COM555: Mobile Technologies

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COM555 Mobile Technologies

• Location-Identifier Separation

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• In the current Internet TCP/IP Protocol Stack,
  the IP address functions
• simultaneously as
• A Routing Locator (an identifier with a
  topological meaning)
• and
• An Endpoint Identifier

Application Layer
IP-address,, port (Endpoint Identifier)
Transport Layer
IP-address (Routing Locator)
Internet Layer
Data Link Layer
Physical Layer
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Location-Identifier Separation

• When a host changes its point of attachment to
  the Internet, its IP address must change as well
• Therefore all transport sessions will break
• There have been various workarounds to
  implement mobility on the Internet

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Location-Identifier Separation

• More fundamental approaches aim to separate
  Routing Locators and Endpoint Identifiers to
  remove all identification related functionality
  from topology related information such as IP
  addresses.
• Current implementations adopt IP as the
  communications endpoint.
• New approaches have become known as
  Location-Identifier (L.I.) Separation.

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Location-Identifier Separation

• These more fundamental approaches require the
  redesign of the Internet protocol stack
• Such proposals are, by definition radical, and
  will be difficult to implement.
• (Recall IPv4 vs Ipv6)
• The ideas have emerged from the Routing Research
  Group (RRG) of the Internet Research Task Force
  (IRTF)

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L.I Separation

• The lack of L.I. Separation causes problems
  beyond simply mobility
• A key issue is user location privacy
• When
• Identifiers are long lived, and
• A publicly available mapping exists between
  identifiers and locators,
• it is possible to determine the location of a
  host and thus, the user using it
• Without the users permission, or knowledge

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Privacy

• Invasion of privacy is increasingly becoming a
  criminal offence!
• It is important that new mechanisms, by default,
  do not reveal the location of a particular host
  to unknown observers.

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Proposed Solutions

• Four proposed solutions have exercised the RRG
• The Host Identity Protocol (HIP)
• Network Address Translation for IPv6 to IPv6
  (NAT66)
• Identifier-Locator Network Protocol (ILNP)
• Location-Identifier Separation Protocol- Mobile
  Node (LISP-MN)

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Fundamental Approaches to Location-Identifier
Separation

• Most approaches to LI Separation fall into two
  broad categories
• Those that introduce an extra layer to hold the
  original endpoint identifiers
• Those that split the IPv6 address space into a
  part that has topological meaning, and a part
  that is used to identify the host.

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Case Study

• All four approaches have their advocates and
  detractors.
• None of them are perfect.
• All are work in progress
• We will briefly review LISP-MN as this has gained
  significant industrial support in recent years.

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Location-Identifier Separation Protocol Mobile
Node (LISP-MN)

• The LISP-NM Protocol enables a mobile node to
  roam across network whilst retaining its IP
  address.
• During hand-off, sessions may pause, and some
  data loss is possible.
• The key issue however is that sessions are not
  dropped.
• So they do not have to be set up again

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LISP-MN

• LISP-MN aims to make it possible for mobile
  devices to roam while keeping TCP sessions alive
  and to be simultaneously connected to two
  different networks. (Multihomed).
• LISP-MN is based on a LISP infrastructure

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LISP

• Lisp implements a Map-and-Encap scheme.
• Packets are encapsulated at the border router of
  the sender domain The Ingress Tunnel Router.
  (ITR)
• Packets are decapsulated at the border router of
  the receiver domain The Egress Tunnel Router
  (ETR)

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Encapsulation

• By this mechanism, core routing (routing between
  domains) is independent of the encapsulated
  endpoint identifiers.
• LISP adds an extra Internet layer below the
  existing one.

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LISP Stack
Application Layer
Identifier
Transport Layer
Identifier
Identifier
Internet Layer
Internet Layer
Locator
Data Link Layer
Physical Layer
LISP Stack
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LISP Transmission

1. The Host looks up the correspondent host in a DNS
   and gets an Endpoint Identifier
2. Host makes a packet with it source Endpoint
   Identifier and the Destination Endpoint
   Identifier
3. Packet is sent to the ITR which encapsulates it
   with the Routing Locator of the ITR as the
   source, and the Routing Locator of an ETR as the
   target. (This requires a mapping mechanism)
4. The packet is transmitted over the Internet to
   the ETR
5. The ETR decapsulates the packet and sends it to
   the destination Endpoint Identifier

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Typical LISP Scenario
RLOC ITR1 10.0.0.0/8
RLOC ETR1 12.0.0.0/8
EID 2.0.0.0/8
EID 1.0.0.0/8
Internet Core
ITR2 encapsulates The packet with source 1.0.0.1
and Destination 2.0.0.2 in a packet With source
11.0.0.1 And destination 12.0.0.2
The packet Arrives at ITR2
RLOC ITR2 11.0.0.0/8
RLOC ETR2 13.0.0.0/8
EID 1.0.0.1
EID 2.0.0.2
1.0.0.1 -gt 2.0.0.2
1.0.0.1 -gt 2.0.0.2
11.0.0.1 -gt 12.0.0.2
11.0.0.1 -gt 12.0.0.2
1.0.0.1 -gt 2.0.0.2
1.0.0.1 -gt 2.0.0.2
ETR! Forwards the packet To EID 2.0.0.2
Host EID 1.0.0.1 wants To send to Host EID 2.0.0.2
ITR2 does a DNS on 2.0.0.2 and gets13.0.0.2 and
12.0.0.2 The latter has priority
ETR1 receives the packet And decapsulates it.
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LISP-MN

• LISP-MN leverages the mapping infrastructure of
  LISP to support mobile devices
• This happens by turning the mobile device into a
  LISP ITR and ETR for itself
• The mobile device sends map requests
• All packets originating at the mobile device are
  LISP encapsulated

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Map Servers

• The mobile device can answer directly to incoming
  Map requests, or it can designate its map server
  as a proxy
• Map Servers have similar behaviour to Home Agents
  in Mobile IP
• Unlike mobile IP, the actual data never flows
  through these servers.
• They just answer to the mapping requests.
• Also, home agents never provide mapping
  information because that is left to the mobile
  node

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• Example EID 1.0.0.1 wants to send a packet to
  EID 1.0.0.2
• Mobile host 1.0.0.2 has lost its Wi Fi connection
  but still has GSM
• Mobile node updates the Mapping Server to
  indicate that it is accessible via 13.0.0.2, but
  not 12.0.0.2
• The packet arrives at ITR2 (Which has Routing
  Locator 11.0.0.1)
• ITR2 Looks up Routing Locators corresponding with
  EID1.0.0.2 and finds 13.0.0.2
• ITR2 encapsulates the packet and forwards as
  normal over the Internet core
• The mobile host receives the packet and
  decapsulates it.

WiFi 12.0.0.0/8
Mapping Server
RLOC Host
12.0.0.2 --------
13.0.0.2 1.0.0.2
RLOC ITR1 10.0.0.0/8
Domain EID 1.0.0.0/8
WiFi
Internet Core
3G
RLOC ITR2 11.0.0.0/8
3G 13.0.0.0/8
Source EID 1.0.0.1
Dest EID 1.0.0.2
1.0.0.1 -gt 1.0.0.2
11.0.0.1 -gt 13.0.0.2
11.0.0.1 -gt 13.0.0.2
11.0.0.1 -gt 13.0.0.2
1.0.0.1 -gt 1.0.0.2
1.0.0.1 -gt 1.0.0.2
1.0.0.1 -gt 1.0.0.2
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References

• CISCO Demo LISP_MN
• http//bit.ly/oYa2IE
• http//www.cisco.com/c/en/us/products/ios-nx-os-so
  ftware/locator-id-separation-protocol-lisp/index.h
  tml
• https//lispmob.org/
• http//lisp.cisco.com
• LISP Mobile Project (this is just a link of
  interest)
• http//www.lispmob.org/