Re: [Anima-signaling] Take 2: Draft message on proposed change to GRASP

["Joel M. Halpern" <[e-mail]>]

The proposal looks fine.  I might adjust the "implementation" text 
slightly.  If someone implements multiple ASAs in a common address 
space, they can share the UDP port and demux using other fields.  This 
change allows them to be in separate spaces, without requiring it.

What I am commenting on the text "When it starts up, an ASA will ...". 
I think "will" is too strong.

Yours,
Joel

On 4/27/16 7:52 PM, Brian E Carpenter wrote:
> Hi,
>
> Design team, and Joel,
>
> Updated following the feedback received and trial implementation. Please
> let me know if OK; I would like to send this to the WG tomorrow.
>
> Short version:
>
> We propose that when an ASA listens for negotiation or synchronization
> requests, it should do so on its own transport port number rather than sharing
> the generic GRASP port number as currently defined. The consequence for the
> protocol is that discovery responses must include a complete transport address
> (locator+protocol+port) instead of just the locator.
>
> Long version:
>
> We want ASAs to run as separate modules in user address space, as applications,
> rather than being bundled with the GRASP engine in kernel space. To achieve this
> with all ASAs listening on the same port number would require quite complicated
> inter-process communication between the GRASP kernel and the indvidual ASAs.
> The details of this would be different in every operating system. If we
> allow each ASA to have its own port this can be avoided, and each ASA can have
> its own copy of the GRASP API library if required. This will make the systems
> engineering of portable ASAs much easier, and will make the adaptation of
> the GRASP API library and the GRASP kernel to various operating systems easier
> too.
>
> In practice we need to indicate the protocol (TCP or UDP) as well, since
> dynamic ports are assigned for a specific socket and protocol.
>
> We propose to redefine the locator returned by GRASP discovery accordingly. For
> the IPv6 case that would give the following CDDL:
>
> locator-option /= [O_IPv6_LOCATOR, ipv6-address, transport-proto, port-number]
> ipv6-address = bytes .size 16
> transport-proto = IPPROTO_TCP / IPPROTO_UDP
> IPPROTO_TCP = 6
> IPPROTO_UDP = 17
> port-number = 0..65535
>
> We did consider making this optional, but that would raise interoperability
> issues. If an implementation does choose to use the GRASP_LISTEN_PORT
> for all ASAs, that could simply be returned as the port-number.
>
> Implementation note:
>
> When it starts up, an ASA will obtain an ephemeral port number for each
> transport protocol that it supports, and that will be used in discovery
> responses.
>
> Comments?
>
> Note: Toerless Eckert brought up this problem and outlined the proposed
> solution.
>
>     Brian
>
>
>