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[RRG] thoughts on the design space 2: upper layer implications
- To: rrg <email@example.com>
- Subject: [RRG] thoughts on the design space 2: upper layer implications
- From: Jari Arkko <firstname.lastname@example.org>
- Date: Thu, 24 Jul 2008 15:21:32 +0300
- User-agent: Thunderbird 18.104.22.168 (X11/20080505)
This is a follow-up mail that attempts to list the different upper layer
implications the various design tree branches have.
The non-aggregatable designs such as ROFL have several issues:
- From what I understand, it is hard to implement routing policies. We
can't take away functionality that today's Internet system parts rely on.
- Addresses no longer provide any information about location, which is
something that some applications use today. Not clear how significant
this is, but I'm listing it here nevertheless.
The host-based identifier-locator split designs have the following issues:
- they break the 1 interface - 1 address assumption that many
applications have (draft-thaler 3.2.3)
- they cannot help with PI needs or avoid renumbering
- multihoming is not possible with existing peers, because they do not
support the extension. You can still communicate with existing peers,
Host-based IP layer designs have the following additional issues:
- Interference between what upper layers are doing with respect to
failure situations, for instance application fallback
- Interactions between transport layer actions and failure detection
schemes at IP layer
HIP, one of the host-based IP layer designs has the following further
- Addresses no longer provide any information about location
- If there is no mapping system from HITs to addresses, referrals become
Transport and higher layer solutions do not have additional issues.
The core-edge separation branch restores the notion that hosts have just
one address (by employing one prefix visible to the hosts). However, it
also introduces this issue:
- addresses provide locality information only within a domain
The encapsulation branch introduces these issues:
- reduced MTU, which can cause issues where PMTUD does not work (and it
does not work well today)
- difficulties in talking to the existing internet
All translation designs have issues with referrals.
Two-sided translation has the same issues as encapsulation, with the
possible exception of MTU differences.
One-sided translation has the issue that the addresses seen by one side
are not the same as those seen by the peer; NAT-like effects can be seen.
One-or-two sided translation has no additional issues when used to
communicate to an upgraded network. When used to communicate with a
legacy network, it has the same issues as one-sided translation.
The caching design has a number of issues:
- If packets are dropped while cache entries are being fetched, there
may be deterministic loss
- If packets are routed through a secondary path while cache entries are
being fetched, there may be deterministic delay
Both of these are issues (draft-thaler 3.1.6-3.1.7). Exactly how serious
issues is left for further study, however.
In addition, all designs with a mapping resolution system may have
incentive and reliability issues due to the fact that a third party is
needed. And, the non-caching design may have scalability issues.
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