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11.Basic Knowledge of MPLS and SR Layer 2.5 - Coggle Diagram

- - - - MPLS VPN App
        
        basic Concepts and working principle of MPLS
        nowdays bicuz of the performance of the SWs Routers > are very good > we dont Need the MPLS tp help us to speed up the data forwarding / bicuz its same speedeven if we use the IP forwarding
        (CustomersHQ)VPN[CE Router(BranchOfCustomer)]<>(ISP)MPLSDomain[PE and P Routers]<>[CE Router]VPN(CustomersHQ)
        
        so now MPLS will be used in VPN application >MPLS VPN
        in the MPLS Domain > it always be the ISP where we have diffrent customers which have the requirments to communicate with their remote sites through the ISP through the internet soo they will purchase the MPLS from the ISP
        and we can use MPLS VPN to destinguish diffrent enterprises and VPNs
        
        MPLS TE Traffic Engine App
        with this tech we can control the traffic to go to use the diffrent paths , to use diffrent links
        diffrent Routes (for eample using some kind of a certralised Net) Controlled by the TE depending on links bandwidtch and reliability (larger links willl be te primaru links) which will take the bigger perccentage of the traffic > the rest is for secondary links
      - Traditional IP forwarding
        search the IP routing table and use longest mask match to find the destination and to find next hop
        Forward it to the Next hop
        same thigs for next Hops until Final Destination
        performancce of the Physical equipment is limited and IP routing table is very large >> increase the processing time of the pysical Equip
        anf For that we Introdduce the ATM cell Forwarding
      - ATM AsynchronousTransferMode cell Forwarding
        in the ATM table we dont have to care about all the destination Nets cuz packets may want to go different destinations - table dosent have to be maintained
        we just have to maintain the table with the label which helps to go to next hop > reducing the size of the table and very simple forwarding >> speding up data forwarding
      - MPLS Label Forwarding
        host <> MPLSDomain[Routers] <> oterRouters <> Host
        is like putting the IP forwarding and ATM together
        we use label to forward the data and if data have an IP header > well add new header > MPLS Header
        in MPLS Domain we dont have to check the ip header or the routing table to forward the data >> we only need the MPLS Header that contain the labels soo well only to have to search the in the MPLS label table to find the next hop [swap labls <> ingoing label >> associated outgoing label] > and forward the data >>> MPLS Lable Forwarding
        last hop in the MPLS domain >> hop remove the MPLS header and send to destination
    - - MPLS Label Format
        
        Frame Mode MPLS
        MPLS have 2 encapsulation modes
        
        cell mode
        ATM uses the MPLS cell encapsulation mode which is no t involved in this course
        
        Frame mode
        
        in the frame encapsulation mode an MPLS label header is added btw the Layer 2 header and layer 3 header of a packet
        Ethernet and PPP uses the Encapsulation Mode
        
        traditional Layer 2 Frame format
        
        IP Header
        
        Payload
        
        Frame Header
        
        MPLS Frame mode encapsulation
        
        IP Header
        
        MPLS Header - 32 bits
        
        EXP - EXP Use - 3bits
        
        S - Bottom of Stack - 1 bit
        cuz MPLS Supp multiple MPLS headers we need a way to know the Bottom the Stack - 1 for last Header / 0 not yet
        
        TTL - 8 bits
        used to prevent the loop - TimeToLive
        
        LABEL - 20 bits
        
        Frame Header
        
        Payload
        
        MPLS Label Nesting
        
        We know that we can have Multiple MPLS Headers - it supports Netsting
        
        Apps of Label Nesting
        
        2 more items...
      - MPLS Forwarding Process
        
        FEC and NHLFE
        
        FEC - Forwarding Equivalence Class
        set of data flows with certain common characteristics. Theses data flows are processed by LSR in the same way during the following Process
        FEC can be classified based on the address serviceType and QoS. For example, in the traditional IP forwarding that uses the longest matching algo, all packets to the same route are an FEC
        
        NHLFE Next Hop Label Forwarding Entry
        the NHLFE is used for label forwarding
        it contains the following basec info
        next hop of the packet
        how to preform a tag operation (including pushing a new tag popping a tag and swapping the original tag with a new tag)
        the NHLFE may contain other information, such as link layer encapsulation used for sending packets
        Example
        [RT]>display mpls 1sp include 10.2.0.0 24 verbose
        
        MPLS Forwarding
        
        Ingress Forwarding LER - 1st Router
        
        MPLS Forwarding - LSR (middle Routers)
        on the Transit node < the ILM IncomingLabelMap table and NHLFE table are quired to uide MPLS packet forwarding
        
        Egress Forwarding LER - last Router
        on the Egress node > the ILM table is quired to uide MPLS forwarding
      - MPLS control Plane and Forwarding Plane
        
        MPLS Network Model
        IP Net <> MPLSDomain[LR[RouterA] <> LSP / LSR <> LER[RouterD]] <> IP Net
        all Routers inside MPLS Somain are running MPLS PProtocol
        in this Domain we have several roles
        
        LER Label Edge Router
        in this Net we havve 2 LERs > Router A and Router D > they are at the edge of the MPLSDomain
        when we give our ip packet to the MPLS Domain to the LER > The LER oushes a label to this packet and when this ppacket is Forwarded in the MPLS Domain it will always be with a label
        
        LSR Lable Switch Router
        all the other Routers in te mdddle are are LSR Routers
        
        LSP Label Switch Path
        LSP is called a tunnel
        The path from the Source to the destination from RouterA to RouterD LERs > we call it LSP
        
        MPLS control Plane and Forwarding Plane
        
        Control Plane
        
        IP Routing Table
        IP routing table can help us to builf the IP forwarding Table
        we can regard the IP routing table and IP forwarding table as the same thing in diffrent planes
        
        Label Distribution Protocol
        we need to build the Label Forwarding Table
        bicuz in the MPLS Domain we dont wanna use the IP routing table but theLabel Forwarding table to find the Outgoing label for each hop
        
        Routing Prtocol
        help us to calculate Routes and to build the IP routing table
        
        Data/FForwarding Plane
        
        1st hop(or gate) [LER] in the MPLS Domain we recv an Incoming ip packet to (LER)
        Edge Router will recv the IP packet > then well search the IP forwarding table > there will be 2 situations
        
        this IP packet dosent have to go to the MPLS tunnel[LSP] > and it will be traditional IP forwarding NO MPLS SHIT
        
        ip packet needs to o to the tunnel (destination addres is the tunnel) and we have to give to this tunnel > push an mPLS header to this packet > and forward to it
        
        next Hop in the Tunnel Case is the LSR
        LSR recv the incoming labeled packet and then it will search the incoming Label in the label forwarding table nad it will have 2 situations
        
        if the LSR is in the middle of other LSRs > well simply swap outgoing and incoming labels and forward the packet to next hop
        
        LSR is in the edge meaning that its an LER not LSR >> we fing no incoming label matching to the incoming label we need to pop the MPLS header nd then continue to process the IP header and forward this packet outside the tunnel based on the IP routing table
- - - - Problems Faced By RSVP
        RSVP creates an end2end LSP hop by hop based on the CSPF path calculation result. The label is a local label
        HopByHop , traversing nodes maintain the status of the tunnel. Even if SDN is used > the Tunnel Status needs to be maintained
        RSVP TE configuration is complex
        Complex ECMP implementation
        8 Types of RSVP protocol packets occupy nettwork bandwidth and CPU processing
        RSVP is complex in load balanciong and needs to be configred with multiple tunnels which brings huge workload to configs and maintenance
      - Problems Faced By LDP
        we know in MPLS we have several protocols that help us to distribute the labels and LDP is one of them
        LDP depends on IGP and uses local switching to support ECMP(thats based on local label switching to support equal cost mulltiple path)> that means if we wanna run LDP we have to first run IGP protocols such as OSPF or ISIS > they mustve learned the routing table then use LDP to distribute the labels
        Disadvantages >
        LDP has 11 types of protocols packets which greatly increase link bandwidth consumption and device CPU usage
        LDP supports only the shortest IGP path *min cost( for path calculations .TE(TrafficEngineering) is not supported
    - - SR Technology
        
        Incremental SDN Net
        which is this Course Topic > SegRouting
        for this Net the existing Protocols can be expanded to achieve better smooth evolution >> soo we dont need to seperate all the control plane and forwarding planes on the Controller and NetDevice >> Controller can have part of the control planes and also the other parts of the control planes can still be on the Net Device providing the balance between centralized contro and distributed deployments
        for that it uses the Seg routing technology to provide fast interaction between the Net and upper layer applications >>> SR
        
        Revolutonary SDN Net
        Net faults in the can be rectified only when the Controller if faulty / reliability is very poor
        we use the controller as new device to seperate the forwarding plane and the control plane > control plane does not need to work on the Net device | all the control plane is working on the controller and we only need to use the Net device to forward the data and all the tables including the routing table , MPls table
        all tables are calculated and working on the controller requiring very high preformance unlike the NetDevice where we no longer need huge ressources
        But still this kind og the Net is a subVersion of the traditional Nets and not support by equipment vendors and carriers sooo for the reason INcremental SDN Network is created
        
        Traditional Net
        Control Plane + Forwarding Plane
        in Traditional Net > Control Plane and Forwarding Plane are integrated on the Network Devices
        require very high preformance of the Net Device
    - - Control Plane
        
        Routing P Extenscion - ISIS/OSPF/BGP
        
        SDN Controller - BGP_LS/PCEP/NetConf
      - Data-Forwarding Plane
        
        MPLS-SegmentLabel
        
        IPv6 - SRH Extended Header
      - Path Selection
        
        Path Computation - SPT Computation
        
        Explicit Path - Segment List
  - - - Segment
        
        An instruction that a node(Router) executes on an ingress packet
        node>oneRouter is Node | prefix>going to some dest ip > theDestination is a prefix | adjecent>we can regard it as the path
        
        Adjency Segment> Dynamically allocated by source nodes through protocols
        
        Prefix Segment> Manually configured
        
        Node Segment> Manually configured
      - SID
        
        SegID > Seg Routing Defines the destination address Prefix / Node and adjacency on the net as a seg and assigns sed IDs to these destination address prefixes / nodes abd adjencies
      - SR Domain
        
        Segment Routing Domain < indicates the set of SR nodes
      - SRGB
        
        Seg Routing global Block > local tag set reversed for a global segment. im MPLS > SRGB is a set of local labels reserved labels
      - Segmet List
        
        a sort of a set of dsetination prefix SID / node SID and adjacent SID ordered list > used to identify a complete label switching path LSP(Label Switched Path) in the MPLS architecture > segList is encapsulated in the packet header to guide forwarding