-----Original Message----- From: homenet [mailto:homenet-boun...@ietf.org] On Behalf Of STARK, BARBARA H Sent: Monday, July 27, 2015 4:50 PM To: homenet@ietf.org Subject: [homenet] some IS-IS questions
>Given some of the discussion last week, I found that I had some questions >about what is or isn't already defined somewhere within the set of IS-IS specs >*and* is already implemented in a load suitable >for a homenet router. I've >read the Babel specs, so I have a good idea of what's in Babel. Plus there was >that really good Babel presentation Thursday night. But I'm having real >trouble finding the right IS->IS specs to answer my questions. >There was a claim that IS-IS provides "diagnostics". >What sort of diagnostics? http://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k_r43/routing/configuration/guide/b_routing_cg43xasr9k/b_routing_cg43xasr9k_chapter_01011.html#concept_B475330101904631B14C625066A033C3 Search at the above URL for " Route Convergence Monitoring and Diagnostics". >Is this a reference to topology discovery? Does topology discovery rely on >device participation in IS-IS, or can devices that do not participate in IS-IS >be discovered? All devices in the IS-IS domain need to be routers. Neighboring routers find each other by exchanging Hellos using multicast. Loosely speaking, an IS-IS router uses link-state packet (LSP) to flood learnt prefixes and topology to neighbors. IS-IS supports both IPv4 and IPv6 easily. >Can bridged devices be discovered? Yes/No. The bridge would need to be a RBridge such as in TRILL and then the bridge can be discovered. Or if the bridge is connected to an IS-IS router or a switch connected to the IS-IS router, the router/switch can learn the end bridged device mac-address. The learnt mac-address can be propagated to IS-IS using a sub TLV in IS-IS. > If yes, can they be discovered even if they don't do IS-IS? If yes, how does > that work? See above. >Can physical layer topology be discovered? IS-IS knows who its neighbors are and also knows the path to any other neighbor. Wouldn't this suffice? Or please give an example of a physical layer topology that the network layer is not able to provide. >What additional diagnostics outside of topology discovery does IS-IS support? See the URL I mentioned above. >I was told that IS-IS can help avoid loops caused by bridged interfaces as >well as routed interfaces? Is this correct? Not quite. When IS-IS was added to RBridges by TRILL, it is the TRILL header that includes a Hop count that helps avoid routing loops, not IS-IS. IS-IS is a connection-less protocols and thus a TTL (or hop count) in the IPv4 header cannot be leveraged to avoid loops. IS-IS avoid loops as soon as the new network topology is flooded to all the routers within the routing area. >If yes, does it rely on participation of bridges in IS-IS, or can it be done >with only participation by routers? See above. >I was told that with IS-IS a "service provider" router could somehow >automatically take control of QoS and routing policy in the network, and >dictate policy to other routers (assuming the other routers >even have a QoS >policy). Is this true? How does this work, especially if there are multiple >"service provider" routers? Would this be in the IS-IS version suitable for >homenet? The home router does not include the WAN interface in LAN routing whether the routing is IS-IS or another routing protocol. Then IS-IS only operates in the home LAN. I defer to others to signaling QoS with IS-IS or taking over routing policy. IS-IS is flexible and adds new functionality in a jiffy using TLV option and sub-TLV options. >I was told that if IS-IS is selected, hosts will be able to do resource >reservation across the homenet. Resource reservation has yet to be implemented >in unmanaged home network devices, though many >standards have been written. >In general, the complexity of supporting resource reservation schemes has >never been worth the cost. Is this something that will suddenly work as a >result of IS-IS >implementation in routers? Is it in the IS-IS subset proposed >for homenet? What does it require in the hosts? IS-IS has no implication on hosts. Resource reservation using RSVP is performed for QoS in the Internet. IS-IS runs in the LAN. Hemant _______________________________________________ homenet mailing list homenet@ietf.org https://www.ietf.org/mailman/listinfo/homenet
