Internet DRAFT - draft-xu-mptcp-momp

draft-xu-mptcp-momp



Network Working Group                                     Changqiao Xu 
Internet Draft                                                   BUPT 
Intended status: Experimental                              Jiuren Qin 
Expires: December 2017                                           BUPT 
                                                          Hongke Zhang 
                                                                 BUPT 
                                                        Chunshan Xiong 
                                          Huawei Technologies Co., Ltd 
                                                              Lei Zhu 
                                          Huawei Technologies Co., Ltd 
                                                         June 21, 2017 
 
  
                      A Message-Oriented Extension to  
              Multipath Transmission Control Protocol (MPTCP)  
                        draft-xu-mptcp-momp-04.txt 


Status of this Memo 

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Internet-Draft          Message-Oriented MPTCP            December 2016 


   The list of Internet-Draft Shadow Directories can be accessed at 
   http://www.ietf.org/shadow.html
   This Internet-Draft will expire on December 3, 2016. 

Copyright Notice 

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Abstract 

   This memo specifies a message-oriented extension for Multipath TCP 
   (MPTCP) which aims to serve high-bandwidth and real-time 
   applications. By introducing a message mapping to MPTCP, Message-
   Oriented MPTCP (MO-MPTCP) attaches some message features like 
   boundaries, priority and dependency to bytestream. With such 
   message-oriented information, MPTCP senders can avoid the waste of 
   transmission resources and improve the transmission efficiency. 


Table of Contents 


   1. Introduction .............................................. 3 
   2. Conventions ............................................... 3 
   3. New Functionalities provided by MO-MPTCP .................. 3 
   4. Message Mapping ........................................... 4 
  5. Operations of MO-MPTCP .................................... 6 
      5.1. Boundary-Based Packet Scheduling ..................... 6 
      5.2. Message-Oriented Transmission Optimization ........... 8 
   6. Interface Considerations .................................. 8 
   7. Security Considerations ................................... 9 
   8. IANA Considerations ....................................... 9 
   9. References ................................................ 9 
      9.1. Normative References ................................. 9 
      9.2. Informative References ............................... 9 
   10. Acknowledgments .......................................... 9 

 
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1. Introduction 

   With the increasingly demands for bandwidth-intensive services, e.g., 
   high-definition (HD) video, the streaming media data which is 
   massive, ordered and delay-sensitive is becoming the main traffic of 
   transport layer. Usually, the streaming media data is transferred by 
   UDP (User Datagram Protocol) which performs better than TCP 
   (Transmission Control Protocol) in improving throughput and reducing 
   latency. However, UDP does not have congestion control mechanism and 
   may result in network collapses.  

   MPTCP which has been standardized in [RFC6824] can greatly improve 
   the throughput of one association by concurrently transferring data 
   on several TCP subflows. Furthermore, the congestion control 
   mechanism provided by MPTCP can make it work without starving TCP. 
   With these advantages, MPTCP has the potential to serve the high-
   bandwidth and real-time applications. 

   This memo introduces a Message-Oriented MPTCP (MO-MPTCP) which is a 
  light and scalable extension to standard MPTCP [RFC6824] and more 
   suitable for streaming media transfer. MO-MPTCP specifies a message 
   mapping to record the information about message boundaries, priority 
   and dependency in the connection level. Based on this mapping, MO-
   MPTCP offers Boundary-Based Packet Scheduling Mechanism which can 
   avoid unnecessary transmission and Message-Oriented Transmission 
   Optimization which can preferentially ensure the transmission of 
   important data. 

2. Conventions 

   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 [RFC2119].  

3. New Functionalities provided by MO-MPTCP 

   Making the transmission of stream media as an example, the new 
   functionalities provided by Message-Oriented MPTCP are as follows: 

   o Boundary-Based Packet Scheduling 

   In the process of stream media transmission, application layer 
   usually delivers the data to the transport layer frame by frame. 
   Each frame can be seen as an individual message. However, in the 
   transport layer, limited by Maximum Segment Size (MSS) MPTCP tends
   to segment the big messages and splice the small messages. And it 
   also splice the small messages into one data packets to reduce 
 
 
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   transmission overhead. In general, all data are transferred in the 
   size of MSS. The segmentation and splicing operation of transport 
   layer leads to lose the original message boundaries. MO-MPTCP 
   provides a message mapping that can record the features of 
   application messages including boundaries, priority and dependency,
   etc.. This mapping can help the sender to avoid unnecessary
   transmissions. For example, stream media can usually tolerate the 
   loss of partial packets, which means the sender can give 
  transmission up and notify the receiver when a packet is considered 
   as time out. This kind of partially reliable mechanism can refer to 
   [PRMP]. In this situation, if a packet which contains partial data 
   of a frame data is abandoned by the sender, as a result, this frame 
   cannot be decoded correctly at receiver side with the absence of 
   partial information. Current MPTCP which is based on bytestream 
   fails to perceive this situation, and still transmits the remaining 
   data of this frame which is a waste of transmission resources. In 
   Message-Oriented MPTCP, thanks to the recording of message boundary,
   senders can abandon the remaining data simultaneously and avoid 
   unnecessary transmission. 

   o Message-Oriented Transmission Optimization 

   Traditional transmission ignores the priority and dependency of 
   messages and treats them equally as a bytestream, which makes the 
   transport blindly. Using an IPMH-like [IPMH] interface, MO-MPTCP can 
   get the priority of each message, and record the dependency between 
   them. For instance, in the standard MPEG coding, "I" frames are 
   essential to the recovery of the whole images and can be decoded 
   independently, so they have the "HIGH" priority and Dependency is 
   "NULL". Similarly, "P" frames which are decoded based on a previous 
   frame have "MEDIUM" priority and Dependency is "PRE". "B" frames 
   which are decoded based on both a previous frame and a latter frame 
   have "LOW" priority and Dependency is "PRE&LAR". Through some rules, 
   TCP packets can determine their own priorities from the messages 
   priorities. The reliability and timeliness of high-priority packets 
   will be guaranteed first when congestion occurs. When a duplicate 
   acknowledgement is received in the subflow level, the sender will 
   execute judgment for the missing packet upon their priorities and 
   duplicate ACK numbers. The send then will retransmit the packet if 
   needed. 

4. Message Mapping 

   MO-MPTCP sets up a Message Mapping in the connection level. The 
   Message Mapping which is similar to the Data Sequence Mapping can 
   associates message features such as boundary and priority with 
   stream features such as DSN. This mapping which is the foundation of 
   MO-MPTCP can provide useful information for data scheduling in 
   transmission. 
 
 
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   The Message Mapping consists of a lot of records, and each record 
   corresponds to an application message. Its structure sketch is show 
   in Figure 1.  

                         +----------------------+ 
                         |   Message Mapping    | 
                         +----------------------+ 
                         |    Message Type 1    | 
                         |        DSN 1         | 
                         |       Length 1       | 
                         |      Priority 1      | 
                         |    Dependency 1      | 
                         +----------------------+ 
                         |    Message Type 2    | 
                         |        DSN 2         | 
                         |       Length 2       | 
                         |      Priority 2      | 
                         |    Dependency 2      | 
                         +----------------------+ 
                         \          .           / 
                         /          .           \ 
                         +----------------------+ 
                         |    Message Type N    | 
                         |        DSN N         | 
                         |       Length N       | 
                         |      Priority N      | 
                         |    Dependency N      | 
                         +----------------------+ 
                         Figure 1 Message Mapping 

   o Message Type is used to distinguish the classes of message. It 
     can change its meaning depending on the application. For example, 
     in the streaming media transmission, it represents which kind of 
     frame this message is. 

   o DSN=Data Sequence Number. DSN shows the Data Sequence Number of 
     the first byte in an application message. 

   o Length shows the number of bytes that this message contains. This 
     parameter is usually used with DSN, and can identify the message 
     boundaries. 

   o Priority shows the importance of this message which usually be 
      divided into three priority HIGH, MEDIUM, LOW. 



 
 
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   o Dependency shows the dependencies between adjacent messages. For 
     example, "NULL" means this message is independent; "PRE" means 
     this message depends on the previous message to be decoded; "LAT"
     means this message depends on the later message to be decoded. 
     "PRE&LAT"means this message depends on both the previous and 
     later messages to be decoded. 

   The DSN and Length are used to identify the boundary of an 
   application message. And, the rest of the parameters which are 
   unique nature of messages are used to provide information for the 
   transmission optimization. 

   MO-MPTCP also provides rules for mapping establishment and removal 
   as follows: 

   o On receiving an application message, the sender SHOULD add a new 
     record containing all necessary parameters to the Message Mapping. 
     However these parameters may have different meaning for different 
     applications. 

   o When receiving an ACK in the MPTCP connection level, the sender 
     SHOULD judge whether need to remove some records from the Message 
     Mapping. Some messages are larger than the MSS, and may be partly 
     acknowledged. MO-MPTCP provisions that the record for a message 
     SHOULD be retained until all segments of this message are 
     acknowledged. 

5. Operations of MO-MPTCP 

5.1. Boundary-Based Packet Scheduling 

   Boundary-Based Packet Scheduling is used in the situations where the 
   applications can tolerate the loss of some packages to meet its 
   requirements for timeliness. [PRMP] proposed a partially reliable 
   extension to MPTCP called PR-MPTCP, which is designed to deal with 
   above situations. However, PR-MPTCP is based on the bytestream and 
   can perform better with the help of MO-MPTCP. For instance, if a TCP 
   packet containing partial data of a message is determined to be 
   discarded, MO-MPTCP can find and discard the remaining data that 
   belongs to or relies on this message. The detailed operating steps 
   are as follows: 

   a) MO-MPTCP offers a function to the sender. When determining to 
      discard a packet, the sender SHOULD call thi s function and send 
      the starting DSN and length of this packet as parameters to MO-
      MPTCP. 

 
 
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   b) Every time receiving calling from the sender, MO-MPTCP SHOULD 
      search the Message Mapping and record all the messages involved in 
      this packet. 

   c) Based on the messages selected by step b) MO-MPTCP then refers 
      to the Dependency recorded in Message Mapping and extracts some 
      other messages which rely on them to be decoded. 

   d) MO-MPTCP combines all the messages selected by step b) and c) 
      and connects them as one or more bigger messages according to 
      their DSNs and Length. Then the new boundaries of these messages 
      are obtained. 

   e) MO-MPTCP SHOULD return the starting DSN and Length of these new 
      messages. Then, the sender can continue its original operations 
      and discard the expanded messages according to the new boundaries. 

    Step b) can be classified into the following situations: 

   o Only one message is involved in the packet, which means this 
     packet is just a segment of the original message. In this case, 
     MO-MPTCP SHOULD search the Message Mapping and record this 
     message. 

   o Two or more messages are involved in the packet, which means this 
     packet contains data comes from different messages. In this case, 
     MO-MPTCP SHOULD search the Message Mapping and record all related 
     messages. 

  When executing step c) there are some notes: 

   o Before starting to search the Message Mapping, MO-MPTCP 
     preferably checks the priorities of the messages provided by step 
     b) and skips the messages which have LOW priority. Because 
     there is usually no message relies on them. 

   o Although the parameter of Dependency in Message Mapping only 
     reflects the relationship between adjacent messages, the lost a 
     message with HIGH priority can influence several messages with 
     lower priority. For example, if an "I" frame is decided to be 
     discarded, the following several frames will be influenced. So, 
     the implementation should pay attention to a chain reaction. 





 
 
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Internet-Draft          Message-Oriented MPTCP           December 2016 

5.2. Message-Oriented Transmission Optimization 

   The Message Mapping records the priorities of the messages. Based on 
   these priorities, each TCP packet can determine its own priority. 
   The basic rules are as follows: 

   o If the data of a packet comes from only one message, the packet 
     priority is the same with the message priority. 

   o If the data of a packet comes from several messages, the packet 
     priority is the same with the highest message priority. 

   Following the above rules, senders can obtain the packet priority, 
   which is an important reference for the transmission optimization. 
   The main operations of the optimization are as follows: 

   a) Once the sender receives duplicate acknowledgement, it SHOULD 
      obtain the priority of those corresponding TCP packets by 
      searching the Message Mapping. 

   b) MO-MPTCP determines whether these packets need being 
      retransmitted immediately based on their priorities and the number 
      of duplicate acknowledgments. The packets with HIGH priority 
      will not be easily discarded;The packets with LOW priority will be 
      discarded first when congestion occurs. 

   c) If a TCP packet is judged to need retransmission by step b) the 
      senders SHOULD retransmit it immediately. Meanwhile, it SHOULD 
      also reset retransmission timer and clear the number of duplicate 
      acknowledgment. 

   d) If a TCP packet does not need to be transmitted after step b) 
      the senders can continue their original works until event in step 
      a) happens.

6. Implementation Consideration 

   In order to achieve message-oriented control and byte-oriented 
   transport, MO-MPTCP records the message information in the Message 
   Mapping. In the implementations of MO-MPTCP, hosts have to reserve 
   some memory for Message Mapping, which brings additional cost. 
   However, with the help of Message Mapping, more intelligent and 
   efficient transmission can be achieved. And the additional cost is 
   reasonable and tolerable. 
 
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7. Interface Considerations 

   MO-MPTCP offers an interface to the upper layer, through which the 
   applications can call MO-MPTCP and assign the parameters like 
   priority and dependency. The ways in which application obtain these 
   parameters can refer to [IPMH]. 

8. Security Considerations 

   This memo develops no new security scheme for MPTCP. MO-MPTCP share 
   the same security issues discussed in [RFC6824] with MPTCP. 

9. IANA Considerations 

   There is no IANA consideration for this memo. 

10. References 

10.1. Normative References 

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

   [RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, 
             "TCP Extensions for Multipath Operation with Multiple 
             Addresses", RFC 6824, January 2013. 

    10.2. Informative References 

   [PRMP]   Changqiao Xu, H. Huang, H. Zhang, C. Xiong, L. Zhu 
            "Multipath Transmission Control Protocol (MPTCP) Partial 
             Reliability Extension? draft-xu-mptcp-prmp-02, September 
             2015. 

   [IPMH]    E, Gineste M, Dairaine L, et al. Building self-optimized 
             communication systems based on applicative cross-layer 
             information. Computer Standards & Interfaces, 2009, 
             31(2): 354-361. 

11. Acknowledgments 

   This Internet Draft is the result of a great deal of constructive 
   discussion with several people, notably Man Tang, Hui Huang, and 
   Peng Wang. 

   This document was prepared using 2-Word-v2.0.template.dot. 

 
 
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   Authors' Addresses

   Changqiao Xu 
   Beijing University of Posts and Telecommunications 
   Institute of Network Technology, No. 10, Xitucheng Road, 
   Haidian District, Beijing 
   P.R. China 
  
   Email: cqxu@bupt.edu.cn 


   Jiuren Qin 
   Beijing University of Posts and Telecommunications 
   Institute of Network Technology, No. 10, Xitucheng Road, 
   Haidian District, Beijing 
   P.R. China 
  
   Email: jrqin@bupt.edu.cn 


   Hongke Zhang 
   Beijing University of Posts and Telecommunications 
   Institute of Network Technology, No. 10, Xitucheng Road, 
   Haidian District, Beijing 
   P.R. China 
  
   Email: hkzhang@bupt.edu.cn 

   Chunshan Xiong 
   Huawei Technologies Co., Ltd 
   Science and Technology Demonstration Garden, No. 156, Zhongguancun 
   North Qing Road, 
   Haidian District, Beijing 
   P.R. China 
  
   Email: sam.xiongchunshan@huawei.com 

   Lei Zhu 
   Huawei Technologies Co., Ltd 
   Science and Technology Demonstration Garden, No. 156, Zhongguancun 
   North Qing Road, 
   Haidian District, Beijing 
   P.R. China 
  
   Email: lei.zhu@huawei.com 


 
 
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