Internet Engineering Task Force F. Hu
Internet-Draft Z. Gu
Intended status: Standards Track L. Jin
Expires: January 26, 2011 ZTE Corporation
Jul 25, 2010
LISP Trans in MPLS Networks
draft-hu-lisp-mpls-trans-01.txt
Abstract
This document proposes an LISP trans solution in MPLS network,
provides a new LISP data encapsulation with two layer MPLS label and
simplifies the IP-in-IP encapsulation by cutting of the outer IP
header when LISP technology deploys in the MPLS network, the outer
label is used for data forwarding, and the inner label is used to
indicate the LISP data packet and carry the RLOC address information.
In additional, three deployment scenarios are provided in this
document..
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. LSP Signaling and Setup . . . . . . . . . . . . . . . . . . . 4
4. LISP label signaling and setup . . . . . . . . . . . . . . . . 4
5. MPLS label encapsulation format . . . . . . . . . . . . . . . 5
6. EID-RLOC-Label mapping . . . . . . . . . . . . . . . . . . . . 6
7. Deployment scenario . . . . . . . . . . . . . . . . . . . . . 6
7.1. Merging PE and xTR function . . . . . . . . . . . . . . . 6
7.1.1. Deployment description . . . . . . . . . . . . . . . . 6
7.1.2. Label-based forwarding . . . . . . . . . . . . . . . . 6
7.2. xTRs act as CE . . . . . . . . . . . . . . . . . . . . . . 8
7.3. Multihoming deployment . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative references . . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
It is common recognized that today's Internet routing and addressing
system is facing serious scaling problems, which is much discussed in
the Internet Architecture Board (IAB) workshop on Routing and
Addressing in Amsterdam. Several proposals have emerged after the
workshop. These proposals include LISP [LISP], are based on the idea
of "ID/Locator split".
LISP is a network-based ID/locator split solution, and needs a
mapping mechanism that allows mapping identifiers onto locators.
There are several mapping mechanisms, such as ALT [ALT], LISP-MS
[MS], and CONS [CONS], NERD [NERD], APT [APT], etc. The [ALT] and
[MS] solution is the recommendation mapping mechanism of LISP
workgroup. But the deployment of LISP needs further discussion.
This document specifics the deployment of LISP in MPLS network.
MPLS network is widely deployment in current network because of the
application of VPN service, traffic engineer, QoS etc., so it is
considered that the label-based switched technology can be used to
deployment the LISP technology.
This document specific an LISP trans solution when LISP deploys in
MPLS network, and provides a new data packet encapsulation format
that the out IP header of IP-in-IP encapsulation in LISP is cut off.
There are two layer MPLS label, the outer MPLS label is used to
forward LISP data packet in MPLS network, and the inner MPLS label
indicates the LISP data packet and carries the source RLOC address
information. The end-to-end MPLS technology can be implemented
between ITR and ETR. So the plenty of MPLS services, such as VPN
service, traffic engineer, QoS etc can be applied when deployed LISP.
There are three deployment scenarios provided in this document
according to the role of PE.
2. Terminology
Endpoint ID (EID): a 32-bit (for IPv4) or 128-bit (for IPv6) value
used in the source and destination address fields of the first (most
inner) LISP header of a packet. The host obtains a destination EID
the same way it obtains a destination address today, for example
through a DNS lookup or SIP exchange. Usually, the EID is an IP
address. If the host is required to support mobility, the EID should
be unique.
Routing Locator (RLOC): the IPv4 or IPv6 address of an egress tunnel
router (ETR). It is the output of an EID-to-RLOC mapping lookup.
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Label Switch Router (LSR): an MPLS node which is capable of
forwarding MPLS data packet based on the label forwarding table.
Label Edge Router (LER): an MPLS node that connects an MPLS domain
with a node which is outside of the domain, either because it does
not run MPLS, and/or because it is in a different domain. If an LSR
has a neighboring host which is not running MPLS, that that LSR is an
MPLS edge node.
Ingress Tunnel Router (ITR): a router which accepts an IP packet with
a single IP header (more precisely, an IP packet that does not
contain a LISP header). The router treats this "inner" IP
destination address as an EID and performs an EID-to-RLOC mapping
lookup through a mapping service. An ITR maintains a local mapping
table that stores some recently used EID-to-RLOC mapping. An ITR
also acts as the LER in MPLS network, it maintains a label forwarding
table. When ITR receives a data packet from its custom site, it does
an EID-to-RLOC mapping lookup, then does a label lookup through the
label forwarding table by the locator which is the result of EID-to-
RLOC mapping lookup.
Egress Tunnel Router (ETR): a router that accepts an IP packet where
the destination address in the "outer" IP header is one of its own
RLOCs. ETR also acts as the LER equipment and setups the point-to-
point LSP tunnel with the ITR. ETR distributes a inner label to its
peer ITR .
EID-to-RLOC mapping: a binding between an EID and the RLOC-set that
can be used to reach the EID. An RLOC-set may contain multiple RLOC,
and perhaps the preference to an RLOC.
3. LSP Signaling and Setup
ITR and ETR act as LER in MPLS network, and there is a point to point
LSP tunnel between ITR and ETR. The LSP tunnel is established by the
signal protocol, such as LDP, RSVP. If ITR and ETR belong to
different AS, the LSP tunnel is an inter-As tunnel. The LISP data
packets are forwarded along the LSP tunnel. The LSP should be setup
between ITR and ETR before requesting EID-to-RLOC mapping and
performing customer packet forwarding.
4. LISP label signaling and setup
It is required for ETR to identify the MPLS packet which encapsulates
LISP type packet, and identify the source RLOC of the LISP packet.
For this purpose, there is an inner MPLS label between outer MPLS
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label and LISP header to identify the LISP data packet. When the
LISP data packet with label encapsulation reaches the ETR, ETR strips
the MPLS label and gets the LISP data with LISP header, and ETR
couldn't deal with the data packet if there is no inner label to
identify the LISP header.
The inner MPLS label could be distributed by MP-BGP protocol. The AF
(address family) of MP-BGP protocol should be extended to support
inner label distribution function in LER (ITR and ETR). The LISP
label will be distributed among ITR and ETR when the LISP function is
enabled in the peer of ITR and ETR.
5. MPLS label encapsulation format
The left figure shows the IP-in-IP encapsulation. The source and
destination IP address of outer IP header are RLOC address, and the
source and destination IP address of inner IP header are EID address.
This document proposes a MPLS label encapsulation to encapsulate the
LISP data packet, as shows in the right figure. There are two layer
labels, the outer label is used for data forwarding, and the inner
label identifies the LISP packet. The outer label is distributed by
the signal protocol, and the inner label is distributed by extension
MP-BGP protocol. The UDP header is cut off in the optimal
encapsulation format, and the LISP data checksum can be done by CRC
field of layer 2 header.
MPLS label encapsulation format
+-----------+ +----------+
+ outer + + label +
+ IP Header + + +
+-----------+ +----------+
+ UDP + + label +
+-----------+ +----------+
+ LISP + + LISP +
+-----------+ +----------+
+ Inner + + Inner +
+ IP Header + + IP Header+
+-----------+ +----------+
IP-in-IP encapsulation MPLS Label encapsulation
Figure 1
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6. EID-RLOC-Label mapping
EID-to-RLOC mapping is established by the mapping mechanism, such as
ALT, LISP-MS. And there is a cache in ITR to record and store the
recently EID-to-RLOC record. ITR and ETR belong to the MPLS domain,
and there is label binding to the RLOC address, so the binding of
RLOC and label is stored in the ITR.
When there is data packet (whether IPv4 data packet or IPv6 data
packet), ITR search the RLOC address in the EID-to-RLOC cache
according to the EID address, then search the label forwarding table
to get the outer label of RLOC address. The inner MPLS label is
distributed according to the LISP-RD, which carries the information
of RLOC address. The ETR distributes different inner label to
different ITR. When data packet reaches ETR, ETR can get the RLOC
address information according to the inner label.
The original data packet will be encapsulated with an LISP header,
inner MPLS label and outer MPLS label according to the figure 1.
7. Deployment scenario
7.1. Merging PE and xTR function
7.1.1. Deployment description
There are three deployment scenarios provided in this document
according to the role of MPLS PE. The first scenario is that MPLS PE
acts as xTR, that is, the ingress PE acts as ITR and egress PE acts
as ETR. ITR not only stores and maintains the EID-RLOC mapping in
the cache, but also sets up the RLOC and outer label binding, and
maintains the label forwarding table. Point-to-point LSP tunnel is
established for LISP data forwarding between ITR and ETR by using the
current signaling protocol, such as LDP, RSVP etc. The data
encapsulation can be optimal as MPLS label encapsulation format in
figure 1.
7.1.2. Label-based forwarding
The LISP data packet in MPLS network will be encapsulated by MPLS
label, and there is only one layer IP header, and the IP address of
the IP header is EID address. The LISP data packet forwards
according to the outer MPLS label.
The following is the example of data forwarding process. The figure
2 is the network architecture, and it is supposed that host A belongs
to site A and host B belongs to site B, and host A will communicate
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with host B.
(1) Host A sends an IP packet (a IPv4 packet or IPv6 packet,
whatever) to its default ITR. The destination IP address and source
IP address of the IP packet are the EID address of host B and host A
respectively;
(2) When ITR receives the IP packet, it looks up the RLOC of the EID
address of host B in the local cache. If it finds the RLOC, it means
that the packet is not the first packet, then continue to look up the
out label of RLOC address, if it does, then skips into step 6
indirectly; if there is no match RLOC address of EID, it means that
the data packet is the first packet, then go on with step 3;
(3) ITR encapsulates the LISP-Request message and sends to the
mapping system for requesting the RLOC of EID2;
(4) When the mapping system receives LISP-Request, it looks up the
RLOC in the mapping database and response the LISP-reply message with
the right RLOC address;
(5) When ITR receives the LISP-Reply message, it stores the EID-to-
RLC mapping into its local cache, and then look up the point-to-point
LSP tunnel between ITR and ETR. Note, the point-to-point LSP tunnel
between ITR and ETR should be already setup before requesting RLOC of
EID2;
(6) ITR prepends LISP data packet with label encapsulation as figure
1. The destination and source IP address of inner IP header are EID
address of host A and host B respectively, then ITR sends the data
encapsulated to the MPLS network. The data packet forwards with
label switched;
(7) When the LISP data packet reaches the ETR, it strips the label
and gets the original IP packet. Usually, the outer label is poped
in the penultimate MPLS node, and ETR only lookup the inner label and
gets the RLOC address information of ITR;
(8) The IP packet forwards to the destination host B through site B
according to the EID address of host B.
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label-based forwarding
+-------+ +--------+ +-----+ +--------+ +--------+
|site A CE---+ITR/LER +---+ LSR +---+ETR/LER +--CE site B|
+-------+ +--------+ +-----+ +--------+ +--------+
MPLS Domain
-------------------------------
Figure 2
7.2. xTRs act as CE
The second scenario is the common traditional deployment solution.
xTRs is the exit router which is located in the edge of customer
network. Form the view of MPLS network. xTR acts as CE. ITR does
the LISP format with IP-in-IP encapsulation and doesn!_t run MPLS
technology, and PE does the traditional MPLS encapsulation, which is
similar with the MPLS BGP VPN.
The data encapsulation in PE is as following figure. There are MPLS
label and IP-in-IP encapsulation. The outer source and destination
IP address are the RLOC address of ITR and ETR respectively. The
MPLS label is distributed according to the RLOC address of PE, and it
used for data forwarding in the MPLS domain.
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label encapsulation format
+-----------+
+ out +
+ label +
+-----------+
+ inner +
+ lable +
+-----------+
+ outer +
+ IP Header +
+-----------+
+ UDP +
+-----------+
+ LISP +
+-----------+
+ Inner +
+ IP Header +
+-----------+
Figure 3
7.3. Multihoming deployment
The third scenario is a multihoming deployment solution. xTR locates
in the custom site. ITR acts as the CE and multihomes to two or
several PEs, such as PE1 and PE3 in the following figure. ITR does
the LISP data encapsulation .ETR runs MPLS technology. The core
network is MPLS network and the data packet forwards based on MPLS
Label. ETR and PE1 establish the MP-BGP peer and take use of the
inter-AS option B to distribute inner label from ETR to PE1. The
outer label is distributed in MPLS domain. It is configured the
static route from ITR to PE1 and PE3.
multihoming deployment
+----------+ +-------+ +-----+ +--------+ +-------------+
|site A CE +--+ITR1/PE1 +---+ p +---+ ASBR1 +---ETR1/PE2 site B|
+----------+ | +-------+ +-----+ +--------+ +-------------+
|
|
| +-------+ +-----+ +--------+ +-------------+
+-+ITR2/PE3+---+ p +---+ ASBR2 +---ETR2/PE4 site C|
+-------+ +-----+ +--------+ +-------------+
Figure 4
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8. Security Considerations
9. Acknowledgement
10. References
10.1. Normative references
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB
Workshop on Routing and Addressing", RFC 4984,
September 2007.
10.2. Informative References
[ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP
Alternative Topology (LISP-ALT)",
draft-ietf-lisp-alt-02.txt (work in progress), Jan 2010.
[APT] Jen, D., Meisel, M., Massey, D., Wang, L., Zhang, B., and
L. Zhang, "APT: A Practical Transit Mapping Service",
draft-jen-apt-01.txt (work in progress), November 2007.
[CONS] Brim, B., Chiappa, N., Farinacci, D., Fuller, V., Lewis,
D., and D. Meyer, "LISP-CONS:A Content distribution
Overlay Network Service for LISP",
draft-meyer-lisp-cons-04.txt (work in progress),
April 2008.
[LISP] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis,
"Locator/ID Separation Protocol (LISP)",
draft-ietf-lisp-00.txt (work in progress), March 2010.
[MS] Farinacci, D. and V. Fuller, "LISP Map Server (LISP)",
draft-ietf-lisp-ms-04.txt (work in progress), Oct 2009.
[NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database",
draft-lear-lisp-nerd-07.txt (work in progress), Jan 2010.
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Authors' Addresses
Fangwei Hu
ZTE Corporation
889 Bibo Road
Shanghai 201203
China
Phone: +86-21-68896273
Email: hu.fangwei@zte.com.cn
Zhongyu Gu
ZTE Corporation
68 Zijinghua Road
Nanjing 200012
China
Phone: +86-25-52872044
Email: gu.zhongyu@zte.com.cn
Lizhong Jin
ZTE Corporation
889 Bibo Road
Shanghai 201203
China
Phone: +86-21-68896273
Email: lizhong.jin@zte.com.cn
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