Re: [Ila] [5gangip] ILA forwaring [Was Re: Problem Statement]

"FIGURELLE, TERRY F" <> Tue, 01 May 2018 19:02 UTC

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To: Tom Herbert <>, Dino Farinacci <>
CC: Tom Herbert <>, "" <>, Behcet Sarikaya <>, Christian Huitema <>, "" <>, 5GANGIP <>
Thread-Topic: [5gangip] ILA forwaring [Was Re: Problem Statement]
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Date: Tue, 01 May 2018 19:02:18 +0000
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Subject: Re: [Ila] [5gangip] ILA forwaring [Was Re: Problem Statement]
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You can't push routes to the Internet. ISP chose what they accept and whom they accept it from but typically nothing smaller than a /17 is allowed. Can we keep it real please!

-----Original Message-----
From: 5gangip <> On Behalf Of Tom Herbert
Sent: Tuesday, May 01, 2018 11:44 AM
To: Dino Farinacci <>
Cc: Tom Herbert <>;; Behcet Sarikaya <>; Christian Huitema <>;; 5GANGIP <>
Subject: Re: [5gangip] ILA forwaring [Was Re: Problem Statement]

On Tue, May 1, 2018 at 10:25 AM, Dino Farinacci <> wrote:
>> I will try to answer your questions in as much detail as possible.
> Thanks for more details.
>> Here are the example cases that illustrate operation.
>> Case #1: A network has a single SIR prefix and one ILA-R and some 
>> number of ILA-Ns. The ILA-Ns do not have a map cache and are only 
>> used for SIR to ILA transformation.
>> The ILA-R advertises the SIR prefix in normal IP routing. It is the 
>> router for the SIR prefix. Packets destined to an address with the 
>> SIR prefix are thus routed the to ILA-R. Mapping entries are realized 
>> as hosts routes in the ILA-R where the destination host is composed 
>> of the SIR prefix and identifier. When an ILA-R receives a packet it
> What do you mean by realized. Are host routes storedin ILR-R routers via a push protocol like ILAMP? You are going to push all host routes for all ILA-N nodes in the Internet?
That are host routes in the local ILA-R routing table.

>> * Note that none of these cases so far require a mapping cache. These 
>> work for all packets regardless of the source. The sender may be 
>> local to the network, or may be a host on the Internet.
> That is not clear for case #1. Answer my above question first.
>> Case 4: Map caches are enabled on ILA-Ns.
>> The map cache is implemented as host routes in an ILA-N similar to 
>> ILA-R routes. When a packet is sent by a downstream device (e.g. a 
>> UE) it traverses an ILA-N. The ILA-N performs a route lookup on the 
>> packet. If an ILA route is found (a map cache hit) an ILA 
>> transformation is performed an the packet is forwarded directly 
>> towards the destination. If there is no ILA route (map cache miss), 
>> then another route is found possibly the default route (remember 
>> these are just normal route lookups). The packet is forward per the 
>> route and since it still has a SIR prefix in the destination address 
>> it will be forwarded to an ILA-R as described in case #1. The ILA-N 
>> does not send a mapping request and does not remember the 
>> destination, it just forwards without incurring any additional delay.
> Okay, so the scale of the underlay depends on the number of SIR prefixes injected into the routing system. When using sharding, it could be a lot. This model is kinda a hybrid overlay/underlay where the underlay needs to take part in make packet forwarding work. So be it.

Yes. It's already common technique with things like load balanceres that on routing to distribute packets.

> Dino
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