Re: [mdnsext] The Scope Swamp: Wireless Considerations

"Bhavik Fajalia (bfajalia)" <bfajalia@cisco.com> Wed, 07 August 2013 03:50 UTC

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From: "Bhavik Fajalia (bfajalia)" <bfajalia@cisco.com>
To: "Yi Yang (yiya)" <yiya@cisco.com>, Alf Watt <alf.watt@ruckuswireless.com>, "mdnsext@ietf.org" <mdnsext@ietf.org>
Thread-Topic: [mdnsext] The Scope Swamp: Wireless Considerations
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Date: Wed, 7 Aug 2013 03:50:36 +0000
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Subject: Re: [mdnsext] The Scope Swamp: Wireless Considerations
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I agree with this. You might want to go through the draft
:http://tools.ietf.org/html/draft-bhandari-dnssdext-mdns-gateway-01
Which mentions how wireless is different from wired and what are the
optimisations needed for wireless network.

Apart from scope, we need to worry about the the amount of mDNS traffic
goes to wireless clients,
it would not only impact the shared bandwidth but also battery power of
the wireless devices.

Regards,
Bhavik

On 07/08/13 1:19 AM, "Yi Yang (yiya)" <yiya@cisco.com> wrote:

>I agree we must consider difference between wired/wireless networks.
>
>Actually, even for a smaller scope, multicast over 802.11 is still an
>expensive operation.
>
>On the other hand, we should de-couple discovery scope from
>broadcast/multicast domain.
>
>Yi
>
> 
>
>On 8/5/13 5:47 PM, "Alf Watt" <alf.watt@ruckuswireless.com> wrote:
>
>>Following up from the BoF discussion in Berlin today on scoping of
>>service
>>advertisements.
>>
>>The discussion of scope needs to acknowledge the difference between wired
>>and wireless networks.
>>
>>In all IP networks the size of the broadcast domain is a fundamental
>>limitation, as the number of devices on the link increases the broadcast
>>traffic begins to consume a larger and larger percentage of the available
>>bandwidth. Traditionally large wired networks were segmented along
>>physical lines, by floor or wing, for example, with each area being
>>assigned a subnet and routed to provide end-to-end connectivity.
>>
>>Wi-Fi users expect (and the 802.11 protocol requires) that users on a
>>single SSID are connected to the same IP network and broadcast domain so
>>that they can roam seamlessly anywhere within a particular ESS (which can
>>be a building, campus or metro area). Limiting the size of these
>>broadcast
>>domains means separating users onto different Wi-Fi networks depending on
>>their role, instead of their location.
>>
>>So for wired networks we have a natural, physical scope depending on the
>>physical connection of hosts, in wireless networks we have scopes which
>>depend largely on the users access rights (since Wi-Fi is almost always
>>the security demarkation in networks).
>>
>>It¹s also worth nothing that the BCP for broadcast domain size is only
>>255
>>hosts (a /24) which makes the 802.11 ESS requirement for a single
>>broadcast domain behind a given ESS difficult to achieve for large
>>networks, which is why many Wi-Fi vendors support multicast filtering,
>>client isolation and ARP proxies all of which can impact mDNS usability.
>>
>>Best,
>>Alf
>>
>>FYA http://www.youtube.com/watch?v=-FizhXOW2VM&noredirect=1
>>
>>
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