TOC 
Network Working GroupY. Hong
Internet-DraftETRI
Intended status: InformationalJ. Youn
Expires: January 13, 2011DONG-EUI Univ.
 July 12, 2010


Virtual interface for multiple interfaces in a host
draft-hong-mif-virtual-interface-01

Abstract

The simultaneous usage of multiple interfaces in a host may cause the interface change. This document discusses how to solve the problems of interface change in a host and proposes a virtual interface which hides the change of network interface from the host IP stack to support simultaneous usage of multiple interfaces in a host.

Status of this Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.

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.”

This Internet-Draft will expire on January 13, 2011.

Copyright Notice

Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.



Table of Contents

1.  Introduction
2.  Introduction of a virtual interface
3.  Mechanism to use a virtual interface in a host
    3.1.  Architecture of a virtual interface in a host
    3.2.  Operations of a host with a virtual interface
4.  Security Considerations
5.  IANA Considerations
6.  Informative References
§  Authors' Addresses




 TOC 

1.  Introduction

In traditional TCP/IP network environments, a communication entity usually has a wire connection with a single network interface and it is fixed. As an introduction of wireless technologies and heterogeneous access technologies, a communication entity is able to move around between different access technologies networks and have multiple network interfaces [1] (Ernst, T., Montavont, N., Wakikawa, R., Ng, C., and K. Kuladinithi, “Motivations and Scenarios for Using Multiple Interfaces and Global Addresses, draft-ietf-monami6-multihoming-motivation-scenario-03,” May 2008.).

Because traditional network applications and TCP/IP stack are developed for a communication entity which has a single network interface, the adoption of multiple network interfaces into a general communication entity makes some problems. Because of the change of network interface during communication, there may be many considerations to support multiple interfaces in a host [2] (Blanchet, M. and P. Seite, “Multiple Interfaces Problem Statement, draft-ietf-mif-problem-statement-05 (work in progress),” July 2010.).

In order to solve the problems mentioned above, we propose a virtual interface scheme for a host with multiple network interfaces. We currently use a virtual interface to provide the duplication of network connections through multiple network interface cards on an important network node such as a server. With a virtual interface scheme, the host with multiple interfaces can operate as it has a single interface irrespective to the number of network interfaces [3] (Melia, T. and S. Gundavelli, “Logical Interface Support for multi-mode IP Hosts, draft-melia-netext-logical-interface-support-00 (work in progress),” July 2010.).



 TOC 

2.  Introduction of a virtual interface

In some operating systems such as Linux (or Unix), most network interfaces, such as eth0, wlan, and ppp, are associated to a physical and/or logical devices that are in charge of transmitting and receiving data packets. However, there are exceptions to this rule, and some logical network interfaces do not feature any physical packet transmission.

The virtual interface is not a real physical device and it is a logical network interface. It has connections with physical network devices within a network entity and the path between the virtual interface and real physical network devices is determined dynamically according to some policy.

The virtual interface is registered to the network layer and it is regarded as a general network interface. Then real physical interfaces are connected to the virtual interface. The network layer does not know the existence of these physical interfaces.

The virtual interface can be used for the duplication of network connections (the duplication of network interface cards) for fault tolerance or load sharing. If an important server has multiple physical network interface cards, it can survive even though one network interface card is down. It can keep a communication session with other live network interface cards. In this case, the presence of multiple network interface cards can be hidden to network layer and network layer regards the virtual inerface as a general network interface. The traditional network applications and network modules such as TCP/IP do not need to be modified to support multiple network interfaces in a host if a virtual interface is used.



 TOC 

3.  Mechanism to use a virtual interface in a host



 TOC 

3.1.  Architecture of a virtual interface in a host

In the following figure, network interfaces if_1, if_2 are real physical interfaces. The network interface VI is a virtual interface. The virtual interface is connected to the physical interfaces and it is shown to the network layer. In this figure, the network layer uses the virtual interface VI instead of physical interfaces if_1, if_2. To handle the virtual interface, the host needs a specific module (e.g., connection manager)to manage the virtual interface and select the path between the virtual interface and physical interfaces.




                  +-------------------------------+
                  |         Applications          |
                  |-------------------------------|
                  |        Transport area         |
                  |-------------------------------|
                  |         network area          |
                  |-------------------------------|
                  |      +------------------+   +------------+
                  |      | Virtual Interface|   | Connection |
                  |      |       (VI)       |   | Manager    |
                  |      +------------------+   +------------+
                  |           /        \          |
                  |          /          \         |
                  | +------------+ +------------+ |
                  | | Interface 1| | Interface 2| |
                  | |   (if_1)   | |   (if_2)   | |
                  | +------------+ +------------+ |
                  +-------------------------------+
 Figure 1: Architecture of a virtual interface in a host with two physical interfaces 



 TOC 

3.2.  Operations of a host with a virtual interface

When a network module in a host starts, the virtual interface is configured to send and receive packets. In Figure 1, if the host uses a physical interface if_1, the path between the virtual interface VI and the physical interface if_1 is configured.

When sending packets to another node, packets are delivered to the virtual interface and these packets are also forwarded into physical interface if_1 according to the path configuration. When receiving packets from another node, packets are delivered to if_1 and these packets are also forwarded into VI according to the path configuration.

If the host changes another interface due to movement of a host or the failure of network interface, the host chooses a physical interface if_2 and then makes the path between the virtual interface VI and the physical interface if_2. At this time, the connection manager updates the relation between a destination address and a network interface. When the host is sending packets to another node, packets are delivered to VI and these packets are forwarded into if_2 according to the path configuration. When the host is receiving packets from another node, packets are delivered to if_2 and these packets are also forwarded into VI according to the path configuration.



 TOC 

4.  Security Considerations

TBD



 TOC 

5.  IANA Considerations

This document has no actions for IANA.



 TOC 

6. Informative References

[1] Ernst, T., Montavont, N., Wakikawa, R., Ng, C., and K. Kuladinithi, “Motivations and Scenarios for Using Multiple Interfaces and Global Addresses, draft-ietf-monami6-multihoming-motivation-scenario-03,” May 2008.
[2] Blanchet, M. and P. Seite, “Multiple Interfaces Problem Statement, draft-ietf-mif-problem-statement-05 (work in progress),” July 2010.
[3] Melia, T. and S. Gundavelli, “Logical Interface Support for multi-mode IP Hosts, draft-melia-netext-logical-interface-support-00 (work in progress),” July 2010.


 TOC 

Authors' Addresses

  Yong-Geun Hong
  ETRI
  161 Gajeong-Dong Yuseung-Gu
  Daejeon, 305-700
  Korea
Phone:  +82 42 860 6557
Email:  yonggeun.hong@gmail.com
  
  Joo-Sang Youn
  DONG-EUI Univ.
  Busan,
  Korea
Phone:  +82 51 890 1993
Email:  joosang.youn@gmail.com