited testing it seems a > full routing table should fit in ~ TCP 41,000 packets. > > BIRD has a code path sk_sendmsg()->sendmsg() called from > sk_maybe_write(); but based my limited testing I'm not sure this path is > followed in all cases, because I see way more than 41K packets for a > full table feed (with TCP_NODELAY enabled). > > Perhaps there are two separate questions here: > > - are BGP messages (slightly) delayed because of TCP_NODELAY not being > set? (I think yes) > - are BGP messages as efficiently coalesced into as few TCP packets as > possible? (with TCP_NODELAY set, I am not sure) > > Kind regards, > > Job > > ps. To clarify why I started this thread: last week I fell into the TCP > subsystem rabbit hole: why are things the way they are? I started > auditing various programs related to my $dayjob and thought it would be > good to open a conversation with the BIRD developer community. My goal > is not necessarily to get this patch 'as-is' merged, but to learn from > and with friendly and respected BGP developers. >
Re: use TCP_NODELAY on TCP sockets?
On Wed, May 15, 2024 at 06:37:18PM +0200, Job Snijders via Bird-users wrote: > Dear BIRD people, > > On most systems RFC 896 TCP congestion control is used, also known as > "Nagle's algorithm". This algorithm is intended to help coalesce > consecutive small packets from userland applications (like BIRD) into a > single larger TCP packet. The idea being it reduces bandwidth because > there is less TCP overhead if data is bundled into fewer packets. > ... > I think using TCP_NODELAY is interesting to consider, because it seems > sensible to try to deliver BGP messages as fast as possible. OpenBGPD > and FRR set the TCP_NODELAY socket option. Hi Yeah, i think that using TCP_NODELAY for BGP makes sense, considering there is already non-trivial framing and we write individual BGP messages with one write(). -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santi...@crfreenet.org) "To err is human -- to blame it on a computer is even more so."
