inter-domain link recovery
rdobbins at cisco.com
Wed Aug 15 05:08:15 UTC 2007
On Aug 14, 2007, at 9:06 PM, Chengchen Hu wrote:
> 1. Why BGP-like protocol failed to recover the path sometimes? Is
> it mainly because the policy setting by the ISP and network operators?
There are an infinitude of possible answers to these questions which
have nothing to do with BGP, per se; those answers are very
subjective in nature. Can you provide some specific examples
(citing, say, publicly-available historical BGP tables available from
route-views, RIPE, et. al.) of an instance in which you believe that
the BGP protocol itself is the culprit, along with the supporting
data which indicate that the prefixes in question should've remained
globally (for some value of 'globally') reachable?
Or are these questions more to do with the general provisioning of
interconnection relationships, and not specific to the routing
protocol(s) in question?
Physical connectivity to a specific point in a geographical region
does not equate to logical connectivity to all the various networks
in that larger region; SP networks (and customer networks, for that
matter) are interconnected and exchange routing information (and, by
implication, traffic) based upon various economic/contractual,
technical/operational, and policy considerations which vary greatly
from one instance to the next. So, the assertion that there were
multiple unaffected physical data links to/from Taiwan in the cited
instance - leaving aside for the moment whether this was actually the
case, or whether sufficient capacity existed in those links to
service traffic to/from the prefixes in question - in and of itself
has no bearing on whether or not the appropriate physical and logical
connectivity was in place in the form of peering or transit
relationships to allow continued global reachability of the prefixes
> 2. What is the actions a network operator will take when such
> failures occures? Is it the case like that, 1)to find (a)
> alternative path(s); 2)negotiate with other ISP if need; 3)modify
> the policy and reroute the traffic. Which actions may be time
All of the above, and all of the above. Again, it's very
> 3. There may be more than one alternative paths and what is the
> criterion for the network operator to finally select one or some of
Proximate physical connectivity; capacity; economic/contractual,
technical/operational, and policy considerations.
> 4. what infomation is required for a network operator to find the
> new route?
By 'find the new route', do you mean a new physical and logical
interconnection to another SP?
The following references should help shed some light on the general
Roland Dobbins <rdobbins at cisco.com> // 408.527.6376 voice
Culture eats strategy for breakfast.
-- Ford Motor Company
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