part 3: lecture 02 mobility · ﬁxed network through wi-fi or femtocell in 2013!! ofﬂoading!...

Part 3: Lecture 02!Mobility!

Last time?!

802.11 alphabet! Wireless connections!

Access points!

Distributed Coordinated Function!

CSMA/CD versus CSMA/CA!

Hidden terminal!

Mobile traffic!

Some facts (I)!1.  Global mobile data traffic grew 63 percent in 2016.!

–  From 4.4 exabytes/month in Dec 2015 to 7.2 exabytes/month in Dec. 2016!

!2.  Mobile traffic has grown 18 –fold in the past 5 years!

–  400 petabytes/month in 2011 exabyte!!

3.  Over half a billion (429million) mobile devices and connections were added in 2016!–  The total number of mobile devices is now 8 billions!!

Some facts (II)!4.  In 2016 26% of the mobile connections are 4G. They generate

69% of the mobile traffic.!

5.  Mobile video traffic exceeds 60 percent of the total traffic.!–  It is expected that in 2018 video will represent 2/3 of the mobile

traffic.!!

6.  60 percent of total mobile data traffic was offloaded onto the fixed network through Wi-Fi or femtocell in 2013!

!

Offloading!

Cellular networks!

Cellular networks architectures!

Mobile Switching

Center

Public telephone network

Mobile Switching

Center

•  connects cells to wired tel. net.!•  manages call setup!

MSC •  covers geographical region!•  base station (BS) analogous

to 802.11 AP!•  mobile users attach to

network through BS!•  air-interface: physical and

link layer protocol between mobile and BS!

cell

wired network

2G (voice)!

BSC BTS

Base transceiver station (BTS)

Base station controller (BSC)

Mobile Switching Center (MSC)

Mobile subscribers

Base station system (BSS) MSC


Gateway MSC

G

3G (voice + data)!

radio network controller

MSC

SGSN


Gateway MSC

G

Serving GPRS Support Node (SGSN)

Gateway GPRS Support Node (GGSN)

Public Internet

GGSN

G Key insight: new cellular data!network operates in parallel !(except at edge) with existing !cellular voice network!v  voice network unchanged in core!v  data network operates in parallel!

radio network controller

MSC

SGSN


Gateway MSC

G

Public Internet

GGSN

G

radio access network Universal Terrestrial Radio Access Network (UTRAN)

core network General Packet Radio Service

(GPRS) Core Network

public Internet

radio interface (WCDMA, HSPA)

3G architecture!

Long Term Evolution!Initiated in 2004 by NTT DoCoMo, focus on enhancing the Universal Terrestrial Radio Access (UTRA) and optimizing 3GPP’s radio access architecture!•  LTE is not 4G – sometimes called 3.9G!!•  Simplified network architecture: flat IP-based network replacing

the GPRS core, optimized for the IP-Multimedia Subsystem (IMS), no more circuit switching!

•  Much higher data throughput supported by multiple antennas!•  Much higher flexibility in terms of spectrum, bandwidth, data

rates!•  Much lower RTT – good for interactive traffic and gaming!!

LTE advanced!•  Worldwide functionality & roaming!•  Interworking with other radio access systems!•  Enhanced peak data rates to support advanced services and

applications (100 Mbit/s for high and 1 Gbit/s for low mobility)!•  Relay Nodes to increase coverage!•  100 MHz bandwidth (5x LTE with 20 MHz)!

All IP core !•  The EPC - Evolved Packet Core!

•  Allows for subscriber tracking, mobility management, and session management in the network.!

EPC architecture!

SGW/PDNGW!The gateways (Serving GW and PDN GW) deal with the user plane. !!They transport the IP data traffic between the User Equipment (UE) and the external networks.!!SGW: point of interconnect between the radio side and the EPC!PDNGW: point of interconnect between the EPC and the external IP networks!

Mobile users versus fixed users!

•  Number of mobile Internet users/hosts is surpassing the number of fixed internet users/hosts.!

!

Mobility!

Handovers!1.  Mobile hosts are becoming multiple radio devices (wifi and

cellular net)!

2.  Handover:!–  Vertical handover: from Wi-Fi to cellular.!–  Horizontal handover: between the same technology !!

3.  IP is the convergence technology with packet switching capabilities on all devices.!

Without moving….!

… and now?!

The IP address ‘problem’!•  The problem is that an IP address is both:!

The node identifier, i.e. who you are;!

The node locator, i.e. where you are.!

Sessions and mobility!•  How do you ensure that communication is uninterrupted when

one of the endpoints moves? !!In other words:!•  How do you achieve session persistence?!

Session = shared state for a communication that is not specific to the network path. Sessions can one-to-one, one-to-many, many-to-many.!

How to solve this?!•  Accept that sessions will not persist: nomadic or roaming

access!

Roaming on WiFi!

Nomadicity/roaming!•  Sessions can break....!•  ... but you can access the Internet regardless of location and

time.!!

IP address will change when the attachment point changes

Hotspots!•  Hundreds of APs that have an extensive coverage.!

–  Campuses!–  Cities!

•  Not the same range as cellular nets.!

•  How can hotspots operators provide access beyond their geographical area? !

•  How do you allow roaming over different WiFi hotspots or nets?!!

3 WiFi roaming models!1.  National Operator!

2.  Broker!

3.  Federation !

802.11u!When you see a WiFi network, how do you know which one has a roaming agreement with the home operator?!

802.11u = a standard to provide interworking with external networks.!!•  Mobile Wi-Fi radio wakes up periodically and scans!•  Mobile actively scans for hotspot and receives:!

•  Internetworking element, identifying AP as 802.11u capable!•  Roaming consortium element advertising hotspot owner OUI + top 2!

roaming partner’s OUIs!•  If mobile recognizes OUI, then attempts association using security credentials

corresponding to that OUI!

Hotspot 2.0/ Wi-Fi Passpoint!•  Automatically join a Wifi network (without to login)!

eduroam!

Radius hierarchy!

Network Layer Mobility!

Network layer mobility problem!

Transport layer mobility problem!

How to solve this?!

•  Tunneling, i.e. host appears as being on the same ‘old’ network!

•  Accept that sessions will not persist: nomadic or roaming access!

Layer 3 mobility!•  Seamless mobility: persistence of the TCP session when end

node changes attachment point in the network.!

•  Achieved by using two separate IP addresses for identification and routing:!–  Mobile IPv4!–  Mobile IPv6 !

Mobile IPv4!

Mobile IPv4!•  The static node is not aware the other side is moving. This

means Mobile IPv4 creates an overlay network on top of the existing Internet model.!

Learn more: IP Mobility Support for IPv4, revised RFC 5944 – Nov. 2010

Network domains!•  Home network!•  Virtual network!•  Foreign network !

–  Visited network!

Network elements !

•  Mobile node!•  Foreign agent!•  Home agent!•  Corresponding node!

Addressing terms!

•  HoA - home address!•  CoA - care-of address, !

–  foreign agent CoA !–  colocated care-of address

(CCoA).!

Operation!•  The home agent needs to build a internal database to:!

–  Track a mobile node!–  Determine how to route traffic to it. !!

•  Three functionalities:!–  Agent discovery!–  Registration and AAA!–  Tunnels, bindings and datagram forwarding!

Agent discovery!•  To determine the network to which it is connected the mobile

node can:!–  listen for Agent Advertisements messages!

•  Multicast messages based on an extension of the ICMP router advertisements !

–  elicit an Agent Advertisement message by sending an Agent Solicitation message!

Flags meaning!Flag Meaning

R! The mobile nodes must complete registration procedures to make use of this foreign agent.!

B! The agent is busy and will not accept registrations from additional mobile nodes.!

H! This agent offers service as a home agent on the link on which this Agent Advertisement message was sent.!

F! This agent offers service as a foreign agent on the link on which this Agent Advertisement message was sent.!

M! This agent supports receiving tunneled datagrams (from the home agent) that use minimal encapsulation as defined in RFC 2004.!

G! This agent supports receiving tunneled datagrams (from the home agent) that use GRE encapsulation as defined in RFC 2784.!

r! Reserved (must be zero).!

T! This agent supports reverse tunneling as defined in RFC 3024.!

U! Mobility agent supports UDP Tunneling.!!

X! Mobility agent supports Registration Revocation!

I! Foreign agent supports Regional Registration !

Registration - RRQ!•  RRQ - registration request - are messages from the mobile node and

destined for mobility agents.!•  They allow to:!

–  request service from a foreign agent (optional)!–  inform the home agent of its current CoA (registration)!–  renew a registration about to expire (reregistration)!–  deregister!

Registration - RRP!•  The mobile agent replies with a RRP - registration reply-

message!•  RRQs and RRPs use UDP. Reliability is guaranteed by Mobile

IPv4 in the form of retransmission capabilities, validity checksums and session identifications.!

Registration process!

Packets delivery!When the CoA is the Foreign Agent:!

Packets delivery!When the mobile node uses a CCoA!

AAA !•  Mobile IPv4 messages rely on shared authentication values, known as message

authentication codes, for authenticating messages sent from the mobile node to a mobility agent, and between mobility agents.!

Mobile IPv4 and RADIUS!

Triangular routing!

Reverse tunneling!In case bidirectionality needs to be maintained:!

Pause!

What will happen if mobile node and corresponding node are local?!

Standard ARP functionality!

The correspondent node is local!

Mobility challenge!

ARP rules in Mobile IP!•  Proxy ARP!

–  An ARP reply sent by one node on behalf of another node!–  ARP reply includes proxy’s link-layer address!–  Future transmissions will be sent to the proxy!–  Home agent can proxy ARP for mobile node!

•  Gratuitous ARP!–  ARP request or reply sent in order to update ARP caches at other

nodes!–  Nodes are required to update their caches!–  Home agent does gratuitous ARP to update ARP caches on local

network after change in registration or deregistration!–  Mobile host does gratuitous ARP when it returns home!

Home agent Proxy ARP!

Home agent Gratuitous ARP!

What are the problems with MobileIPv4?!!

Some… !•  Triangular routing.!

–  delays the delivery of the datagrams and places an unnecessary burden on networks and routers!

•  Firewalls!–  blocking incoming from the Internet that appear to emanate from

internal computers !•  Border routers!

–  discarding packets coming from within the enterprise if the packets do not contain a source IP address configured for one of the enterprise's internal networks !

Mobile IPv6!

Mobile IPv6!•  There are no foreign agents. For the rest the functionalities are

the same as in Mobile IPv4.!

•  Majority of traffic is sent to the mobile node using the IPv6 routing header structure. Including a new Mobility Header!

•  Does not rely on ARP, but uses IPv6 neighbour discovery.!

!

Two modes of operation!Bidirectional tunnelingUsed when the corresponding node does not support MobileIPv6.!!Requires IPv6 neighbour discovery in the home agent.!

Two modes of operation!Route optimization

Headers!

Destination Option Header! Type 2 routing header!

Used by the mobile node to notify the corresponding node of its home address.!The corresponding node replaces the IPv6 source address with the home address recovered with this option.!

Used by corresponding node to include the mobile node home address.!!The mobile node replaces the IPv6 destination address with the home address recovered with this option.!

Route optimization pros!

•  Allows the shortest communications path to be used. !

•  Eliminates congestion at the mobile node's home agent and home link. !

•  The impact of any possible failure of the home agent or networks on the path to or from it is reduced. !

IPv6 binding procedure!

IPv6 Return routability procedure!

How to solve this?!

•  Use domain names of hosts instead of IP address AND update the DNS server when on new network.!

•  Tunneling, i.e. host appears as being on the same ‘old’ network!

•  More radical approaches:!–  Separate locators and identifiers by redesigning the TCP/IP stack!

•  Accept that sessions will not persist: nomadic or roaming access!

Locator-Identifier separator!

Approaches!•  Introduce an extra layer in the OSI stack!•  Split the existing IPv6 addresses into a part with topological

meaning and a part that uses to identify the host.!

Do this:!•  On the host!•  At the border between a site and the core network!

Test !

LISP (I)!•  Locator-Identifier Separation Protocol – LISP - implements a

Map-and-Encap scheme to decouple location and identity.!

•  RLOCs – routing locators: how a node is attached to the network!

•  EID – Endpoint identifiers – who the node is!

LISP:!•  requires no hardware / software changes to hosts!•  is incrementally deployable in the network infrastructure!•  is a simple, open standard protocol (IETF)!

!

Two namespaces and mappings!

•  Egress Tunnel Router (ETR): !the tunnel endpoint;!!•  Ingress Tunnel Router (ITR): !the tunnel start point; !!•  xTR: !an ETR/ITR!

PrefixNext-hopw.x.y.1 e.f.g.h x.y.w.2 e.f.g.h z.q.r.5 e.f.g.h z.q.r.5 e.f.g.h

Non-LISP

RLOCSpace

EID-to-RLOCmapping

xTR

EIDSpacexTR

EID RLOCa.a.a.0/24 w.x.y.1 b.b.b.0/24 x.y.w.2 c.c.c.0/24 z.q.r.5 d.d.0.0/16 z.q.r.5

MS/MR

PxTR

xTR



EIDSpace

Map registration!

S1

S2

TR

TR

S

Provider A 10.0.0.0/8

Provider B 11.0.0.0/8

Provider X 12.0.0.0/8

Provider Y 13.0.0.0/8

LISP Site

Mapping System MR MS

10.0.0.1

11.0.0.1 13.0.0.2

12.0.0.2

LISP Site

65.1.1.1

12.0.0.2-> 66.2.2.2 LISP Map-Register

(udp 4342) SHA-1

3.0.0.3/32 12.0.0.2, 13.0.0.2

PI EID-prefix 2.0.0.0/24

LISP-MN EID 3.0.0.3/32

66.2.2.2

Slides courtesy of !http://lispmob.org/!

Map request!

S1

S2

TR

TR

S





LISP Site


10.0.0.1

11.0.0.1 13.0.0.2

12.0.0.2

LISP Site

65.1.1.1

Legend: EIDs -> Green Locators -> Red Physical link



DNSentry:D.abc.comA3.0.0.3

How do I get to 3.0.0.3?

11.0.0.1 -> 3.0.0.3 Map-Request

(udp 4342) nonce

11.0.0.1 -> 65.1.1.1 LISP ECM (udp 4342)

[1]

[2]

[3] [4]

11.0.0.1 -> 3.0.0.3 Map-Request

(udp 4342) nonce

66.2.2.2

2.0.0.2 -> 3.0.0.3


Map reply!

S1

S2

TR

TR

S





LISP Site


10.0.0.1

11.0.0.1 13.0.0.2

12.0.0.2

LISP Site

65.1.1.1




66.2.2.2

12.0.0.2 ->11.0.0.1 Map-Reply (udp 4342)

nonce 3.0.0.3/32

12.0.0.2 [1, 50] 13.0.0.2 [1, 50]

[6] EID-prefix: 3.0.0.3/32

Locator-set:

12.0.0.2, priority: 1, weight: 50 (D1)


Mapping Entry


LISP packet forwarding!

S1

S2

TR

TR

S





LISP Site


10.0.0.1

11.0.0.1 13.0.0.2

12.0.0.2

LISP Site

65.1.1.1PI EID-prefix

2.0.0.0/24


66.2.2.2

Thispolicycontrolledbydestinationsite

EID-prefix: 3.0.0.3/32

Locator-set:



Mapping Entry

3 2.0.0.2 -> 3.0.0.3

2

2.0.0.2 -> 3.0.0.3 11.0.0.1 -> 12.0.0.2

4

2.0.0.2 -> 3.0.0.3 11.0.0.1 -> 12.0.0.2

7



Literature!

Many figures used in these slides comes from the “building mobile internet” book. See: http://eetimes.com/design/embedded/4234424/Mobile-Internet-basics--Transport-layer-mobility-challenges

Chapter 6 - Wireless and mobile networks!

Part II – Mobility approaches!

The end…. Or nearly.!

IoT – Internet of Things!

Preparation for the exam!The “Course material” page on the Wiki is the reference for the exam.!!Exam is open book.!2.5 hours.!!See you Tuesday 30th.!10.30-13.00!!Example exam from last year (2016) to be found online.!!

part 3: lecture 02 mobility · ﬁxed network through wi-fi or femtocell in 2013!! ofﬂoading!...

Documents