Re: [OSPF] [spring] draft-psenak-ospf-segment-routing-extensions-05

[Peter Psenak <[e-mail]>]

Anil,

Adj-SID is a link attribute. Link is identified the same way as it is 
identified in the Router LSA - link-type, link-id, link-data.

for unnumbered link:

link-type = 1
link-id = Neighboring router's Router ID
link-data = interface's ifIndex

So if RTA wants to use a particular link between RTB and RTC, it needs 
to know the ifIndex of that link and pick the link based on that.

regards,
Peter

On 2/2/15 15:39 , Anil Kumar S N (VRP Network BL) wrote:
> Hi All,
>
>       I have a question on Adjacency Segment Identifier:
>
> How will RTA indentify and map adj-labels originated by RTB (having
> unnumbered point-to-point connections b/w RTB and RTC) among labels to
> which link ?
>
> Router ID
>
> 1.1.1.1            2.2.2.2                     3.3.3.3
>
>                     +-------+  P2p Links 1-5   +-------+  
>
>                     |       +-------------+----+       |
>
>                     |       |                  |       |
>
> +-------+          |       +------------------+       |
>
> |       |          |       |                  |       |
>
> |  RTA  +----------+  RTB  +------------------+  RTC  |
>
> |       |          |       |                  |       |
>
> +-------+          |       +------------------+       |
>
>                     |       |                  |       |
>
>                     |       +------------------+       |
>
>                     |       |                  |       |
>
>                     +-------+                  +-------+
>
> Router vertex 2.2.2.2
>
> LinkType  LinkId          LinkData        Metric  IfIndex  IfType
>
> P2P       1.1.1.1         11.0.0.112      100     0        NULL
>          >> Connected to Nbr vertex 1.1.1.1
>
> P2P       3.3.3.3         12.0.0.112      100     0        NULL
>          >> Connected to Nbr vertex 3.3.3.3
>
> P2P       3.3.3.3         13.0.0.112      100     0        NULL
>          >> Connected to Nbr vertex 3.3.3.3
>
> P2P       3.3.3.3         14.0.0.112      100     0        NULL
>          >> Connected to Nbr vertex 3.3.3.3
>
> P2P       3.3.3.3         15.0.0.112      100     0        NULL
>          >> Connected to Nbr vertex 3.3.3.3
>
> P2P       3.3.3.3         16.0.0.112      100     0        NULL
>          >> Connected to Nbr vertex 3.3.3.3
>
> Quick Reference RFC 2328 A.4.2 Router-LSAs [Link Type]
>
> Type
> A quick description of the router link. One of the following.
> Note that host routes are classified as links to stub networks
> with network mask of 0xffffffff.
>
> Type Description
> __________________________________________________
> 1 Point-to-point connection to another router
> 2 Connection to a transit network
> 3 Connection to a stub network
> 4 Virtual link
>
> Link ID
> Identifies the object that this router link connects to. Value
> depends on the link's Type. When connecting to an object that
> also originates an LSA (i.e., another router or a transit
> network) the Link ID is equal to the neighboring LSA's Link
> State ID. This provides the key for looking up the neighboring
> LSA in the link state database during the routing table
> calculation. See Section 12.2 <#Title_12.2>for more details.
>
> Type Link ID
> ______________________________________
> 1 Neighboring router's Router ID
> 2 IP address of Designated Router
> 3 IP network/subnet number
> 4 Neighboring router's Router ID
>
>
> Link Data
> Value again depends on the link's Type field. For connections to
> stub networks, Link Data specifies the network's IP address
> mask. For unnumbered point-to-point connections, it specifies
> the interface's MIB-II [Ref8] <#BibRef_Ref8>ifIndex value. For the other
> link
> types it specifies the router interface's IP address. This
> latter piece of information is needed during the routing table
> build process, when calculating the IP address of the next hop.
> See Section 16.1.1 <#Title_16.1.1>for more details.
>
> With Regards
>
> Anil S N
>
>
>
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