Draft: draft-ietf-ice-rfc5245bis

Commentary: The usage of no - op mechanism and RTP comfort noise mechanism for keepalives have been removed . Also , the keepalive procedures when communicating with a non - ICE peer , and when ICE is not used at all , have been removed .
All endpoints MUST send keepalives for each media session.  These
keepalives serve the purpose of keeping NAT bindings alive for the
media session.  These keepalives MUST be sent even if ICE is not
being utilized for the session at all.  The keepalive SHOULD be sent
using a format that is supported by its peer.  ICE endpoints allow
for STUN-based keepalives for UDP streams, and as such, STUN
keepalives MUST be used when an agent is a full ICE implementation
and is communicating with a peer that supports ICE (lite or full).
If the peer does not support ICE, the choice of a packet format for
keepalives is a matter of local implementation.  A format that allows
packets to easily be sent in the absence of actual media content is
RECOMMENDED.  Examples of formats that readily meet this goal are RTP
No-Op I-D.ietf-avt-rtp-no-op, and in cases where both sides support
it, RTP comfort noise RFC3389.  If the peer doesn't support any
formats that are particularly well suited for keepalives, an agent
SHOULD send RTP packets with an incorrect version number, or some
other form of error that would cause them to be discarded by the
peer.
If there has been no packet sent on the candidate pair ICE is using
for a media component for Tr seconds (where packets include those
defined for the component (RTP or RTCP) and previous keepalives), an
agent MUST generate a keepalive on that pair.  Tr SHOULD be
configurable and SHOULD have a default of 15 seconds.  Tr MUST NOT be
configured to less than 15 seconds.  Alternatively, if an agent has a
dynamic way to discover the binding lifetimes of the intervening
NATs, it can use that value to determine Tr.  Administrators
deploying ICE in more controlled networking environments SHOULD set
Tr to the longest duration possible in their environment.
All endpoints MUST send keepalives for each media session.  These
keepalives serve the purpose of keeping NAT bindings alive for the
media session.  The keepalives SHOULD be sent using a format that is
supported by its peer.  ICE endpoints allow for STUN-based keepalives
for UDP streams, and as such, STUN keepalives MUST be used when an
agent is a full ICE implementation and is communicating with a peer
that supports ICE (lite or full).
If there has been no packet sent on the candidate pair ICE is using
for a media component for Tr seconds (where packets include those
defined for the component (RTP or RTCP) and previous keepalives), an
agent MUST generate a keepalive on that pair.  ICE endpoints SHOULD
use a Tr value of 15 seconds, but MAY use another value, e.g. based
on configuration or network/NAT characteristics.  For example, if an
agent has a dynamic way to discover the binding lifetimes of the
intervening NATs, it can use that value to determine Tr.
Administrators deploying ICE in more controlled networking
environments SHOULD set Tr to the longest duration possible in their
environment.  ICE endpoints MUST NOT use a Tr value smaller than 15
seconds.