Draft: draft-irtf-nwcrg-network-coding-satellites-06

Commentary: Answer to issue 
 A first sentence says quasi - error - free is usually guarranteed thanks to redundancy , while the following sentence tends to say the opposite . Not very clear . The intro fails to clarify the targets . Among them there is " coding to recover from packet losses " ( to avoid confusion with bit - error corrections ) , but also " coding to improve the usage of radio resource " . You should also clarify better what is meant by coding : it 's not a content coding ( e.g. , to compress a video flow ) but rather a computation of linear combination of packets . Say since the begining you 'll rely on RFC8406 whenever possible . Parts of the text currently in section 3 ( 1st paragraph ) deserve to be moved here . Typo : s / to cope from / to cope with/ 
 We have updated the introduction structure and changed the usage of coding in the whole document . We hope this is better . cf PR and PR 
 this is cherrypicking , not discussing link / channel FEC ( Error ) or ACK . the heading should really be ' of network coding schemes ' . " to cover cases where where " ? At the physical layer , FEC mechanisms can be exploited.-- Erasure or Error ? " Based on public information , coding does not seem to be widely used at higher layers . " it is n't , and that section can be reduced to just that sentence . 
 Vincent in item X1 , 1st sentence , it suggests QUIC is a video streaming application . Change it .  . 2 raises a general question : it refers to upper applications that are by nature on the end - hosts . Everything is imaginable here and this is not specific to a SATCOM system . Why do n't you limit yourself to the communication layers + middleware ? I 'm a bit confused . When you say : " Based on public information , coding does not seem to be widely used at higher layers . " I guess you limit yourself to the " packetization UDP / IP + middleware " but do not consider upper applications . It 's also confusing . 
 We think that these comments have been assessed with PR 
 " However , physical layer reliability mechanisms may not recover transmission losses ( e.g. with a mobile user ) and layer 2 ( or above ) re - transmissions induce 500 ms one - way delay with a geostationary satellite " Look , forward error coding ( FEC ) and link ACKs are complementary on a sliding scale depending on delay / channel quality , and this is talking solely about retransmissions . In fact , link or channel FEC do recover a large number of transmission bit / symbol losses without adding extra delay . 
 We have clarified this point in PR
Guaranteeing both physical-layer robustness and efficient usage of
the radio resource has been in the core design of SATellite
COMmunication (SATCOM) systems.  The trade-off often resided in how
much redundancy a system adds to cope from link impairments, without
reducing the good-put when the channel quality is high.  There is
usually enough redundancy to guarantee a Quasi-Error Free
transmission.  However, physical layer reliability mechanisms may not
recover transmission losses (e.g. with a mobile user) and layer 2 (or
above) re-transmissions induce 500 ms one-way delay with a
geostationary satellite.  Further exploiting coding schemes at higher
OSI-layers is an opportunity for releasing constraints on the
physical layer in such cases and improving the performance of SATCOM
systems.
Guaranteeing both physical-layer robustness and efficient usage of
the radio resource has been in the core design of SATellite
COMmunication (SATCOM) systems.  The trade-off often resided in how
much redundancy a system adds to cope from link impairments, without
reducing the good-put when the channel quality is good.  There is
usually enough redundancy to guarantee a Quasi-Error Free
transmission.  The recovery time depends on the encoding block size.
Considering for instance geostationary satellite system (GEO),
physical or link layers erasure coding mechanisms recover
transmission losses within a negligible delay compared to link delay.
However, when retransmissions are triggered, this leads to an non-
negligible additional delay in particular over GEO link.  Further
exploiting coding schemes at application or transport layers is an
opportunity for releasing constraints on the physical layer and
improving the performance of SATCOM systems.