Tunnels, IPv6, Mobile IP
– Tunneling and Virtual Networking – IPv6
– Mobile IP
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Tunneling and Virtual Networking
Traditional Connectivity
Private Network
• Corporates lease transmission lines/links
• Communication is restricted – Often for security reasons
• Isthisscalable?
Virtual Private Network (VPN)
• Idea is simple: replace dedicated medium with shared medium and provide a virtually private connection
How do we create a VPN?
• Wecannotjustconnectvarioussites
– Traffic between (A, B, C) and (K, L, M) should be private
• Tunneling
– Virtual point-to-point link between nodes that are separated by arbitrary number of networks
– Point-to-point link made through a public network – Links transport encapsulated datagrams
Example Tunnel
Outline Background
Structure Deployment
Who manages IP address blocks?
• Globally–IANA
– And by give regional Internet registries (RIRs) • ARIN, APNIC, LACNIC, AfriNIC, RIPE NIC
IP address exhaustion
IP address exhaustion
IPv4 exhaustion
IPv4 exhaustion
• On 31 January 2011, the last two unreserved IANA /8 address blocks were allocated
to APNIC according to RIR request procedures. This left five reserved but unallocated /8 blocks. In accord with ICANN policies, IANA proceeded to allocate one of those five /8s to each RIR, exhausting the IANA pool, at a ceremony and press conference on 3 February 2011.
IPv4 Address Allocation – 1998
Source: www.caida.org
Holes in v4 Address Space
• Each pixel represents a /24
• Routing tables were used to generate yellow portions of the table – routable addresses
– Incomplete view of the entire Internet
• Packet traces were used to generate black portions of the table – source/destination addresses
– Raises more questions than it answers
• Class A’s allocated to companies, etc. used for internal routing only (?)
• Class B & C allocation from lowest to highest
• Reserved address space
• Unallocated space
IPv6 Background
• IP has been patched (subnets, supernets) but there is still the fundamental 32 bit address limitation
• IETF started effort to specify new version of IP in 1991 – New version would require change of header
– Include all modifications in one new protocol
– Solicitation of suggestions from community
– Result was IPng which became IPv6 – First version completed in ’94
• Same architectural principles as v4 – only biggerJ CS 640 16
IPv6 planned support list
• 128-bit address space
– Thisiswhatit’sallabout…
• Real-time/QoS services
• Security and authentication
• Autoconfiguration
– Hosts autoconfig with IP address and domain name
– Idea is to try to make systems more plug-n-play
• Enhanced routing functionality eg. Mobile hosts
• Multicast
• Protocol extensions
• Smooth transition path from IPv4
– Can’t do it all at once!
Address Space and Notation
• Allocation is classless
– Prefixes specify different uses (unicast, multicast, anycast) • Anycast: send packets to nearest member of a group
– Address space division is based on leading bits
– Prefixes can be used to map v4 to v6 space and vice-versa
– Lots of flexibility with 128 bits!
• ~1500 address/sqft of the earths surface
• Standard representation is set of eight 16-bit values separated by colons
– Eg. 47CD:1234:3200:0000:0000:4325:B792:0428
– If there are large number of zeros, they can be omitted with series of colons
• Eg. 47CD:1234:3200::4325:B792:0428
– Address prefixes (slash notation) are the same as v4 • Eg. FEDC:BA98:7600::/40 describes a 40 bit prefix
Address Prefix Assignments
Unassigned
Reserved for NSAP (non-IP addresses used by ISO)
Reserved for IPX (non-IP addresses used by IPX)
Unassigned
Unassigned
Unassigned
Unicast Address Space
Unassigned
Unassigned
Unassigned
Unassigned
Unassigned
Unassigned
Unassigned
Unassigned
Unassigned
1111 1110 0
Unassigned
1111 1110 10
Link Local Use addresses
1111 1110 11
Site Local Use addresses
Multicast addresses
Unicast Assignment in v6
• Unicast address assignment is similar to CIDR
– Unicast addresses start with 001
– Host interfaces belong to subnets
– Addresses are composed of a subnet prefix and a host identifier
– Subnet prefix structure provides for aggregation into larger networks
• Some specific address blocks
– ::1/128 – Local host
– ::ffff:0:0/96 – IPv4 mapped addresses
• Address hierarchy
Recall IPv4 Packet Format Details
0 4 8 16 19
SourceAddr
DestinationAddr
Options (variable)
Pad (variable)
IPv6 Packet Format
0 4 8 16 24 31
Traffic Class
Flow Label
Payload Length
Next Header
SourceAddr (4 words)
DestinationAddr (4 words)
Next header (variable)
Packet Format Details
• Simpler format than v4
• Version = 6
• Traffic class same as v4 ToS (eg. low latency or high throughput)
• Treat all packets with the same Flow Label equally
– Support QoS and fair bandwidth allocation
• Payload length does not include header –limits packets to 64KB – There is a “jumbogram option”
• Hop limit is TTL field in v4
• Next header combines Options and Protocol fields in v4
– If there are no options then NextHeader is the protocol field
• Options are “extension header” that follow IP header
– Ordered list of tuples – 6 common types
• Quickly enable a router to tell if the options are meant for it
– Eg. routing, fragmentation, authentication encryption…
Key differences in header
• No checksum
– Bit level errors are checked for all over the place
• No length variability in header – Fixed format speeds processing
• No more fragmentation and reassembly in header
– Incorrectly sized packets are dropped and message is sent to sender to reduce packet size
– Hosts should do path MTU discovery
– But of course we have to be able to segment packets!
Fragmentation Extension
• Similar to v4 fragmentation
– Implemented as an extension header
• Placed between v6 header and data (if it is the only extension used)
– 13 bit offset
– Last-fragment mark (M)
– Larger fragment ID field than v4
• Fragmentation is done on end host
0 8 16 29 31
next header
Routing Extension
• Without this header, routing is essentially the same as v4
• With this header essentially same as the source routing option in v4
– Loose or strict
• Header length is in 64-bit words
• Up to 24 addresses can be included
– Packet will go to nearest of these in “anycast” configuration
• Segments left tracks current target
0 8 16 24 31
Next header
Hd. Ext. Len
Segmnts left
1 – 24 addresses
Transition from v4 to v6
• Flag day is not feasible
• Dual stack operation – v6 nodes run in both v4 and v6 modes and use version field to decide which stack to use
– Nodes can be assigned a v4 compatible v6 address
• Allows a host which supports v6 to talk v6 even if local routers only speak v4
• Signals the need for tunneling
• Add 96 0’s (zero-extending) to a 32-bit v4 address – eg. ::10.0.0.1
– Nodes can be assigned a v4 mapped v6 address
• Allows a host which supports both v6 and v4 to communicate with a v4 hosts
• Add 2 bytes of 1’s to v4 address then zero-extend the rest – eg. ::ffff:10.0.0.1
• Tunneling is used to deal with networks where v4 router(s) sit between two v6 routers
– Simply encapsulate v6 packets and all of their information in v4 packets until you hit the next v6 router
IPv6 Issues
• Address length: usable addresses vs. overhead
• Hop limit: is 65K necessary?
• Isthechecksumnecessary?
• How do servers handle both types of packets?
• Is security necessary in IP?
– How is it best implemented?
• DNS can be very important in the transition – how?
Intro to mobile IP Operation
Problems with mobility
We’re not quite done with IP
• You’re probably sick and tired of hearing about all things IP
– Forwarding, routing, multicast, etc…
• One last topic we must cover because it’s going to be important in the future – mobile networking
– Examples of mobile networking today?
– Examples of mobile networking tomorrow?
Mobility and Standard IP Routing
• IP assumes end hosts are in fixed physical locations – What happens if we move a host between networks?
• IP addresses enable IP routing algorithms to get packets to the correct network
– Each IP address has network part and host part
• This keeps host specific information out of routers
– DHCP is used to get packets to end hosts in networks • This still assumes a fixed end host
• What if a user wants to roam between networks?
– Mobile users don’t want to know that they are moving between networks
– Why can’t mobile users change IP when running an application?
• Mobile IP was developed as a means for transparently dealing with problems of mobile users
– Enables hosts to stay connected to the Internet regardless of their location
– Enables hosts to be tracked without needing to change their IP address
– Requires no changes to software of non-mobile hosts/routers
– Requires addition of some infrastructure
– Has no geographical limitations
– Requires no modifications to IP addresses or IP address format
• IETF standardization process is still underway
Home address and care-of address
TCP/IP Protocol Suite 34
Mobile IP has two addresses for a mobile host: one home address and
one care-of address.
The home address is permanent; the care-of address changes as the mobile host moves from one network to another.
TCP/IP Protocol Suite 35
Home agent and foreign agent
TCP/IP Protocol Suite 36
Figure 10.3 Remote host and mobile host configuration
TCP/IP Protocol Suite 37
Mobile IP Support Services
• Agent Discovery
– HA’s and FA’s broadcast their presence on each network to which they are attached
• Beacon messages via ICMP Router Discovery Protocol (IRDP) – MN’s listen for advertisement and then initiate registration
• Registration
– When MN is away, it registers its COA with its HA
• Typically through the FA with strongest signal
– Registration control messages are sent via UDP to well known port
• Encapsulation – just like standard IP only with COA
• Decapsulation – again, just like standard IP
Figure 10.7
Data transfer
TCP/IP Protocol Suite
Figure 10.8 Double crossing
TCP/IP Protocol Suite
Figure 10.9 Triangle routing
TCP/IP Protocol Suite
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