part 3: lecture 02 mobility · fixed network through wi-fi or femtocell in 2013!! offloading!...
TRANSCRIPT
Last time?!
802.11 alphabet! Wireless connections!
Access points!
Distributed Coordinated Function!
CSMA/CD versus CSMA/CA!
Hidden terminal!
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!
!
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
Public telephone network
Gateway MSC
G
3G (voice + data)!
radio network controller
MSC
SGSN
Public telephone network
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
Public telephone network
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.!
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.!
!
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.!
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.!
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?!!
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!
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!• 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
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.!
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.!
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!
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!• 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.!
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. !
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!
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!
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
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
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
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
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
Legend: EIDs -> Green Locators -> Red Physical link
PI EID-prefix 2.0.0.0/24
LISP-MN EID 3.0.0.3/32
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
Slides courtesy of !http://lispmob.org/!
Map reply!
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
Legend: EIDs -> Green Locators -> Red Physical link
PI EID-prefix 2.0.0.0/24
LISP-MN EID 3.0.0.3/32
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)
13.0.0.2, priority: 1, weight: 50 (D2)
Mapping Entry
Slides courtesy of !http://lispmob.org/!
LISP packet forwarding!
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
65.1.1.1PI EID-prefix
2.0.0.0/24
LISP-MN EID 3.0.0.3/32
66.2.2.2
Thispolicycontrolledbydestinationsite
EID-prefix: 3.0.0.3/32
Locator-set:
12.0.0.2, priority: 1, weight: 50 (D1)
13.0.0.2, priority: 1, weight: 50 (D2)
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
Legend: EIDs -> Green Locators -> Red Physical link
Slides courtesy of !http://lispmob.org/!
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!