DNA BOF S. Daniel Park Internet-Draft SAMSUNG Electronics Category: Informational October 2003 Expires : April 2004 The Latency Statements in DNA draft-park-dna-latency-statements-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 except that the right to produce derivative works is not granted [RFC 2026]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress". The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract In DNA for movement either within a subnet or to different network, various latencies are happened on network devices both host and router. This document tries to analyze what latencies are possible when performing DNA operations. This statement is targeted to Detecting Network Attachment (DNA) as well as to Mobile IPv6. Park Expires - April 2004 [Page 1] Internet-Draft Latency Statements in DNA October 2003 Table of Contents 1. Introduction.................................................2 2. Terminology..................................................3 3. Latencies clarification when performing DNA..................4 4. Summary......................................................7 5. Future Works.................................................8 6. IANA Considerations..........................................8 7. Security Considerations......................................8 8. References...................................................8 9. Author's Address.............................................9 10. Acknowledgements.............................................9 1. Introduction By definition of DNA charter, network attachment occurs when a link- layer connection is established and a node is able to send and receive some IP packets within a link, particularly those used for configuration purposes. This process may occur when link-layer authentication has completed, a host comes back into range of a wireless cell, or a cable is plugged in. The main purpose of DNA is to reduce various latencies when attaching a new network. From reducing, mobile node can obtain IP address and required information as soon as mobile node moves to a new network. The proposed document, [V6DADOPT], clarified the current DAD problems as time delay, but others were out of scope at that time. This document tries to analyze what latencies are possible for mobile node to attach a new network like DHCP latency, AAA latency and router discovery latency, and furthermore describes some problem statement. Some considerations are being simply considered and will be covered with more specific considerations in near future. The wireless lan is a good example for DNA at this stage. Another environment will be covered in near future, but they have low priority just for now. This statement is targeted to Detecting Network Attachment as well as to Mobile IP. Park Expires - April 2004 [Page 2] Internet-Draft Latency Statements in DNA October 2003 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [KEYWORDS]. o DNA Detecting network attachment when mobile nodes move to the new networks. o Latency It means time delay when performing DNA on the mobile node including both layer 2 and layer 3. Almost related terminologies will be covered by DNA Terminology in near future. Park Expires - April 2004 [Page 3] Internet-Draft Latency Statements in DNA October 2003 3. Latencies clarification when performing DNA The following Figure 1 describes the current wireless lan topology in legacy internet. [ AAA Server ] [ DHCP Server] | | | | ----------+---------+-------+---- | | --------------- / \ | IP Backbone | \ / -------+------- | |Carriers |---------------+ +--+--+ +--+--+ | AR1 | | AR2 | +--+--+ +--+--+ | | | | ---+---------+----+--- ----+----- | | | | | | | | | [AP 1] [AP 2] [AP 3] Mobile Node-----> -----> Figure 1. Current wireless lan Topology Park Expires - April 2004 [Page 4] Internet-Draft Latency Statements in DNA October 2003 By DNA definition in charter, layer 3 handover is happened after layer 2 handover is completed. After completing layer 3 handover, mobile node can communicate with internet using new allocated IP address which is generally called care-of address in mobile environment. In DNA for movement within a subnet with a valid address (from AP1 to AP2), there is only a reachability test to the default gateway, and no DAD. DNAv4 is very similar to DNAv6 in terms of the reachability test. Only difference is that ARP is used instead of Neighbor Solicitation (NS) / Neighbor Advertisement (NA). However, in DNA for movement without a subnet which will be allocated different address from now (from AP2 to AP3), it takes a long time to perform layer 2 and layer 3 operation. The following sentences analyze what latencies are possible for DNA both layer 2 and layer 3. (1)802.11 Procedure : Mobile node has to search for what access point is possible to connect in visited network as soon as mobile node moves to a new link. Firstly, 802.11 scan latency is happened. 802.11 scanning is the period for reception of Beacons plus Prob Request/Response from reachable access point in a new network. After then, 802.11 association is happened between mobile node and access point. It is one of latencies. This procedure can go from 45 ~ 450 ms Consideration: The scan time can be reduced by layer 2 trigger [L2TRIGGER]. (2)AAA Procedure : For mobile node authentication, 802.1x authentication procedure is happened between mobile node and AAA (RADIUS) server which is generally stayed beyond access point (access point can provide RADUIS Client, accounting and DHCP Relay) and access router. It also occur DNA latency. Network attachment may occur when link-layer authentication has completed. Consideration: In layer 2 fast handover (such as in 802.11i PMK caching) there is no EAP exchange, just the Association / Reassociation exchange plus 4-way handshake. Park Expires - April 2004 [Page 5] Internet-Draft Latency Statements in DNA October 2003 (3)802.11i Procedure : For enhanced security, 802.11i procedure is used for mobile node and access point including nonce and key generation. 802.1x 4-way handshake comes after EAP-Success (802.1x procedure) and is part of WPA and 802.11i. Though it does not occur long latency, it can be one of DNA latencies. It is not present in pre-standard WEP/802.1x with periodic reauthentication. (4)DHCP Procedure : After link-layer connection is established, mobile node is able to send and receive some IP packets. This procedure considers layer 3 latencies. The mobile node has to perform either DHCP operation which is generally used for DNAv4 or router discovery operation which is generally used for DNAv6 for obtaining IP address and required information from DHCP server and router even if layer 2 operations are completed. Both DHCP server and router are stayed beyond access point and particularly, DHCP server is far from access point which depends on administrator policy. Moreover, DAD (Duplication Address Detection) occurs in DHCPv4 as well as IPv6, because the mobile node needs to check that the IPv4 address handed out by DHCP server is not a duplicate. IPv6 consideration will be covered below sentence. This can take up to 3 seconds. It is a severe case when performing DNA in mobile environment. A proper support for a node to send or receive packets immediately after attaching to a link is undermined by the disruption imposed by the current DAD. (is described in [V6DADOPT]). Consideration: In DNA for movement within a subnet with a valid address, there is only a reachability test to the default gateway (AR1, when mobile node moves to AP2 from AP1), and no DAD (not even optimistic DAD). Specific consideration is described in [DNAv4]. IPv6 DAD latency can be reduced by better algorithms as optimized DAD. IPv6 DAD was described in another document [V6DADOPT]. Park Expires - April 2004 [Page 6] Internet-Draft Latency Statements in DNA October 2003 (5)For IPv6 stateless address autoconfiguration, router discovery is generally used for mobile node to obtain required information from reachable router. There are well known latencies such as mobile node random delay prior to sending RS message as well as router random delay prior to sending RA message, DAD latency to detect address duplication, waiting time to receive RS message either unsolicited or solicited with required information from router. As described in some drafts, this latencies prevent fast handover when moving a new link and conclusively, mobile node can not sustain current connection though. Consideration: For fast router discovery, mobile node can send RS message to router instead of waiting unsolicited RA. These latencies can be reduced by better algorithm: [FASTRA] [FRD]. 4. Summary As described in this document, there are various latencies when performing both DNAv4 and DNAv6 and these latencies prevent fast handover in mobile environment. Conclusively, a proper support for a node to send or receive packets immediately after attaching to a link is undermined by these latencies. For developing optimization to network attachment detection for time-constrained systems such as mobile environment, current latencies should be optimized and reduced by better algorithms which will be covered by another document as solutions in DNA Working Group. In terms of latency, around 40 ms should be layer 2 scanning and 4-way handshake, 5-10 ms is all that should be necessary for a reachability test and configuring the (already valid) IP address (between AP1 and AP2). Layer 2 triggering can be used for mobile node to reduce layer 2 scanning when performing DNA. In DNA for attaching new network (between AP2 and AP3), it will take a little more time to configure the valid IP address. The better algorithms (such as fast router discovery, fast handover, DAD optimization in IPv6, etc.) can be used for reducing latency. Park Expires - April 2004 [Page 7] Internet-Draft Latency Statements in DNA October 2003 5. Future Works o More latencies and considerations ? o Other environments except wireless lan should be considered ? o Relation with DHCPv6 operation 6. IANA Considerations There are no IANA considerations in this document. 7. Security Considerations This document do not occur any security considerations. 8. References [RFC 2026] Bradner, S., The Internet Standards Process - Revision 3, BCP 9, RFC 2026, October 1996. [KEYWORDS] Bradner, S., Key words for use in RFCs to Indicate Requirement Levels, BCP 14, RFC 2119, March 1997. [L2TRIGGER] Alper E. Yegin., Link-layer Triggers Protocol, Internet Draft, June 2002. [V6DADOPT] S. Park, Y, Han, IPv6 DAD Optimization Goals and Requirements, Internet Draft, October 2003. [FASTRA] M. Khalil, J. Kempf, B. Pentland., IPv6 Fast Router Advertisement (FastRA), Internet Draft, September 2003. [FRD] J. Choi, D. Shin., Fast Router Discovery with RA Caching in AP. Internet Draft, Feb 2003. [DNAv4] B. Aboba, Detection of Network Attachment (DNA) in IPv4, Park Expires - April 2004 [Page 8] Internet-Draft Latency Statements in DNA October 2003 Internet Draft, September 2003. 9. Author's Address Soohong Daniel Park Mobile Platform Laboratory, SAMSUNG Electronics Email: soohong.park@samsung.com 10. Acknowledgements Specially thank is due to Bernard Aboba for his many useful comments. Full Copyright Statement Copyright (C) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. 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This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING Park Expires - April 2004 [Page 9] Internet-Draft Latency Statements in DNA October 2003 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Funding for the RFC editor function is currently provided by the internet Society. Park Expires - April 2004 [Page 10]