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Computer Networks > IPv6 Migration > Flashcards

IPv6 Migration Flashcards

1
Q

IPv6 migration approaches

A
  • Dual Stack
  • Dual Layer
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2
Q

Dual stack migration approach

A

Dual Stack

  • Both capabilities in all entities supporting v6
  • v4 support can be graudally removed
  • Complete duplication of all protocol stack components
    • Routing protocols, tables, access lists
  • It doesn’t reduce the need for more v4 addresses
  • Application need to choose between v4 and v6.
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3
Q

Dual layer migration approach

A

Application are not responsible for choosing protocol to use: TCP/UDP selects most suited protocol (for example using information from DNS records (Type A, AAAA))

Less modifications in the applications

Less used than dual stack.

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4
Q

Travering IPv4 only network

A

Tunneling:

  • Encapsulating v6 packets in v4 packets emulating a directs link
  • End-point: hosts and routers
  • Protocols:
    • GRE
    • IPv6 in IPv4
  • Setup: manual and automatic
    • IPV4-compatible addresses
    • 6over4
    • 6to4
    • Tunnel broker
    • ISATAP
    • Teredo
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5
Q

Host centered vs Networks centered vs Carrier-Grade solution list

A

HC solutions: Dual stack hosts exchange IPv6 packets through an IPv4 network

  • ipv4 compatible addresses
  • 6over4
  • ISATAP

NC solutions: Dual stack and native v6 hosts exchange v6 packets through a v4 network.

  • Teredo
  • Tunnel Broker
  • 6to4

Scalable, CG solutions: Native IPv6 (ipv4) hosts exchange IPv6 (ipv4) packetrs through IPv4 (IPv6) network.

  • DS-lite
  • A+P
  • MAP-T and MAP-E
  • NAT64
  • 6PE (MPLS-based)
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6
Q

ipv6 migration: ipv4 compatible addresses

A

improperly called automatic tunneling

ipv4-compatible addresses (::/96) are used for v6 communication

process:

  1. app send ipv6 packets to ipv6 addresses
  2. static route forewards packets to ::/96 through pseudo-interface
  3. pseudo-interface encapsulates v6 packets in v4 packets and sends them out

If configured with dual stack router:

  1. pseudo-interface in sending host in is configured to terminate tunnels on router
  2. encapsulating v4 packets are sent to v4 address of dual stack router
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7
Q

6over4

A
  • Host cenetered solution in ipv6 transition
  • ipv4 networks emulates a virtual LAN
    • broadcast multiple access data link
    • ip multicasting used for the purpose
  • Neighbor and router discovery enabled
  • v4 address is used for automatic v6 interface ID generation of link local address
  • Not very used because of the lacking support for v4 multicast
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8
Q

6over4 neighbor discovery

A
  • ipv6 mutlicast addresses are mapped on ipv4 multicast addresses
    • 239.192.x.y where x.y are last 2 bytes of ipv6 address
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9
Q

ISATAP

A
  • Intra-site automatic tunnel addressing protocol
  • ipv4 netowrk as non-broadcast multiple access data link (NBMA)
    • No IP multicast suppport
  • Interface Id derived from lpv4 address
    • Prefixed by 0000:5efe
    • fe80::5efe:0101:0101
  • No neighbor discovery: not needed for data-link address discovery as ipv4 address is embedded in ipv6 address
  • PRL (Potential Router List) must be provided: router discovery is not possible
    • List usually obtained to DNS query to isatap.domain.com (usually domain is obtained through DHCP) or through configuration
    • Each router in the list is infrequently probed to check if they are working and to perform unicast-only configuration.
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10
Q

6to4

A
  • Network centered solution for ipv6 migration
  • Relay v4 address is embedded in ipv6 prefix by appending it to 2002::/16
    • 192.0.2.4 -> 2002:c000:0204::/48
  • Basic scenario: not meant for ipv4 host to ipv6 host communication
  • Mixed scenario (ipv4 global internet + ipv6 gobal internet): 6to4 relay must be default gatway (192.88.99.1) of 6to4 routers to handle cases of prefix not matching 6to4
    • Default gateway (6to4) realy: to be used whener I don’t know what to do with an ipv6 packet (prefix not matching 6to4 prefix)
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11
Q

Teredo

A
  • Solution to ipv6 transition with network centered approach
  • Architecture similar to 6to4
  • IPv6 packets are encapsulated in IP/UDP to be compatible with NAT, since NAT cannot use ports with IPV6 in IPv4.
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12
Q

Tunnel Broker

A
  • Solution to ipv6 transition with network centered approach
  • Solves the problem of 6to4: I cannot use a general ipv6 prefix
  • Tunnel broker server:
    • Indentifies tunnel servers (routers) and mediates tunnel setup (gives us the ipv4 addresses to contact)
  • IPv6 in IPv4 tunnels
  • Tunnel setup Protocol/Tunnel Information Control: protocol used to setup tunnels
  • 6to4 doens’t support any prefix, but is completely decentralized, doesn’t need central server, here we need it.
  • Who is in charge of the server (who pays for it) when it is shared between ISPs? big problem.
  • Pretty similar to ISATAP
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13
Q

Goal of Scalable, carrier grade solution to ipv6 transition

A

Goals:

  • need to support
    • ipv4 servers possibly communicating with ipv6 hosts
    • ipv4 clients
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14
Q

AFTR

A

Address family transition router:

  • allows ipv4 hosts to communcate wit ipv4 hosts over an ipv6 carrier infrastructure
    • residential hosts and current providers
  • features ipv6 tunnel concentrator and possibly a large-scale NAT
  • in use in DS-lite and A+P
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15
Q

DS-lite

A

Dual stack lite

  • Dual stack at the edge of the network
  • IPv6 only service provider backbone
  • Properties:
    • Reduces requirement for ipv4 addresses compared to dual-stack approach
      • dual-stack requires an ipv4 public address per host
    • Extended NAT enables customer assigned addressing
      • IPv6 address of CPE in NAT table
  • Limitation:
    • NAT is not under control of customer (same as with CarrierGradeNAT)
    • Problematic with servers (static mapping and port forwarding cannot be configured)
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16
Q

A+P

A
  • Address + Port
  • Carrier grade solution to ipv6 migration
  • NAT is under control of customer
  • Ranges of TCP/UDP ports are assigned to each customer
    • Only ports used by NAT on outside
  • Features
    • No problem with overlapping private address spaces at customers’
    • Ports acan be assigned automatically to CPE using the Port Control Protocol
      • CPE can negotiate more ports at any time
    • AFTR is just IPv4-in-IPv6 (proto-41) tunnel terminator
      • NAT44 is not needed
17
Q

MAP ipv6 migration

A
  • Mapping address and port
  • Multiple CPE use same public IPv4 address
  • set (not range) of ports assigned to cpe
  • Client ipv4 address and port set mapped to unique ipv6 address
    • prefix routed to cpe
  • ipv4 public server address mapped to unique ipv6 address
    • prefix routed to border relay
  • MAP-E (E stands for Encapsulation):
    • IPv4 packets are tunneled
  • MAP-T (translation): ipv4 translated to ipv6
18
Q

MAP port set

A

Port set:

  • Each CPE is assigned a unique PSID.
  • A > 0 is a bits; PSID is k bits; ; j is m bits.
  • a+ k + m = 16bits
  • The cpe uses ports with psid value, varying A and j.
19
Q

MAP CPE ipv6 address

A
  • EA(Embedded address) bits contain PSID and partial ipv4 address
    • uniquely identifis the cpe
20
Q

MAP border relay

A
  • BR address must be known to CPEs Multiple BRs might have same address
    • Anycasting
  • MAP-E: BR address terminates tunnel
  • MAP-T: prefix associated to BR used for translation of outside IPv4 addreses
    • BR prefix is advertised on the backbone
    • Might be advertised by multiple BRs
21
Q

NAT64 + DNS64

A

Principles:

  • an ipv6 prefix is dedicated to a mapped ipv4 address
  • dns64 maps A records (ipv4) into AAAA using NAT64 prefix, then serves A and AAAA records to the client
  • NAT64 router advertises NAT64 prefix into ipv6 network to attract traffic toward ipv4 hosts

Limitations:

  • Possible only when dns is involved
    • does not work if user specifies directly ipv4 address
  • no dnssec (authoritative dns signs records): since dns64 modifies records
22
Q

NAT64 + DNS64 deployment scenarios

A
23
Q

nat64 packet forwarding

A
  • Translates ipv6 adress and packet into ipv4
  • picks a free ipv4 address/port form its pool
  • build nat session entry
24
Q

DNS64 + NAT64 special case of no need for dns

A
25
Q

6PE

A
  • Only PE routers need to be changed
  • same mechanism as MPLS-based VPN
  • very scalable
  • Minimum configuration required
  • As more customers require ipv6 connectivity, provider might consider migrating to native support.
  • Internal routing
    • 6PE and P routers advertise their ipv4 prefixes with Labels bound to each PE
      • Topology based label binding.

In the image:

P-1, P-2: IPV4 only routers

PE-1,PE-2: Dual stack IPv4-IPv6 with MultiProtocol-BGP (MP-BGP)

26
Q

MPLS-Based solutions

A
  • Meant for interconnecting ipv6 islads through an ipv4 mpls backbone
  • most netowrk service providers deploy mpls anyway
  • IPv6 and MPLS:
  • Data plane is agnostic to ipv4/ipv6 (labels)
  • Control plane is not agnostic: destinations are identified through IP address.

Solutions:

  • Native IPv6 over MPLS
  • IPv6 over Circtuit Transport
  • 6PE
27
Q

Native IPv6 over MPLS

A
  • Control plane fully upgraded
  • IPv6 support in:
    • routing
    • label distribution protocol
    • management
  • Possibly Dual support
28
Q

IPv6 over Circuit transport

A
  • MPLS as layer 2 connectivity
    • LSP === L2 tunnel
  • PEs are ipv6 aware: static routes to ipv6 destinations and routing with remote PEs
  • No changes needed to P routers
  • It does not scale:
    • L2 tunnels routes are configured manually
    • possibly mesh topology of L2 tunnels
29
Q

Propagation and redistribution of routes, announcing ipv6 network with 6PE

A
  • Propagation of routes
    • 6pe exchange routing info through mp-bgp sessions over ipv4
    • 6pe ipv4-mapped address as BGP next hop
  • Announcing ipv6 networks
    • CE and 6PE connect through native ipv6 interfaces

routing information is exchanged

  • Redistribution of ipv6 routes
    • PEs propagate adv to ipv6 networks through IGP
    • May not be needed if CE-1 uses a default route
  • Label distribution
    • For ipv4 dest. among P and 6PE routers
      • LDP or RSVP
    • For ipv6 routers: directly between 6PE, using MP-iBGPv4
30
Q

6PE packet forwarding

A
  • CE routers send IPv6 packets to 6PE routers
  • 6PE has label mapping for destination
    • was distributed by iBGP
    • next hop: 6PE identified the BGP next hop
      • ipv4-mapped ipv6 address
  • Next hop is reachable through ipv4 (IGP said that)
    *

Computer Networks (12 decks)

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