Hi In addition to the below, in NR (=New Radio, a part of 5G) the RLC layer will no longer ensure in sequence delivery to higher layers. Packet reordering can occur on the MAC layer as several HARQ (Hybrid ARQ) run simultaneously to transmit packets, some processes need to retransmit and there you get packet reordering. The PDCP layer can however (optionally) enforce in sequence delivery, personally I am sceptic about the benefits of this as it adds extra HoL blocking to solve a problem that RACK can solve. In addition it costs more memory in nodes that potentially need to transmit 10s of GByte of data. /Ingemar ====== Date: Tue, 12 Mar 2019 21:39:42 -0700 (PDT) From: David Lang To: Sebastian Moeller Cc: Mikael Abrahamsson , "Holland, Jake" , Cake List , "codel@lists.bufferbloat.net" , bloat , "ecn-sane@lists.bufferbloat.net" Subject: Re: [Bloat] [Cake] The "Some Congestion Experienced" ECN codepoint - a new internet draft - Message-ID: Content-Type: text/plain; charset=US-ASCII; format=flowed On Mon, 11 Mar 2019, Sebastian Moeller wrote: > How is packet reordering for anybody but the folks responsible for > operating the "conduits" in any way attractive? It's more that not worrying about maintaining the order, and just moving the packets as fast as possible reduces the overhead. The majority of the time, packets will be in order, but race conditions and corner cases are allowed to forward packets out of order rather than having the delay some packets to maintain the order. David Lang