Subject: [radext] #25: IESG DISCUSS Comments

From: "radext issue tracker" <[email-masked]>
Date: Tue, 08 Jun 2010 14:33:14 -0000

#25: IESG DISCUSS Comments
-----------------------------------+----------------------------------------
 Reporter:  iesg@…                 |       Owner:  aland@…                  
     Type:  defect                 |      Status:  new                      
 Priority:  blocker                |   Milestone:  milestone1               
Component:  tcp-transport          |     Version:  1.0                      
 Severity:  Submitted WG Document  |    Keywords:                           
-----------------------------------+----------------------------------------
 Discusses and other comments

 Summary: Has a DISCUSS. Has enough positions to pass once DISCUSSes are
 resolved.
 Russ Housley

 Comment (2010-05-19)

   Please consider the comments from the Gen-ART Review by Glenn
   Kowack on 18 May 2010.  The review can be found at:

     http://www.softarmor.com/rai/temp-gen-art/
     draft-ietf-radext-tcp-transport-06-kowack.txt

 Lars Eggert

 Comment (2010-05-20)

 Agree with Tim's DISCUSS.

 Section 27, paragraph 13:
 >    It is not intended
 >    to define TCP as a transport protocol for RADIUS in the absence of
 >    TLS.

   The document title is "RADIUS Over TCP". It's surprising to then see
   that abstract say that it is not intended to define RADIUS over TCP...
   Suggestion: Rename document to "Radius over TLS"?

 Section 1., paragraph 1:
 >    While
 >    there are a number of benefits to using UDP as outlined in [RFC2865]
 >    Section 2.4, there are also some limitations:

   Lack of congestion control is surely a limitation?

 Section 1.1., paragraph 2:
 >    In scenarios where RADIUS proxies exchange a large volume of packets
 >    (10+ packets per second), it is likely that there will be sufficient
 >    traffic to enable the congestion window to be widened beyond the
 >    minimum value on a long-term basis, enabling ACK piggy-backing.

   I don't understand what this paragraph means to say. The TCP
   congestion window opens already at much lower rates than 10+ pps.
   Also, how is this at all related to ACK-piggybacking?

 Section 1.1., paragraph 5:
 >    These problems disappear if a 4096 application-layer payload can be
 >    used alongside RADIUS over TLS.  Since most TCP implementations
 >    support MTU discovery, the TCP MSS is automatically adjusted to
 >    account for the MTU, and the larger congestion window supported by
 >    TCP may allow multiple TCP segments to be sent within a single
 >    window.

   Even those few TCP stacks that don't do PMTUD can already support
   arbitrary payloads (just with slightly less efficient packetization).

 Section 2.6.1., paragraph 5:
 >    As noted previously, RADIUS packets SHOULD NOT be re-transmitted to
 >    the same destination IP and numerical port, but over a different
 >    transport layer.

   Where does it say that? The second paragraph of Section 2.6 says that
   they MAY be retransmitted over a new connection (which is different
   from a SHOULD NOT). Also, "transport layer" here is unclear - do you
   mean "transport connection" (= use a different TCP connection) or do
   you mean "transport protocol" (= use UDP)?

 Section 2.6.2., paragraph 2:
 >    Unlike UDP, TLS is subject to issues related to Head of Line (HoL)
 >    blocking.  This occurs when when a TLS segment is lost and a
 >    subsequent TLS segment arrives out of order.  While the RADIUS server
 >    can process RADIUS packets out of order, the semantics of TLS makes
 >    this impossible.  This limitation can lower the maximum packet
 >    processing rate of RADIUS over TLS.

   s/TLS/TCP/ in this paragraph

 Section 2.6.4., paragraph 6:
 >    After applying the above rules, there are still situations where the
 >    previous specifications allow a packet to be "silently discarded".
 >    In these situations, the TCP connections MAY remain open, or MAY be
 >    closed, as an implementation choice.  However, the invalid packet
 >    MUST be silently discarded.

   In order to reduce connection-setup overheads, wouldn't it make sense
   to RECOMMEND the connection stay open?

 Ralph Droms

 Discuss (2010-05-20)

 This Discuss is related to Tim's Discuss.  This text:

    "Bare" TCP transport MAY, however, be used when another method such
    as
 IPSec [RFC4301] is used to provide additional confidentiality and
    security.
 Should experience show that such deployments are useful,
    this specification
 could be moved to standards track.

 is confusing.  Why would experience with
 "bare" TCP or IPSec TCP cause draft-ietf-radext-tcp-transport to progress
 to
 Standards Track?

 Similarly, from the Abstract:

    It [draft-ietf-radext-tcp-transport-06.txt] is not intended
    to define TCP as a transport protocol for RADIUS in the absence of
    TLS.

 while several of the motivations for RADIUS over TCP in section 1.1 are
 not
 specific to RADIUS with TLS.

 Adrian Farrel

 Comment (2010-05-20)

 To follow up on Tim Polk's Discuss point 2
 I appreciate the sentiment of the
 paragraph, but "NOT RECOMMENDED" is not RFC 2119 language (as idnits would
 tell
 you). You have to flip the sense of the sentence and use "RECOMMENDED".
 But Tim
 is also right, please consider "MUST NOT" since the following paragraph...

    "Bare" TCP transport MAY, however, be used when another method such
    as IPSec [RFC4301] is used to provide additional confidentiality and
    security.  Should experience show that such deployments are useful,
    this specification could be moved to standards track.

 ...is really confusing. It implies that the purpose of this document *is*
 to
 define the use of bare TCP transport which is in conflict with the
 Abstract.

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/radext/trac/ticket/25>
radext <http://tools.ietf.org/radext/>

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