Chair of Network Architectures and Services Department of Informatics Technical University of Munich Source Packet Routing in Networking (SPRING) Adrian Reuter January 30, 2017 Chair of Network Architectures and Services Department of Informatics Technical University of Munich
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Contents Introduction SPRING Working Group Alternative Source Routing Solutions Comparison Conclusion Adrian Reuter – SPRING 2
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Internet Topology Adrian Reuter – SPRING 3
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Routing Information Base Destination Network mask Gateway Interface Metric 192.168.0.0 255.255.255.0 0.0.0.0 eth0 1000 192.168.1.0 255.255.255.0 0.0.0.0 eth1 1000 169.254.0.0 255.255.255.0 192.168.1.1 eth1 1000 0.0.0.0 0.0.0.0 192.168.0.1 eth0 600 Standard strategy: • Shortest Path First • found in RIB by Longest Prefix Match ⇒ Every router decides on its own where to route a packet Adrian Reuter – SPRING 4
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Source Routing Source imposes the route to be taken towards the destination A source route can be both types: • loose: specifying a set of nodes to be traversed • strict: an explicit and complete path through network topology A source route can be established either by: • per-flow states maintained on intermediate nodes • routing information attached to packets Adrian Reuter – SPRING 5
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Why Source Routing ? ⇒ Source routing increases network programmability Adrian Reuter – SPRING 6
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Outline Introduction SPRING Working Group Alternative Source Routing Solutions Comparison Conclusion Adrian Reuter – SPRING 7
Chair of Network Architectures and Services Department of Informatics Technical University of Munich SPRING working group IETF has formed a working group addressing Source Packet Routing in Networking (SPRING) • chartered to • identify source routing use cases • define requirements for source routing enabled networks • develop a new source routing mechanism • developed a new source routing mechanism: Segment Routing • in final stage: preparing final document revisions Adrian Reuter – SPRING 8
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Segment Routing (SR) • source route is encoded as a list of Segments • a segment represents "an instruction a node executes on the in- coming packet" [1] • Three types of segments: • IGP-Node Segment • IGP-Prefix Segment • IGP-Adjacency Segment • segments are advertised within the segment routing domain by the Interior Gateway Protocol (IGP) in use Adrian Reuter – SPRING 9
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Node Segment • uniquely identified within SR-domain by an Segment Identifier (SID) • each node is assigned a SID • all nodes within SR-domain install an entry for the segment in their Forwarding Information Base (FIB) • a node is reached by the shortest path determined by the IGP algorithm Adrian Reuter – SPRING 10
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Prefix Segment • nodes advertise the network prefixes they are attached to • each prefix is identified by a SR-domain-wide unique SID • handled and forwarded the same way as node segments But: Prefix segments are only advertised by those nodes that are attached to the respective (sub)network Adrian Reuter – SPRING 11
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Adjacency Segment • allows packets to be steered along specific links • nodes assign a SID to each unidirectional link with node-locally scope only • all nodes within SR-domain install an entry for the adjacency segment in their Routing Information Base (RIB) ⇒ entry in FIB only at advertising node Adrian Reuter – SPRING 12
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Example: Node and Adjacency Segments Adrian Reuter – SPRING 13
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Implementation via MPLS • label-based switching instead of IP-based longest prefix match • a label assigns a packet to a Forwarding Equivalence Class (FEC) ⇒ packets of a FEC have "the same forwarding treatment" [2] • border routers of a MPLS domain add label(s) to incoming packets ⇒ list of SIDs are encoded as MPLS label stack Adrian Reuter – SPRING 14
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Implementation via IPv6 • new routing extension header of type 4: Segment Routing Header (SRH) • SIDs are encoded as IPv6 addresses • original incoming IP datagram is encapsulated with an outer IPv6 header (and its SRH) • currently active SID is the dest. address of the outer header Adrian Reuter – SPRING 15
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Segment Routing Header (SRH) 0 8 16 32 24 Routing Type Segments Left Next Header Hdr Ext Len First Segment Flags HMAC Key ID Segment List[0] (128 bits ipv6 address) ... Segment List[n] (128 bits ipv6 address) Policy List[0] (optional) ... Policy List[3] (optional) HMAC (256 bits) (optional) Adrian Reuter – SPRING 16
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Outline Introduction SPRING Working Group Alternative Source Routing Solutions Comparison Conclusion Adrian Reuter – SPRING 17
Chair of Network Architectures and Services Department of Informatics Technical University of Munich IPv6 RH0 Extension Header • routing extension header of type 0 • allows to specify a list of arbitrary non-multicast IPv6 addresses • all addresses need to be transitted before reaching final dest. • deprecated by IETF due to security concerns: DoS attacks with high efficiency : routing packets back and forth Adrian Reuter – SPRING 18
Chair of Network Architectures and Services Department of Informatics Technical University of Munich IPv6 RH0: DoS Exploit Adrian Reuter – SPRING 19
Chair of Network Architectures and Services Department of Informatics Technical University of Munich MPLS with RSVP or LDP • up to now: method of choice for traffic engineering by source routing • mostly used in service provider networks • dedicated protocols to communicate label meanings: LDP , RSVP • one label-switched path for each unidirectional flow Adrian Reuter – SPRING 20
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Routing Protocol for Low-power and Lossy Netwoks (RPL) • based on distance-vector algorithm • idea: reduce routing complexity for low-power • IPv6 routing extension header of type 3, encapsulation in outer IPv6 header • only strict hop-by-hop source routing Adrian Reuter – SPRING 21
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Dynamic Source Routing (DSR) Protocol • designed for wireless ad hoc networks • selforganizing and selfadapting to topology changes • supports high node mobility • on-demand route discovery • various versions and extensions: SDSR, ESDSR, RMPSR ... Adrian Reuter – SPRING 22
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Outline Introduction SPRING Working Group Alternative Source Routing Solutions Comparison Conclusion Adrian Reuter – SPRING 23
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Comparison IPv6 RH0 not included in this comparison due to its official deprecation Adrian Reuter – SPRING 24
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Outline Introduction SPRING Working Group Alternative Source Routing Solutions Comparison Conclusion Adrian Reuter – SPRING 25
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Conclusion Segment Routing ... • is likely to become a key technology for optimizing traffic flows in large-scale networks • shows potential for an universal standard for source routing • experiences broad support by industry (Cisco, Nokia, Juniper, ...) • will an appealing target for network hackers Adrian Reuter – SPRING 26
Chair of Network Architectures and Services Department of Informatics Technical University of Munich [3] Adrian Reuter – SPRING 27
Recommend
More recommend
