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

Tom Herbert <> Tue, 01 May 2018 19:13 UTC

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From: Tom Herbert <>
Date: Tue, 01 May 2018 12:13:08 -0700
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Cc: Dino Farinacci <>, Tom Herbert <>, "" <>, Behcet Sarikaya <>, Christian Huitema <>, "" <>, 5GANGIP <>
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Subject: Re: [Ila] [5gangip] ILA forwaring [Was Re: Problem Statement]
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On Tue, May 1, 2018 at 12:02 PM, FIGURELLE, TERRY F <> wrote:
> 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!
We are not pushing route to the Internet. ILA in internal to a site.

> -----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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