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COMP3010 - Advanced Networks > 9. IPv6 Transition I > Flashcards

9. IPv6 Transition I Flashcards

1
Q

Reasons for deploying IPv6

A
  1. Exhaustion of IPv4 address space
  2. Enabling End-to-End global addressing
  3. Securing IPv6 in your own ‘IPv4 only’ network
  4. Enabling innovation/research/teaching
  5. Deploy in a limited scenario to gain experience
  6. Simplify early adopter IPv6-only access networks’ ability to reach you
  7. New applications; sensors, logistics, transport
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2
Q

Reasons against deploying IPv6

A
  1. I have enough global IPv4 addresses
  2. I like NAT
  3. Adding IPv6 adds cost/complexity
  4. No time/money/not a priority
  5. Don’t need to talk to IPv6 only devices yet
  6. Lack of support in certain apps/systems
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3
Q

NAT

A

Network Address Translation

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4
Q

IPv6 Deployment Approaches

A

Enable IPv6 capability upon the existing IPv4 infrastructure:
- run both protocols on same devices - known as dual stack
- should enable the network infrastructure before hosts/apps
- ensure connectivity, security & monitoring all are robust 1st
Initial capability may be in islands:
- need ways to connect IPv6 enables networks across intervening IPv4 only networks
- implies some form of tunnelling or encapsulation of traffic

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5
Q

Deploy IPv4/IPv6 dual-stack

A

Existing network runs IPv4
- introduce IPv6 to same network infrastructure
- known as dual-stack operation
- hosts and routers are able to communicate using either protocol and can thus also talk to IPv4-only or IPv6-only devices
Choice of protocol is application-specific
- DNS returns IPv4 and IPv6 addresses for a given hostname
- MS IE prefers IPv6 but can fall back to IPv4 (Chrome/Firefox try both, pick up whichever first connects)
- need to be confident IPv6 connectivity is good else the application may perform worse than IPv4-only network

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6
Q

Connecting IPv6 islands

A

May wish to deploy IPv6 at a site (eg campus) and then use IPv6 to communicate with remote IPv6 sites
- intervening networks may be IPv4 only, implies a tunnelling method
What type of tunnels might we need
- router to router (site to site)
- host to router (host to site)
Tunnels could be set up manually or automatically

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7
Q

Tunnelling

A

IPv6 packets encapsulated in IPv4 packets
- IPv6 packet is payload of IPv4 packet
Usually between routers to connect IPv6 islands
- edge router talks IPv6 natively to internal systems
- encapsulates IPv6 in IPv4 towards remote tunnel endpoint

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8
Q

Packet delivery over the tunnel

A
  1. IPv6 node A sends packet towars IPv6 node B
    - routed internally to edge router A
  2. Edge router A sees destination network B is reachable over tunnel interface
    - encapsulates IPv6 packet in IPv4 packet/s
    - sends resulting IPv4 packet/s to edge router B
    - delivered over existing IPv4 internet infrastructure
  3. Edge router B decapsulates IPv6 packet from payload of received IPv4 packet
    - packet routed internally in network B towards node B
    - Node B receives the IPv6 packet
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9
Q

Manually configure tunnels

A

Easy to set up and configure
- tedious if crating lots, or changing daily
Good management potential
- may be used by an ISP to connect sites using IPv6 over their current IPv4 only infr
- ISP configures all tunnels, so in control of deployment
- this is the current approach used by JANET to connect UK academic sites over IPv6 where native IPv6 connectivity is not available in the regional networks
- sites use a manually configured tunnel to a JANET access router

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10
Q

Connecting single hosts

A

An individual user - tunnel from their device to access IPv6

  • eg user with a dual-stack device in a home ADSL network
  • desirable to allow end user to register and subsequently authenticate to request a tunnel
  • the IPv6 Tunnel Broker offers such a system, usually for host-to-router connectivity
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11
Q

Tunnel Broker

A

service which provides a network tunnel.
IPv6 tunnel brokers typically provide IPv6 tunnels to sites or end users over IPv4. In general, IPv6 tunnel brokers offer so called ‘protocol 41’ or proto-41 tunnels. These are tunnels where IPv6 is tunneled directly inside IPv4 packets by having the protocol field set to ‘41’ (IPv6) in the IPv4 packet.

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12
Q

Tunnel Broker MO

A

User/client registers with the broker system
A tunnel is requested from the user’s IPv4 address
The broker sets up its end of the requested tunnel on its tunnel server
The broker communicates the tunnel settings to the user for the client side configuration
User’s system executes script, establishing the tunnel

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13
Q

Broker issues

A

Key advantage is its manageability
ISP running the broker can track usage levels
A few downsides
- if broker topologically remote, round trip times for data might suffer
- traffic within the ISP is concentrated through the broker
- if using a remote tunnel broker, your own ISP may not perceive demand for IPv6
- Need additional client capability to handle IPv4 NAT traversal or a SOHO having a dynamic IPv4 address (HE broker uses a heartbeat protocol)

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14
Q

Automatic tunneling

A

Goal - avoid requiring support staff effort to setup and maintain tunnels
- set up required tunnels on demand
- keep deployment and usage simple for the end user
Most common automatic method is 6to4
( used router to router
widely available,
proven problematic as IPv6 has matured)

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15
Q

6to4

A

used to automatically connect two IPv6 islands across an intermediate IPv4-only network

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16
Q

6to4 dedicated IPv6 prefix

A
  • the 2002::/ prefix is used for 6to4 use
  • next 32 bits of the 6to4 prefix are the 32bits of the IPv4 address of the 6to4 router
    When a 6to4 router sees an IPv6 packet with destination prefix 2002::/16, it knows to tunnel the packet in IPv4 towards the IPv4 address indicated in the next 32 bits
17
Q

6to4 features

A

Good

  • simple to deploy and use
  • fully automatic; no admin effort per tunnel
  • tunneled packets automatically route efficiently to the destination network (following the best IPv4 path over the IPv4 internet)
18
Q

Missing feature of 6to4

A

How does a node on a 6to4 site communicate with an IPv6 node on a regular ‘real’ IPv6 site
(site without 6to4 support)?
Use 6to4 relay
- dual stack router with a 6to4 interface and a real ‘native’ IPv6 interface (it can route traffic between the two domains)

19
Q

6to4 relay, handling the 6to4 traffic

A
  1. IPv6 packets sent from a 6to4 site to a destination address outside 2002::/16 are tunnelled using 6to4 to the relay, are decapsulated and forwarded on the relay’s ‘real’/native IPv6 interface to the destination site
  2. IPv6 packets sent from a ‘real’/native IPv6 site towars an address using the 2002::/16 prefix (a 6to4 site) are routed to the 6to4 relay and then tunnelled using 6to4 to the destination 6to4 site
20
Q

Routing to/from the relay

A

The 6to4 relay needs to be ‘discovered’ by IPv4 routers in the 6to4 world and IPv6 routers in the ‘rea’/native IPv6 Internet
- all 6to4 routers can be configured to tunnel to a well known anycast address for the relay for which 192.88.99.1 has been assigned.
The 6to4 relay advertises a host route for this address, allowing 6to4 routers to use the nearest 6to4 relay
- the 6to4 relay advertises 2002::/16 to the ‘real’ IPv6 Internet using BGP or similar routing protocol, BGP then determines the closest relay for a ‘real’ IPv6 site to use to reach a 6to4 site

21
Q

6to4 issues

A

Some operational concerns
1. possible relay abuse
- relay could be used for for a DoS attack if tunnelled IPv6 traffic addresses are spoofed
2. asymetric model and reliability issues
- 6to4 site might use a different 6to4 relay to the real IPv6 site - debugging fun :)
- one of the sites may not see a 6to4 relay at all if ISPs choose to only deploy relays for their own customers
But for 6to4 to 6to4 site operation its good

22
Q

6rd

A

a new variant of 6to4
The 6rd protocol removes many of the problems associated with 6to4
- works like 6to4 but the ISP running 6rd uses its own regular IPv6 network prefix not the 2002::/16 prefix
(Tunnelling only happens within the ISP itself)
- this change ensures traffic from regular, native IPv6 sites is routed to the ISP’s own network (no such guarantee with 6to4)

COMP3010 - Advanced Networks (19 decks)

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