12. Routing Futures

Question 1

Sire requirements - Four broad classes of site

Answer 1

• SOHO Networks - unmanaged, usually single subnet, likely to grow in future
• Enterprises - managed, multiple (sub)networks, internal routing
• Distributed enterprises - multiple sites, likely to have dedicated inter-site interconnects
• Mobile Netowrks (emerging) - will change their point of attachment over time

Question 2

Site requirements

Answer 2

Provider Independence
Multihoming
Traffic Engineering

Question 3

Provider independence

Answer 3

Should be easy to for a site to change provider

• avoid dependence on any given ISP
• by default, sites get PRovider Aggregatable (PA) address space from theis ISP - so it depends on its ISPs overall address space
• will want to avoid network renumbering when changing ISP

Question 4

Provider independence facilitated in these ways

Answer 4

• Using Provider Independent (PI) address space - where available
• Using NAT at the site border - map from internal prefix to external prefix/addresses; limits connectivity into the site though
• Using historically assigned IP address blocks

Question 5

RIPE is the RIR for our region

Answer 5

RIPE - Réseaux IP Européens

RIR - Regional Internet Registry

Question 6

Multihoming

Answer 6

Using multiple providers
-multiple points of attachment and/or ISPs
Various reasons to multi-home
- resilience
- load balancing
Leads to more prefixes being advertised
- may be achieved using a new PI prefix
- may be done by advertising a more specific prefix from one ISP through another ISP
The pain is pushed to the network core
- increased de-aggregation (more prefixes in tables)
- more ASNs (Autonomous System Number)