Add network related comments into the release notes

Updating the release notes with some of the highlights - especially where
the default behavior now changed (PRR for improved SACK loss recovery).

website/content/en/releases/13.0R/relnotes.adoc

@@ -175,6 +175,8 @@ This section covers changes and additions to devices and device drivers since {r
 
 This section covers changes and additions to file systems and other storage subsystems, both local and networked.
 
+For {{< manpage "iscsi" "4" >}} and {{< manpage "ctld" "8" >}}, support for specifying network QoS in the form of DiffServ Codepoints (DSCP) and Ethernet Priority Code Point (PCP) was added. {{< commit "ddf1072aac49" >}} {{< sponsored "NetApp" >}}
+
 [[storage-general]]
 === General Storage
 
@@ -193,6 +195,18 @@ This section covers the boot loader, boot menu, and other boot-related changes.
 
 This section describes changes that affect networking in FreeBSD.
 
+For {{< manpage "tcp" "4">}}, Proportional Rate Reduction, as described by RFC6937, to improve SACK loss recovery during burst loss and ACK thinning scenarios, was implemented and is enabled by default.
+A new {{< manpage "sysctl" "8" >}} has been added, `net.inet.tcp.do_prr`, which when set to `0` will restore the prior behavior.
+It is expected that PRR generally helps improve loss recovery performance and prevent numerous preventable RTO stalls.
+This surpasses the prior behavior, but a strictly packet conserving variant can be enabled.
+When misconfigured token bucket traffic policer can cause persistent loss even during loss recovery, activating the conservative PRR variant may prevent some retransmission timeouts (RTO) and associated session stalls for a few milliseconds while behaving less optimal in the general case.
+For this, a new {{< manpage "sysctl" "8">}} was added, `net.inet.tcp.do_prr_conservative`.
+Setting this variable to `1` will enable strictly packet conserving behavior (at most 1 segment for each ACK received), while the normal variant may send up to 2 segments per received ACK - helping in cases of ACK thinning or significant burst loss events.  {{< commit "0e1d7c25c5ab" >}} {{< sponsored "NetApp" >}}
+
+The {{< manpage "cc_cubic" "4">}} has been improved to address various corner cases and align more closely with the standard in RFC8312. {{< commit "40f9078ff9d9" >}} {{< sponsored "NetApp" >}}
+
+The {{< manpage "ping" "8" >}} and {{< manpage "ping6" "8" >}} utilities both support setting network QoS, with IP DSCP {{< commit "6034024daddb" >}} and Ethernet PCP {{< commit "81a6f4c7ae69" >}} {{< sponsored "NetApp" >}}
+
 [[network-general]]
 === General Network