Network Working Group J. Wu
Internet-Draft C. Liu
Intended status: Standards Track Tsinghua University
Expires: August 18, 2014 February 14, 2014
Communication between Softwire CEs with shared addresses
draft-liu-softwire-ce-comm-shared-addr-00
Abstract
In some Softwire mechanisms, multiple Customer Edge (CE) devices can
share the same IPv4 address by using different port sets. This
document describes a problem of the IPv4 communication between
Softwire CEs with the same IPv4 address.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 2
4. CE Behavior . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
IPv4 devices use IPv4 addresses to recognize their local addresses.
In many implementations (e.g. Linux), when an IPv4 device is
forwarding or directly sending a packet, if the IPv4 destination
address of the packet is one of the local addresses of the device,
the device will never send the packet out. The device is usually
pre-configured with local routing records to route all packets
destined to local addresses into local loopback interface.
Softwire mechanisms, such as MAP-E [I-D.ietf-softwire-map] and
Lightweight 4over6 [I-D.ietf-softwire-lw4over6], make use of address
+ port set based IPv4 address sharing. Multiple Softwire CE devices
(e.g. MAP CE and lwB4) are configured with the same IPv4 address,
each with a different port set.
When a CE attempts to send IPv4 packets to another CE and both CEs
are configured with the same IPv4 address but different port sets,
the IPv4 packets may be consumed by the first CE. This problem
causes the CEs with the same IPv4 address failed to send IPv4 packets
to each other. This document describes this problem and requires
port set enabled devices to use IPv4 address + port set to recognize
their local addresses.
2. Requirements Language
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 [RFC2119].
3. Problem Statement
When an IPv4 device sends a packet, if the destination address of the
packet is one of the local IPv4 addresses of the device, the packet
is consumed by the device itself and will not be sent out of the
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device. When the device is upgraded to support port set, it is
configured with port-restricted IPv4 address(es). The same IPv4
address may be allocated to multiple devices. If the device still
use IPv4 address to recognize its local address, it is unable for the
device to send IPv4 packets to any other devices that are configured
with the same IPv4 address and a different port set.
Figure 1 shows an example scenario of the problem. In Figure 1(a),
two hosts work as Softwire CEs. They are provisioned with the same
IPv4 address 198.51.100.1, each with a different port set. When
host1 sends a packet to host2 with the destination address
198.51.100.1 and destination port 3000, its forwarding engine
recognizes that 198.51.100.1 is its local address, so the packet is
forwarded into its loopback interface. In Figure 1(b), two CPEs work
as Softwire CEs and each connects to an IPv4 host. When host3 sends
a packet to host4 with the destination address 198.51.100.2 and
destination port 3001, the packet is forwarded to CPE1. After
received the packet, CPE1 recognizes that the destination address
198.51.100.2 is its local address, so the packet is consumed by CPE1
and never forwarded to CPE2/host4.
dst=198.51.100.1,port 3000
+----+.........X.............
| | .
| v v
+--------+ +--------+
|Softwire| Softwire |Softwire|
| host1 +--+...........+--+ host2 |
+--------+ +--------+
198.51.100.1 198.51.100.1
port 1024-2047 port 2048-4095
(a) Host as CE
dst=198.51.100.2,port 3001
+--------------+..............X............
| | .
| v v
+-------+ +---------+ +---------+ +-------+
| IPv4 | |Softwire | Softwire |Softwire | | IPv4 |
| host3 +-----+ CPE1 +--+...........+--+ CPE2 +-----+ host4 |
+-------+ +---------+ +---------+ +-------+
198.51.100.2 198.51.100.2
port 1024-2047 port 2048-4095
(b) CPE as CE
Figure 1: An Example of the Problem
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4. CE Behavior
A Softwire CE, that supports port set based IPv4 address sharing,
MUST use IPv4 address + port set to recognize its local address.
When forwarding an IPv4 packet, if the destination address of the
packet is the CE's IPv4 address but the destination port of the
packet does not belong to the port set of the CE, the CE MUST NOT
send the packet into its local loopback interface. The packet should
be sent to CE's tunnel virtual interface or WAN interface, as per the
forwarding policy of the corresponding Softwire mechanism.
5. Security Considerations
TBD
6. IANA Considerations
This document does not include an IANA request.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[I-D.ietf-softwire-lw4over6]
Cui, Y., Qiong, Q., Boucadair, M., Tsou, T., Lee, Y., and
I. Farrer, "Lightweight 4over6: An Extension to the DS-
Lite Architecture", draft-ietf-softwire-lw4over6-06 (work
in progress), February 2014.
[I-D.ietf-softwire-map]
Troan, O., Dec, W., Li, X., Bao, C., Matsushima, S.,
Murakami, T., and T. Taylor, "Mapping of Address and Port
with Encapsulation (MAP)", draft-ietf-softwire-map-10
(work in progress), January 2014.
Authors' Addresses
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Jianping Wu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-6278-5983
Email: jianping@cernet.edu.cn
Cong Liu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-6278-5822
Email: gnocuil@gmail.com
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