Hi, Ron,
On 7/5/2016 7:54 AM, Ron Bonica wrote:
> Inline......
>
>> -----Original Message-----
>> From: Joe Touch [mailto:[email protected]]
>> Sent: Friday, July 1, 2016 1:25 PM
>> To: Ronald Bonica <[email protected]>; [email protected]
>> Subject: Re: [Int-area] FW: New Version Notification for
>> draft-bonica-intarea-
>> eping-00.txt
>>
>> Hi Ron,
>>
>> On 7/1/2016 9:47 AM, Ronald Bonica wrote:
>>> Hi Joe,
>>>
>>> Good to hear from you! Responses inline.......
>> Same here on both counts...
>>> Ron
>>>
>>>> First, IP addresses can be assigned to interfaces or hosts.
>>>> Interfaces don't have to have IP addresses, esp. point-to-point
>>>> interfaces or those used "anonymously" (e.g., for broadcast
>> send/receive).
>>> [RB ]
>>> Absolutely. In the draft, we talk about "unnumbered interfaces". These are
>> interfaces to which an IP address has not been assigned.
>> I'm talking about numbers assigned to the host, not the interface. What kind
>> of response are you expecting there?
>> ...
> [RB ]
> [RB ]
> Since the host has an address, the destination and probed addresses would be
> the same. In this case, eping behaves exactly the same as traditional ping.
I'm referring to the text, not the behavior. I agree the behavior would
be as expected.
The text should address the case above, however - it should not assume
that all IP addresses are always associated with interfaces.
...
>>>
>>>> Additionally, I think this might have an existing equivalent when the
>>>> probed interface has an address, e.g., it really seems like it ought
>>>> to be equivalent to an IP with LSR whose destination IP is the
>>>> "destination" and whose probe IP is the LSR "next hop". In a sense,
>>>> it seems like you're just extending ping with LSR that allows for
>>>> using ifName, ifIndex, or non-IP addresses rather than just IP addresses.
>> It might be useful to describe that way, FWIW.
>>> [RB ]
>>> I'm not sure that I follow this paragraph.
>> Let's say a device has two interfaces with addresses A and B.
>>
>> I might not be able to ping address B because of routing between me and
>> that device.
>>
>> However, I might be able to ping B via a LSR through A.
>>
>> Isn't that largely how this IDs approach works when you're using a
>> single AF with numbered interfaces?
>>
> [RB ]
> Ah! Now I understand what you are saying.
>
> Let's do a thought experiment. Assume that a router has three interface, A,
> B, and C. Assume also that all three interfaces are up. A network operator
> needs to know the status of Interface B, so he executes traditional PING. The
> ICMP Echo Request message enters the router through Interface C and the ICMP
> Echo Response leaves through Interfaces C. The operator learns that Interface
> B is up, but he does not know whether his ping exercised interface B. (In
> this case, it didn't.)
>
> The next day, the operator removes the address from interface B, so he can't
> ping it any longer. But he needs to know Interface B's status. So, he sends
> executes eping, with Interface A as the destination interface and Interface B
> as the probed interface. The ICMP Extended Echo Request message enters the
> router through Interface C and the ICMP Extended Echo Response leaves through
> Interfaces C. The operator learns that Interface B is up, but he does not
> know whether his ping exercised interface B. (In this case, it didn't.)
The case you're giving is the one in which an operator can find out
about an interface without an IP address - which I agree this method
enables.
I'm speaking of a different case:
- send a ping to interface B
let's say that ping fails because you don't have a route to B
that would fail for both ping and eping
- send a ping to interface C
let's say that works because you do have a route to C
that would work for both ping and eping
- send a ping LSR to B via C
that ping seems like it would work now, i.e., LSR ping would reach B
and get a response through C even though B isn't directly reachable
that would work for both ping and eping
The unique aspect of eping is being able to ping (or get status) about
interfaces without names. Both LSR ping and eping are equally capable of
getting status about an *address* that is not otherwise reachable (e.g.,
because of routing issues).
Joe
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