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<reference anchor='RFC2481'>

<front>
<title abbrev='ECN to IP'>A Proposal to add Explicit Congestion Notification (ECN) to IP</title>
<author initials='K.K.' surname='Ramakrishnan' fullname='K. K. Ramakrishnan'>
<organization>AT&amp;T Labs. Research</organization>
<address>
<phone>+1 973 360 8766 </phone>
<email>kkrama@research.att.com</email>
<uri>http://www.research.att.com/info/kkrama</uri></address></author>
<author initials='S.' surname='Floyd' fullname='Sally Floyd'>
<organization>Lawrence Berkeley National Laboratory</organization>
<address>
<phone>+1 510 486 7518</phone>
<email>floyd@ee.lbl.gov</email>
<uri>http://www-nrg.ee.lbl.gov/floyd/</uri></address></author>
<date month='January' year='1999' />
<area>Internet</area>
<keyword>congestion</keyword>
<keyword>multicast</keyword>
<abstract>
<t>
   This note describes a proposed addition of ECN (Explicit Congestion
   Notification) to IP.  TCP is currently the dominant transport
   protocol used in the Internet. We begin by describing TCP&apos;s use of
   packet drops as an indication of congestion.  Next we argue that with
   the addition of active queue management (e.g., RED) to the Internet
   infrastructure, where routers detect congestion before the queue
   overflows, routers are no longer limited to packet drops as an
   indication of congestion.  Routers could instead set a Congestion
   Experienced (CE) bit in the packet header of packets from ECN-capable
   transport protocols.  We describe when the CE bit would be set in the
   routers, and describe what modifications would be needed to TCP to
   make it ECN-capable.  Modifications to other transport protocols
   (e.g., unreliable unicast or multicast, reliable multicast, other
   reliable unicast transport protocols) could be considered as those
   protocols are developed and advance through the standards process.
</t></abstract></front>

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