Internet DRAFT - draft-zhang-lisp-hmm
draft-zhang-lisp-hmm
Network Working Group Hongke Zhang
Internet Draft Feng Qiu
Expires: June 2013 Huachun Zhou
Xiaoqian Li
Li Yi
Ying Rao
Zhengxin Zhang
December 17, 2012
A Hierarchical Mobility Management in LISP network
draft-zhang-lisp-hmm-01.txt
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Abstract
This draft proposes a Hierarchical Mobility Management (HMM) in
Locator/ID Separation Protocol (LISP) networks. The Internet is
divided into a number of mapping domains (MDs). An Agent Tunnel
Router (ATR) as an agent of each MD manages the Mobile Node's EID-to-
RLOC mapping. For the movement within the MD, the ATR keeps the EID-
to-RLOC mapping invariable, so it avoids the mapping update in the
mapping system and the Tunnel Router (TR) of each correspondent node.
For the handover between different MDs, to support fast update and
handover, a united mapping table is proposed in the ATR.
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].
Table of Contents
1. Introduction ................................................ 2
2. Definition of items ......................................... 3
3. HMM Overview ................................................ 4
3.1. The architecture of HMM................................. 4
3.2. Micro-Mobility ......................................... 5
3.3. Macro-Mobility ......................................... 7
4. Mapping Table ............................................... 9
5. Properties ................................................. 11
6. Security Considerations..................................... 12
7. IANA Considerations ........................................ 12
8. References ................................................. 13
Author's Addresses ............................................ 13
Acknowledgment ................................................ 14
1. Introduction
In the current TCP/IP stack, IP address is overloaded with the
semantics of both host identifiers and locators [RFC 4984]. From the
application layer of view, IP address identifies a host and it is
used in the application and transport layer. From the network layer
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of view, IP address indicates the current topological location of a
host. The dual roles of IP address make it difficult to support
mobility. When a host moves into a new subnet, it must configure a
new IP address. As the transport layer connection identifier includes
IP address, the host has to re-establish connections. Thus, to keep
connections alive, we need to decouple the dual roles of IP address.
We propose a novel mobility management based on the LISP networks
[LISP]. A mapping system as a separate logical management plane
controls the MN's EID-to-RLOC mapping so as to offer good
manageability. In addition, the ATR as an indirection point takes
charge of mapping EIDs to RLOCs which can hide the MN and network
equipment's location and achieve location privacy. In addition, this
is a network-based mobility management protocol, which does not
require MNs to participate in any mobility-related signaling, so it
avoids a few signaling cost in wireless links.
Due to the introduction of identifier/locator separation, a critical
challenge is how to keep the mapping between the MN's identifier and
its dynamically changing IP address [Mapping, SMGI]. This implies
that the mapping system and the TR of each correspondent node (CN)
need to update the EID-to-RLOC mapping when the MN moves. To reduce
the update signaling cost, we distinguish micro-mobility and macro-
mobility by introducing an ATR in each mapping domain. For micro-
mobility, the ATR as a special TR keeps the MN's identifier-to-
locator mapping invariable and does not need to update the mapping in
the mapping system and the TR of each CN. To perform the fast mapping
update in the case of macro-mobility, we design a united mapping
table in the ATR. It contains mapping information of each CN which
the MN is communicating with so that the old ATR can directly inform
the new ATR mapping entries of CNs. In this way, the new ATR does not
need to query mapping servers, which eliminates the mapping request
delay.
2. Definition of items
Endpoint ID (EID): An EID is 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. An EID is allocated to
a host from an EID-prefix block associated with the site where the
host is located. See [LISP] for details.
Routing Locator (RLOC): A RLOC is an IPv4 or IPv6 address of an
egress tunnel router (ETR). A RLOC is the output of an EID-to-RLOC
mapping lookup. An EID maps to one or more RLOCs. Typically, RLOCs
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are numbered based on the connectivity of provider networks. See
[LISP] for details.
EID-to-RLOC mapping: a binding between an EID or EID-prefix and a
RLOC set which can be used to reach the EID. The xTRs can
encapsulate packets with the RLOC in the EID-to-RLOC mapping to
reach the destination EID. A RLOC set may contain multiple RLOCs to
perform multihoming or traffic engineering.
Mapping Server (MS): A network infrastructure component which stores
the EID-to-RLOC mappings and responds to Map-Requests.
Mapping Domain (MD): The Internet is divided into a number of mapping
domains (MDs) and each MD consists of a MS and several xTRs.
Agent Tunnel Router(ATR): An ATR has two functionality of ITR and ETR,
which can encapsulate and decapsulate packets. For the movement
within the MD, the ATR keeps the EID-to-RLOC mapping invariable.
The ATR receives IP packets from TRs on one side and sends LISP-
encapsulated IP packets toward the Internet on the other side.
Meanwhile, an ATR receives LISP-encapsulated IP packets from the
Internet on one side and sends decapsulated IP packets to TRs or
hosts on the other side. In addition, it sends a Map-request to the
mapping system when it does not have the EID-to-RLOC mapping for
the destination EID.
Tunnel Router(TR): A TR encapsulates packets with a tunnel header and
sends them to the ATR by a tunnel.
3. HMM Overview
3.1. The architecture of HMM
Figure 1 shows the network architecture of HMM, which contains two
hierarchies: a mapping system and the current Internet. The mapping
system is an overlay network on the top of Internet and consists of a
set of mapping servers (MS). MSs manage EID-to-RLOC mapping entries
and resolve Map-Request messages. There have been several proposals
to discuss the architecture of the mapping system [LISP-DHT] [LISP-
TREE] [LISP+ALT].
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The Internet is divided into a number of MDs. Each MD contains
several TRs. Any TR may be as an agent to manage the movement of MNs
within its MD. The agent TR encapsulates packets with RLOCs and
maintains the mappings between EIDs and RLOCs. Assume the first TR
that an MN attaches to in the MD is the ATR. When the MN connects to
other TRs in the same MD, the TR will establish a tunnel with the ATR.
+-------------------------------------------------+
| Mapping +----+ +----+ |
| System | MS |------------ | MS | |
| +----+ +----+ |
| | | |
| | | |
| +----+ +----+ |
| | MS |------------ | MS | |
| +----+ +----+ |
| / \ |
| ----------/----------------------\------------- |
| MD1 / | MD2 \ |
| +---+ | +---+ |
| /|TR |\ | /|TR |\ |
| / +---+ \ | / +---+ \ |
| / | | \ | / | | \ |
| / | | \ | / | | \ |
| +---+ | | +---+ | +---+ | | +---+ |
| |TR |---/---\---|TR | | |TR |---/---\--- |TR | |
| +---+ / \ +---+ | +---+ / \ +---+ |
| | / \ | | | / \ | |
| | +---+ +---+ | | | +---+ +---+ | |
| --|TR1|----|TR2|-- | --|TR3|----|TR4|-- |
| +---+ +---+ | +---+ +---+ |
| | |
+-------------------------------------------------+
Figure 1
:Architecture of HMM
3.2. Micro-Mobility
We divide the global internet into a number of MDs and assume each
autonomous system (AS) is a MD, which is managed by different
Internet Service Providers (ISP). When an MN moves within the same MD,
we define it micro-mobility. While the MN moves between different MDs,
we call it macro-mobility. We deal with macro-mobility and micro-
mobility separately to minimize the signaling cost and alleviate the
burden of the mapping system.
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Figure 2 illustrates the message flows for the location management
scheme in micro-mobility scenario. First of all, an MN attaches the
TR1, and then the TR1 is the agent of the MN in this MD. The ATR1
sends a Map-Register message including the EID and RLOC of the MN to
the associated MS. The MS adds the mapping entry of the MN.
When a CN wants to communicate with the MN, it sends packets to the
ATR3 using its and the MN's EID as packets'source address and
destination address. The ATR3 will send a LISP Map-Request message to
the MS. The MS lookups the destination EID of the Map-Request and
matches it against the prefixes in the EID-to-RLOC mapping database.
If there is no match, the Map-Request is dropped. Otherwise, a LISP
Map-Reply is returned to the ATR3. The ATR3 encapsulates packets with
ATR3's RLOCs and ATR1's RLOCs as packets'source address and
destination address. When the ATR1receives these packets, it
decapsulates packets and then sends them to the MN.
When the MN moves into the TR2 coverage area with the same MD of the
ATR1, the TR2 only sends one Map-Update message to the ATR1. The ATR1
responds to the Map-Update message and establishes a tunnel with the
TR2. In this case, we regard the ATR1 as a local agent of the MN. As
long as the MN still stays in this MD, the MN's EID-to-RLOC mapping
does not change. All the packets from other MDs destination to the MN
pass through the ATR1 and then the ATR1 forwards packets to the TR2
by the tunnel. In this way, the mapping information in the remote
ATR3 and the MS need not be changed, so this scheme significantly
reduces signaling cost.
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+--+ +---+ +----+ +--+ +----+ +---+
|MN| |TR2| |ATR1| |MS| |ATR3| |CN |
+--+ +---+ +----+ +--+ +----+ +---+
|<------Attachment-----> | | | |
| | | Map- | | |
| | |-Register->| | |
| | | | Map- |<=Packets= |
| | | |<--Request- | |
| | | | | |
| | | |-Map-Reply->| |
| | | | | |
| | |<========Packets========| |
|<========Packets======= | | | |
| | | | | |
|<Attachment>| | | | |
| | Map- | | | |
| |-Update--> | | | |
| | | | | |
| |Map-Update | | | |
| |<-Response | | | |
| | | | | |
| | |<=======Packets======== |<=Packets= |
| |<=Packets= | | | |
| <=Packets= | | | | |
| | | | | |
Figure 2:
Message flows of the location management scheme
in micro-mobility scenario
3.3. Macro-Mobility
Macro-mobility indicates that an MN crosses different MDs. In this
case, the stale mapping entry in the mapping system and the TR of
each CN must be updated in order to help new initiators and ongoing
communication users acquire the correct mapping information.
Figure 3 shows the mobility management scheme in macro-mobility
scenario. Assume that the MN has performed the handover from the ATR1
to the TR2 as shown in Fig. 2. Then, the MN moves from the TR2 in the
MD1 to the TR4 in the MD2. The TR4 as an agent in the MD2 adds the
MN's mapping entry in its local table and then sends a Map-Register
message to the MS.
In addition, the ATR4 sends a Map-Update message to the ATR1. Then,
the ATR1 sends a Map-Update response message to notify mapping
entries of CNs to the ATR4. In this way, the ATR4 can acquire a set
of CNs'mapping information. It avoids sending more messages to the
mapping system, so this solution reduces the signaling cost. As soon
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as the ATR4 obtains the CNs'mappings, it will directly encapsulate
and forward packets, so the scheme can support fast handoff.
After that, the ATR1 sends a message to the ATR3 in order to update
the new MN's mapping information in the ATR3's mapping table. Once
the ATR3 gets the new mapping, packets destination to the MN are
directly routed to the ATR4, while do not need to pass though the old
ATR1. Thus, the scheme can avoid triangle routing and achieve route
optimization. Finally, the ATR1 removes the MN's mapping entry from
its mapping table.
In addition, the ATR1 sends a delete tunnel message to the TR2 and
macro-mobility's operations complete.
+--+ +---+ +----+ +----+ +--+ +----+ +---+
|MN| |TR2| |ATR1| |ATR4| |MS| |ATR3| |CN |
+--+ +---+ +----+ +----+ +--+ +----+ +---+
|<---------Attachment-------> | | | |
| | | | Map- | | |
| | | |-Register->| | |
| | | | | | |
| | | Map- | | | |
| | |<-Update- | | | |
| | | | | | |
| | |Map-Update| | | |
| | |<-Response| | | |
| | | | | | |
| | | | | | |
| | |---------- Update-Map----------> | |
| | |<------ Update-Map Response----- | |
| | | | | | |
| | Delete | | | | |
| |<-Tunnel- | | | | |
| | | | | | |
| | Delete | | | | |
| |<-Tunnel- | | | | |
| | Response | | | | |
| | | | | | |
| | | | | |<==Packets=|
| | | | <=====Packets======= | |
|<=========Packets=========== | | | |
| | | | | | |
Figure 3:Message flows of the location management scheme
in macro-mobility scenario
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4. Mapping Table
The LISP proposes a kind of separate mapping table in the TR. The
mapping information of local nodes and remote nodes stores in the
EID-to-RLOC Database and the EID-to-RLOC Cache, respectively. The
local table maintains the EID-to-RLOC mappings for the EID prefixes
"behind" the router. The EID-to-RLOC Cache stores mapping entries of
CNs which local users are communicating with.
In this solution, the EID-to-RLOC Cache is shared by all the MNs. If
an MN attaches another mapping domain's TR, the mapping information
in the TR of each CN need be updated. However, all the MNs share the
same cache and the old ATR does not know which CN is communicating
with the MN. Thus, the old ATR can not inform the new ATR of CNs'
mapping information. The new ATR must send mapping request messages
to the mapping system. It not only adds query delay but also brings
excess signaling cost.
For macro-mobility scenario, to support fast handover and reduce the
overload of the mapping system, we design a united mapping table in
the ATR integrating the mappings of local MNs with the mapping
entries of CNs. Figure 4 illustrates the data structure of the
mapping table. Each mapping entry contains a local MN and a list of
CNs which the local MN is communicating with.
When an MN attaches to another MD's TR, the old ATR lookups the
united mapping table to find the list of CNs of the MN. After that,
the old ATR sends these mappings of CNs to the new domain's ATR. In
this way, the new ATR can acquire mapping information quickly and
accurately.
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+----------------------------------------------------------+
Local | EID | RLOC |Flag |Tunnel Source |Tunnel destination|Timer|
Node | | | | address | address | |--
+----------------------------------------------------------+ |
-----------------------------------------------------------
| +----------------------------- +
|--> | EID | RLOC | Timer |
-------------------------------
A list | EID | RLOC | Timer |
of CNs +------------------------------
:
:
-------------------------------
| EID | RLOC | Timer |
+----------------------------- +
Figure 4: The mapping table in the ATR
As shown in Fig. 4, the local node's mapping information in the
united mapping table contains six sections. "EID"is used to
represent the identity of an MN. "RLOC"is the IP address of the ATR
for locating nodes in the network topology. "Flag"indicates the
location of the MN. If the value of "Flag"is "LEFT", it indicates
that the MN has left the ATR and the ATR forwards packets by the
tunnel. "Tunnel source address"and "Tunnel destination address"are
used to establish a tunnel and encapsulate packets with the tunnel
header for the MN. If the value of "Flag"is "LIVE", it indicates the
MN still is in the MD of the ATR. The function of "Timer"is to
manage the MN's mapping entry. Mapping entries in the mapping table
will not be deleted until the value of "Timer"is zero that hints the
MN leaves the ATR coverage area.
In addition, the united mapping table in the ATR also includes a list
of CNs. Each CN's entry consists of "EID", "RLOC"and "Timer". "EID"
and "RLOC"are identity and location of a CN. The ATR maintains a
"Timer"for each CN's mapping entry. Whenever packets pass through
the ATR, the timer resets to maximum. If the lifetime is expired, the
ATR will remove the CN's mapping entry from the mapping table.
+-----------------------------------------------------+
Local | EID | Tunnel Source | Tunnel destination| Timer|
Node | | address | address | |
+-----------------------------------------------------+
Figure 5: The mapping table in the TR
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Figure 5 illustrates the mapping information in the TR. "EID"is the
identity of an MN. "Tunnel source address"and "Tunnel destination
address"are used to set up a tunnel. "Tunnel source address"is an
IP address of the TR and "Tunnel destination address"is one of the
ATR's addresses. "Timer"is used to send a keeplive message to the MN
in order to confirm that the MN still is its area. When "Timer"
exceeds a predetermined threshold, the TR sends message to the MN. If
the TR receives the response message from the MN, the TR resets the
"Timer"to zero. Otherwise, the TR considers that the MN has been
left from its area.
5. Properties
In this section, we describe properties of the mobility management
scheme based on identifier locator split architecture. The proposed
scheme exhibits the following several advantages.
Connection Survivability: The novel scheme must allow an MN to roam
while keeping transport connections alive. By means of the identifier
locator separation scheme the current IP address is split into two
spaces for end-systems identifiers and routing locators. When an MN
attaches a new access point, it only changes its locator. Because
the identifier of the MN is constant and the locator's change is
transparent to the upper layer, which makes it possible to keep
transport connections alive. Therefore, the identifier/locator
separation solution can support global roaming seamless and fast
handover.
Location Privacy: In the proposed identifier/locator separation
scheme, if a CN wants to communicate with a MN, it uses its and MN's
identifier as the data packets'source and destination address. And
then the ATR receives the data and encapsulates them with locators.
The core network's routers forward the data packets to the ATR of the
MN according to the locator. The MN's ATR decapsulates the data
packets and forwards them to the TR that the MN attaches. Finally,
the TR sends packets to the MN. By the identifier/locator separation
scheme, the CN only knows MN's identifier, so the location of the MN
is hidden from the CN.
Support routing scalability: One main aim of identifier/locator
separation is to support routing scalability. The identifier/locator
separation scheme removes host's identifier entries from core routers
in today's routing system, without losing reachability to any
destinations. After packets which are sent by a host arrive at a TR,
they are encapsulated with the locator. Since the locator is
reachable in core routers, the packet can be forward to destination.
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We design a novel mobility management scheme based on the
identifier/locator separation which does not damage the separation
architecture and can solve both global routing scalability problems
and mobility support. As a result, the proposed mobility management
scheme based on identifier/locator separation can support routing
scalability.
6. Security Considerations
TBD
7. IANA Considerations
This document makes no request of the IANA.
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8. References
[RFC 4984] David, M., Lixia, Z. and Kevin, F., "Report from the IAB
Workshop on Routing and Addressing," RFC 4984, September 2007.
[LISP] Dino, F., Vince, F., Dave, M. and Darrel, L., "Locator/ID
Separation Protocol (LISP)", draft-ietf-lisp-24.txt(work in progress),
November 2012.
[Mapping] Jen, D., Zhang, L., "Understand mapping", draft-jen-
mapping-00.txt, 2009.
[SMGI] Zhang, L., Wakikawa, R., Zhu, Z., "Support Mobility in the
Global Internet", In proceedings of the 1st ACM workshop on Mobile
internet through cellular networks, 2009.
[LISP-DHT] Laurent, M. and Luigi, I., "LISP-DHT: Towards a DHT to
map identifiers onto locators", in Proc of ReArch'08, December 2008.
[LISP-TREE] Lorand, J., Albert, C-A., Florin, C., Damien, S. and
Oliver, B., "LISP-TREE: A DNS Hierarchy to Support the LISP Mapping
System", IEEE Journal on Selected Areas in Communication, VOL. 28,
NO.8, October 2010.
[LISP+ALT] Vince, F., Dino, F., Dave, M. and Darrel, L., "LISP
alternative topology (LISP-ALT)", draft-fuller-lisp-alt-10.txt(work
in progress), December 2011.
Author's Addresses
Hongke Zhang, Feng Qiu, Huachun Zhou, Xiaoqian Li, Li Yi, Ying Rao
National Engineering Laboratory for Next Generation Internet
Interconnection Devices
School of Electronics and Information Engineering
Beijing Jiaotong University of China
Phone: +86 01051685677
hkzhang@bjtu.edu.cn
07111019@bjtu.edu.cn
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hczhou@bjtu.edu.cn
xiaoqianli@bjtu.edu.cn
10111022@bjtu.edu.cn
11111028@bjtu.edu.cn
Zhengxin Zhang
BEIJING C&W ELECTRONICS(GROUP) CO.,LTD.
paulzhang@163.com
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
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