Óscar gonzález de dios pce, the magic component of segment routing telefónica i+d
TRANSCRIPT
3ÁreaCompany Name
Running a packet-based Network
• Two main philosphies to operate a packet-based network Keep my life simple
• Let the routing decide the path, and let the network distribute the labels I want control, I am smart
• Let me decide where my traffic goes
• Problems of “Keep my life simple” approach The good old times of free unlimited bandwidth are gone Difficult to use several paths Difficult to differentiate among traffics
• OK, so I need to have more control over my traffic Traffic Engineering RSVP-TE allows to set up explicit tunnels and send traffic through them
• Great… but … TE comes with increased complexity Traffic Engineering with RSVP-TE needs lots of tunnels.
4ÁreaCompany Name
What do we need?
Simplification
1
Scalability
Adapat to changes
3
• Less state in the network
• Less state in the router
• Less tunnels maintained
• No need to signal new paths
• Apply Fast Reroute easily
• Less Protocols in the routers
• No RSVP-TE, no LDP, no T-LDP
2
5ÁreaCompany Name
Principle of Segment routing
• “Segment Routing enables any node to select any path (explicit or derived from Interior Gateway Protocol (IGP) Shortest Path Tree (SPT) computations) for each of its traffic classes”. (*)
• Let’s identify uniquely “segments” in the network
• At the source, add to the packet the list of segments as labels
• With a simple label lookup at each hop, the packet reaches the destination
(*) http://tools.ietf.org/html/draft-previdi-filsfils-isis-segment-routing-02
6ÁreaCompany Name
Benefits
• Uses existing MPLS hardware (I hope)
• Maintains few state in the devices (just the forwarding table) Lower CPU/memory requirements in network nodes
• Does not need to maintain tunnels Less complex to operate
• Easy to test any path Allows easy testing
8Core Networks EvolutionTelefónica I+D
SPRING Use cases
• CoS-based Traffic Engineering
• Deterministic non-ECMP Path
• Load-balancing among non-parallel links
• Fast Reroute
• Capacity Planning
• OAM
9Core Networks EvolutionTelefónica I+D
CoS-based Traffic Engineering: Example
• There are two main connections from US to Europe: High-capacity, no QoS
requirements and cheap. Low-capacity, minimum delay
and expensive.
• Expensive connections are used for Internet traffic, while cheap connections sends VoIP traffic from VPNs.
• Nowadays there is a manageability problem.
Internet Traffic
VPNs (VoIP)
10Core Networks EvolutionTelefónica I+D
Load-balancing among non-parallel links + Deterministic non-ECMP Path: Example
• Telefonica International Network
• Multiple links between the peering points and Miami.
• The same from Miami to the different countries.
• RSVP-TE can not be used because of the multiple combinations of links for a two hops path enabling load balancing. Segment Routing would enable this
easily.
• To differentiate services, ECMP is not enough Explicit Path
Miami
Peering Points
Brasil
ArgentinaChile
Peru
Ecauador
11Core Networks EvolutionTelefónica I+D
Capacity Planning Process
• Segment Routing offers a simple support for explicit path policy.
• One node segment represents the set of ECMP-aware shortest paths.
• Adjacency segments allow to express any explicit path.
• The combination of node and adjacency segment allows to express any path without having to enumerate all the ECMP options.
12Core Networks EvolutionTelefónica I+D
OAM
• Remote bundle MS sends a packet to R1 which has a rule with
these segment list: {72, 662, 992, 664}
• Remote peering link Node A can monitor the dataplane liveness of
the unidirectional peering link from C to D of AS2 by sending an IP probe with destination address A and segment list {101, 9001}.
• Note: C Node-SID is 101 and C is connected to a peer D with external adjacency segment 9001
Miami
Peering Points
Brasil
ArgentinaChile
Peru
Ecauador
14ÁreaCompany Name
PCE: the magic component for segment routing
• Segment routing alone does not solve all your problems
• How do I get the list of segments for a path with contraints? PCE is the answer
• How do I optimize the whole network? PCE does it for you
• If there is less state in the network… where is the state? In the PCE It will keep the TED, the labels and the list of paths
• So… all the fuss about segment routing… but without a PCE
A Network with Segment routing without PCE is complex to operate
16ÁreaCompany Name
The recipe: PCE for segment routing
• PCEP to query with constraints/inclusion/exclusion
• Syntax to express a SR path (e.g. SR-ERO)
• Stateful PCE to keep track of paths
• Active PCE to create automatically fast reroutes
• Active PCE to reoptimize network
• PCEP for remote instantiation
17ÁreaCompany Name
Conclusions
• Segment Routing allows to remove complexity from the network devices
• SR enables traffic engineering
• PCE complements Segment Routing Maintains network state Computes optimum paths Takes into account constraints in computation Active stateful PCE can control a network with segment routing