Routing inter-AS LSPs with centralized controller

1. A method comprising:

receiving, by a network device within a first autonomous system (AS), inter-AS traffic engineering (TE) metric values for one or more inter-AS links that indicate route preferences for routes between the first AS and a second AS;

storing the inter-AS TE metric values in a traffic engineering database (TED) of the network device;

sending, by the network device and to a centralized controller device coupled to the first AS and the second AS, contents of the TED including the inter-AS TE metric values;

receiving, by the network device and from the centralized controller device, path information for an inter-AS label switched path (LSP) across the first AS and the second AS computed by the centralized controller device based on the contents of the TED, wherein the inter-AS LSP comprises a first portion through the first AS based on a first set of intra-AS TE metric values for the first AS, a second portion between the first AS and the second AS that includes a preferred one of the one or more inter-AS links as indicated by the inter-AS TE metric values, and a third portion through the second AS based on a second set of intra-AS TE metric values for the second AS; and

establishing, by the network device, at least the second portion of the inter-AS LSP using the preferred one of the one or more inter-AS links according to the path information.

2. The method of claim 1 , wherein the inter-AS TE metric values comprise one or more of local preference values for the one or more inter-AS links that indicate a preferred outgoing route for the first AS, multiple exit discriminator (MED) values for the one or more inter-AS links that indicate a preferred incoming route for the first AS, or an explicit route object (ERO) that indicates a specific route between the first AS and the second AS.

3. The method of claim 1 , wherein sending the contents of the TED comprises sending the inter-AS TE metric values included in the TED to the centralized controller device using a link state attribute of a border gateway protocol (BGP-LS).

4. The method of claim 1 , further comprising advertising the inter-AS TE metric values to other network devices within the first AS using a link state routing protocol of an interior gateway protocol (IGP), wherein the inter-AS TE metric values are carried in an Opaque link state advertisement (LSA) of an open shortest path first (OSPF) link state routing protocol.

5. The method of claim 1 , further comprising advertising the inter-AS TE metric values to other network devices within the first AS using a link state routing protocol of an interior gateway protocol (IGP), wherein the inter-AS TE metric values are carried in a link state packet (LSP) of an intermediate system to intermediate system (IS-IS) link state routing protocol.

6. A network device comprising:

a memory; and

one or more processors in communication with the memory and configured to:

receive inter-AS traffic engineering (TE) metric values for one or more inter-AS links that indicate route preferences for routes between a first autonomous system (AS) and a second AS, wherein the network device is within the first AS,

store the inter-AS TE metric values in a traffic engineering database (TED) of the network device,

send contents of the TED including the inter-AS TE metric values to a centralized controller device coupled to the first AS and the second AS,

receive, from the centralized controller device, path information for an inter-AS label switched path (LSP) across the first AS and the second AS computed by the centralized controller device based on the contents of the TED, wherein the inter-AS LSP comprises a first portion through the first AS based on a first set of intra-AS TE metric values for the first AS, a second portion between the first AS and the second AS that includes a preferred one of the one or more inter-AS links as indicated by the inter-AS TE metric values, and a third portion through the second AS based on a second set of intra-AS TE metric values for the second AS, and

establish at least the second portion of the inter-AS LSP using the preferred one of the one or more inter-AS links according to the path information.

7. The network device of claim 6 , wherein the inter-AS TE metric values comprise one or more of local preference values for the one or more inter-AS links that indicate a preferred outgoing route for the first AS, multiple exit discriminator (MED) values for the one or more inter-AS links that indicate a preferred incoming route for the first AS, or an explicit route object (ERO) that indicates a specific route between the first AS and the second AS.

8. The network device of claim 6 , wherein the one or more processors are configured to send the inter-AS TE metric values included in the TED to the centralized controller device using a link state attribute of a border gateway protocol (BGP-LS).

9. The network device of claim 6 , wherein the one or more processors are configured to advertise the inter-AS TE metric values to other network devices within the first AS using a link state routing protocol of an interior gateway protocol (IGP), wherein the inter-AS TE metric values are carried in an Opaque link state advertisement (LSA) of an open shortest path first (OSPF) link state routing protocol.

10. The network device of claim 6 , wherein the one or more processors are configured to advertise the inter-AS TE metric values to other network devices within the first AS using a link state routing protocol of an interior gateway protocol (IGP), wherein the inter-AS TE metric values are carried in a link state packet (LSP) of an intermediate system to intermediate system (IS-IS) link state routing protocol.

11. A method comprising:

receiving, by a centralized controller device coupled to a first autonomous system (AS) and a second AS, contents of a traffic engineering database (TED) of a network device within the first AS, wherein the contents of the TED include inter-AS traffic engineering (TE) metric values for one or more inter-AS links that indicate route preferences for routes between the first AS and the second AS;

storing the contents of the TED received from the network device within the first AS in one or more routing tables of the centralized controller device, wherein the one or more routing tables include contents of TEDs of a plurality of network devices within both the first AS and the second AS;

computing, by the centralized controller device, an inter-AS label switched path (LSP) across the first AS and the second AS based on the one or more routing tables including the inter-AS TE metric values, wherein computing the inter-AS LSP comprises:

computing a first portion of the inter-AS LSP through the first AS based on a first set of intra-AS TE metric values for the first AS,

computing a second portion of the inter-AS LSP between the first AS and the second AS that includes a preferred one of the one or more inter-AS links as indicated by the inter-AS TE metric values, and

computing a third portion of the inter-AS LSP through the second AS based on a second set of intra-AS TE metric values for the second AS; and

sending, by the centralized controller device and to the network device within the first AS, path information for the inter-AS LSP in order to instruct the network device to establish at least the second portion of the inter-AS LSP using the preferred one of the one or more inter-AS links.

12. The method of claim 11 , wherein the inter-AS TE metric values comprise one or more of local preference values for the one or more inter-AS links that indicate a preferred outgoing route for the first AS, multiple exit discriminator (MED) values for the one or more inter-AS links that indicate a preferred incoming route for the first AS, or an explicit route object (ERO) that indicates a specific route between the first AS and the second AS.

13. The method of claim 11 , wherein receiving the contents of the TED of the network device within the first AS comprises receiving the inter-AS TE metric values included in the TED via a link state attribute of a border gateway protocol (BGP-LS).

14. The method of claim 11 , wherein computing the second portion of the inter-AS LSP between the first AS and the second AS comprises:

selecting a preferred outgoing route for the first AS from a plurality of outgoing routes from the first AS to the second AS based on a local preference value as one of the inter-AS TE metric values; and

selecting a preferred incoming route for the first AS from a plurality of incoming routes to the first AS from the second AS based on a multiple exit discriminator (MED) value as another one of the inter-AS TE metric values.

15. A centralized controller device comprising:

a memory; and

one or more processors in communication with the memory and configured to:

receive contents of a traffic engineering database (TED) of a network device within a first autonomous system (AS), wherein the contents of the TED include inter-AS traffic engineering (TE) metric values for one or more inter-AS links that indicate route preferences for routes between the first AS and a second AS, wherein the centralized controller device is coupled to the first AS and the second AS,

store the contents of the TED received from the network device within the first AS in one or more routing tables of the centralized controller device, wherein the one or more routing tables include contents of TEDs of a plurality of network devices within both the first AS and the second AS,

compute an inter-AS label switched path (LSP) across the first AS and the second AS based on the one or more routing tables including the inter-AS TE metric values, wherein, to compute the inter-AS LSP, the one or more processors are configured to:

compute a first portion of the inter-AS LSP through the first AS based on a first set of intra-AS TE metric values for the first AS,

compute a second portion of the inter-AS LSP between the first AS and the second AS that includes a preferred one of the one or more inter-AS links as indicated by the inter-AS TE metric values, and

compute a third portion of the inter-AS LSP through the second AS based on a second set of intra-AS TE metric values for the second AS, and

send, to the network device within the first AS, path information for the inter-AS LSP in order to instruct the network device to establish at least the second portion of the inter-AS LSP using the preferred one of the one or more inter-AS links.

16. The centralized controller device of claim 15 , wherein the inter-AS TE metric values comprise one or more of local preference values for the one or more inter-AS links that indicate a preferred outgoing route for the first AS, multiple exit discriminator (MED) values for the one or more inter-AS links that indicate a preferred incoming route for the first AS, or an explicit route object (ERO) that indicates a specific route between the first AS and the second AS.

17. The centralized controller device of claim 15 , wherein the one or more processors are configured to receive the inter-AS TE metric values included in the TED of the network device within the first AS via a link state attribute of a border gateway protocol (BGP -LS).

18. The centralized controller device of claim 15 , wherein, to compute the second portion of the inter-AS LSP between the first AS and the second AS, the one or more processors are configured to:

select a preferred outgoing route for the first AS from a plurality of outgoing routes from the first AS to the second AS based on a local preference value as one of the inter-AS TE metric values; and

select a preferred incoming route for the first AS from a plurality of incoming routes to the first AS from the second AS based on a multiple exit discriminator (MED) value as another one of the inter-AS TE metric values.