One document matched: draft-penno-tana-app-practices-recommendation-01.txt

Differences from draft-penno-tana-app-practices-recommendation-00.txt

Transport Working Group                                        R. Penno 
Internet Draft                                         Juniper Networks 
Intended status: Informational                               J. Iyengar 
Expires: May 2009                           Franklin & Marshall College 
                                                       November 3, 2008 
                                    
 
                                      
                    TANA Practices and Recommendations 
           draft-penno-tana-app-practices-recommendation-01.txt 


Status of this Memo 

   By submitting this Internet-Draft, each author represents that       
   any applicable patent or other IPR claims of which he or she is       
   aware have been or will be disclosed, and any of which he or she       
   becomes aware will be disclosed, in accordance with Section 6 of       
   BCP 79. 

   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 

   This Internet-Draft will expire on May 3, 2007. 

Copyright Notice 

   Copyright (C) The IETF Trust (2008). 

Abstract 

   Applications routinely open multiple TCP connections.  For example, 
   P2P applications maintain connections to a number of different peers 
   while web browsers perform concurrent download from the same web 
   server.  Application designers pursue different goals when doing so:  
 
 
 
Penno                    Expires May 3, 2009                   [Page 1] 

Internet-Draft    TANA Practices and Recommendations      November 2008 
    

   P2P apps need to maintain a well-connected mesh in the swarm while 
   web browsers mainly use multiple connections to parallelize requests 
   that involve application latency on the web server side.  But this 
   practice also has impacts to the host and the network as a whole. For 
   example, an application can obtain a larger fraction of the 
   bottleneck than if it had used fewer connections. Although capacity 
   is the most commonly considered bottleneck resource, middlebox state 
   table entries are also an important resource for an end system 
   communication.  

   This documents clarifies the current practices of application design 
   and reasons behind them, and discusses the tradeoffs surrounding the 
   use of many concurrent TCP connections to one destination and/or to 
   different destinations. Other resource types may exist, and the 
   guidelines are expected to comprehensively discuss them.  

Conventions used in this document 

   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 Error! 
   Reference source not found.. 

Table of Contents 

    
   1. Introduction 3 
   2. Terminology 4 
   3. Multiple TCP Connections Advantages 4 
   4. Multiple TCP connections Resources 4 
   5. Memory Space 4 
   6. Link Bandwidth 5 
   7. Middleboxes 5 
   8. Recommendations 6 
      8.1. Diffserv 6 
      8.2. AQM 6 
   9. Security Considerations 6 
   10. IANA Considerations 6 
   11. Conclusions 6 
   12. Acknowledgments 6 
   13. References 7 
      13.1. Normative References 7 
      13.2. Informative References 7 
   Author's Addresses 7 
   Intellectual Property Statement 7 
   Disclaimer of Validity 8 
    
 
 
Penno                    Expires May 3, 2009                   [Page 2] 

Internet-Draft    TANA Practices and Recommendations      November 2008 
    

1. Introduction 

   The use of P2P protocols by end users is widespread. These protocols 
   are meant to exchange, replicate, stream or download files with 
   little human intervention, trying at the same time to minimize the 
   download time of the files requested by any single peer. This is done 
   by opening several connections to multiple peers and downloading one 
   or more chunks of the file from each one, selecting faster peers, 
   amongst others.  

   If we assume that in any file transfer the bottleneck is on the 
   uploading peer or server side, end users that utilize P2P clients in 
   general download the file faster and consume more bandwidth within a 
   specific timeframe than traditional client-server applications. P2P 
   clients can overcome the server side bottleneck by opening multiple 
   connections to different peers. Users of P2P applications also 
   consume bandwidth throughout the whole day since even after a file is 
   fully downloaded it will continue to be shared with others users 
   increasing the upstream bandwidth. 

   We can see then that the advantages of P2P applications come from the 
   fact that they open multiple TCP connection to different peers in 
   order to download multiple pieces of a file in parallel, always look 
   for faster peers. 

   But the use of multiple TCP connections by an application is not new. 
   Web Browsers have being it for a decade. But these are usually short-
   lived connections as opposed to long-lived connections. A long-lived 
   connection in this document should be interpreted as strictly 
   defined, i.e., a TCP connection that is simply in the established 
   state, but not necessarily continuously transferring data. In the 
   case of P2P protocols, e.g. Bittorrent, at any point in time a 
   fraction of these connections is actually sending or receiving data, 
   the others are idle or exchange occasional control information.     

   With the popularity of P2P applications, which maintain hundreds of 
   long-lived TCP connections to multiple hosts, the issue applications 
   making use of multiple TCP connections has been gaining attention. 

   This documents clarifies the current practices of application design 
   and reasons behind them, and discusses the tradeoffs surrounding the 
   use of many concurrent TCP connections to one destination and/or to 
   different destinations. Other resource types may exist, and the 
   guidelines are expected to comprehensively discuss them.  



 
 
Penno                    Expires May 3, 2009                   [Page 3] 

Internet-Draft    TANA Practices and Recommendations      November 2008 
    

2. Terminology 

   Bandwidth: A measure of the amount of data that can be transferred 
   per second. So, if a 1Gb file were transferred within one second the 
   bandwidth consumption during the transfer would be 1Gb/s. If it were 
   transferred within a day, it would be approximately 0.0002Gb/s. 

   Volume: The total number of bytes transferred during a long time 
   period. In both examples above the volume within a day would have 
   been 1Gb.  

   Capacity: The maximum bandwidth a link can sustain continuously. 

   Long-lived connection: A TCP connection that is in the established 
   state but not necessarily continuously transferring data. 

3. Multiple TCP Connections Advantages 

   There are good reasons for an application to use multiple TCP 
   connections. P2P apps need to maintain a well-connected mesh in the 
   swarm while web browsers mainly use multiple connections to 
   parallelize requests that involve application latency on the web 
   server side 

   But from a P2P standpoint multiple TCP connections are at the heart 
   of its functionality. Multiple connections allow for multiple 
   simultaneous downloads, which improve reliability and speed. Multiple 
   connections also allow more effective discovery of new peers, and 
   effective peer-to-peer communication, which allows exchange of 
   information such as which pieces of a file a client has and is 
   available. 

4. Multiple TCP connections Resources 

   Every connected application on the Internet competes for resources. 
   This is not specific to applications that open multiple TCP 
   connections.  The use of multiple TCP connections just amplifies the 
   issue. In the following sections we discuss these resources and how 
   they are amplified by an application opening multiple connections.  

5. Memory Space 

   Each TCP connection needs a TCP control block (TCB) or equivalent to 
   keep state about its connection. In operating systems where the TCP 
   stack is part of the kernel, this would come from the kernel memory 
   space, otherwise from userland memory. 

 
 
Penno                    Expires May 3, 2009                   [Page 4] 

Internet-Draft    TANA Practices and Recommendations      November 2008 
    

   But irrespective from where the memory comes from a TCP control block 
   requires a significant amount of memory. This is significant issue 
   for devices that terminate TCP connections from multiple end hosts to 
   provide functions such as Load-Balancing, Gateway and Tunneling.  

   Some proposals have been put forward to reduce the amount of memory 
   occupied by each TCP control block [RFC2140], but the issue remains 
   significant and is amplified by applications that use multiple TCP 
   connections. 

6. Link Bandwidth 

   The bottlenecks for these n connections could be shared or separate. 
   If separate, there's no specific bottleneck where the connections are 
   hogging bandwidth. But from a network resource point of view, the 
   application download still gets multiple shares.  

   If some/all bottlenecks are shared, then two possibilities exist for 
   shared bottleneck 

   - bottleneck is a last-hop link (user traffic dominates link), OR 

   - bottleneck is in-network wide-area link (background traffic 
   dominates link) 

   If bottleneck is last-hop, then n transport connections compete with 
   each other and share link bandwidth. 

   Although these connections might impact delay-sensitive traffic and 
   increase delay, in the last hop it only affects end end-user, which 
   is in control of which applications run on its host. In this case the 
   user has the option of manually choosing when to run such 
   application, configuring the end host, amongst others. Alternatively, 
   or in conjunction with the above, the application can be enhanced to 
   use Diffserv and new delay sensitive congestion mechanisms. 

   If shared bottleneck is in-network, then application gets unfair 
   share of bottleneck bandwidth. This impacts flows belonging to other 
   users in general, and most importantly delay-sensitive traffic. 

7. Middleboxes 

   Middleboxes re defined as any intermediary box performing functions 
   apart from normal, standard functions of an IP router on the data 
   path between a source host and destination host [RFC3234]. 
   Middleboxes can be stand-alone or integrated in another device such 
   as a router or modem.  
 
 
Penno                    Expires May 3, 2009                   [Page 5] 

Internet-Draft    TANA Practices and Recommendations      November 2008 
    

   The functions that are relevant to this discussion are those that 
   require the middlebox to keep per session state, sometimes referred 
   as transformation services. Some of these functions are, for example, 
   NAT, Intrusion Detection and Load-Balancing. 

   It is easy to see that the more sessions a host initiates, the more 
   state the middlebox will have to keep. The relationship is at least 
   1:1 but due asymmetric traffic, routing changes and others, this can 
   be 1:N. 

   Although application traffic from most broadband subscribers today go 
   through at least one middlebox (integrated into the broadband modem), 
   it can traverse other middleboxes that reside within the ISP's 
   network or close the destination. These middleboxes aggregate traffic 
   from multiple subscribers and state tables within these devices can 
   become a premium.  

8. Recommendations 

8.1. Diffserv 

8.2. AQM 

9. Security Considerations 

   None at this time  

10. IANA Considerations 

   None at this time 

11. Conclusions 

   TBD 

12. Acknowledgments 

    









 
 
Penno                    Expires May 3, 2009                   [Page 6] 

Internet-Draft    TANA Practices and Recommendations      November 2008 
    

13. References 

    

13.1. Normative References 

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 
             Requirement Levels", BCP 14, RFC 2119, March 1997. 

13.2. Informative References 

   [RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and 
             Issues", RFC 3234, February 2002.  

   [RFC2140] J. Touch, TCP Control Block Interdependence, RFC 2140 
             (1997)  

    

Author's Addresses 

   Reinaldo Penno 
   Juniper Networks 
   1194 N Mathilda Aveue 
   Sunnyvale, CA 
       
   Email: rpenno@juniper.net 
    

   Jana Iyengar 
   Franklin & Marshall College 
       
   Email: jiyengar@fandm.edu 
    

Intellectual Property Statement 

   The IETF takes no position regarding the validity or scope of any 
   Intellectual Property Rights or other rights that might be claimed to 
   pertain to the implementation or use of the technology described in 
   this document or the extent to which any license under such rights 
   might or might not be available; nor does it represent that it has 
   made any independent effort to identify any such rights.  Information 
   on the procedures with respect to rights in RFC documents can be 
   found in BCP 78 and BCP 79. 


 
 
Penno                    Expires May 3, 2009                   [Page 7] 

Internet-Draft    TANA Practices and Recommendations      November 2008 
    

   Copies of IPR disclosures made to the IETF Secretariat and any 
   assurances of licenses to be made available, or the result of an 
   attempt made to obtain a general license or permission for the use of 
   such proprietary rights by implementers or users of this 
   specification can be obtained from the IETF on-line IPR repository at 
   http://www.ietf.org/ipr. 

   The IETF invites any interested party to bring to its attention any 
   copyrights, patents or patent applications, or other proprietary 
   rights that may cover technology that may be required to implement 
   this standard.  Please address the information to the IETF at 
   ietf-ipr@ietf.org. 

Disclaimer of Validity 

   This document and the information contained herein are provided on an 
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 
   OR IMPLIED, INCLUDING 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. 

Copyright Statement 

   Copyright (C) The IETF Trust (2008). 

   This document is subject to the rights, licenses and restrictions 
   contained in BCP 78, and except as set forth therein, the authors 
   retain all their rights. 

Acknowledgment 

   Funding for the RFC Editor function is currently provided by the 
   Internet Society. 

    










 
 
Penno                    Expires May 3, 2009                   [Page 8]