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Versions: (draft-ietf-rtgwg-npmnrp) 00 01 02 03 04

Network Working Group                                           J.L. Lan
Internet-Draft                                                J.H. Zhang
Intended status: Informational                                    B.Wang
Expires: April 21, 2017                                         W.F. Liu
                                                                 Y.J. Bu
         National Digital Switching System Engineering and Technological
                                              Research Center, P.R.China
                                                                   X. Li
                      BEIJING UNIVERSITY OF POSTS AND TELECOMMUNICATIONS
                                                         October 20, 2016

         Node Potential Oriented Multi-NextHop Routing Protocol
                       draft-lanzhangwang-rtgwg-npmnrp-02


Abstract

   The Node Potential Oriented Multi-Nexthop Routing Protocol (NP-MNRP)
   bases on the idea of "hop-by-hop routing forwarding, multi-backup
   next hop" and combines with the phenomena that water flows from
   higher place to lower.  NP-MNRP defines a metric named as node
   potential, which is based on hop count and the actual link bandwidth,
   and calculates multiple next-hops through the potential difference
   between the nodes.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 21, 2017.




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Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3. Protocol operation  . . . . . . . . . . . . . . . . . . . . . .  5
     3.1. LFBs Network prefix information advertisement . . . . . . .  5
     3.2. Neighbor Node Discovery and Adjacency establishment . . . .  7
     3.3. Calculation of node potential value . . . . . . . . . . . .  8
     3.4. network event sensing . . . . . . . . . . . . . . . . . . . 10
     3.5. Update of the node potential  . . . . . . . . . . . . . . . 12
   4. Routing information base  . . . . . . . . . . . . . . . . . . . 14
   5. NP-MNRP packets format  . . . . . . . . . . . . . . . . . . . . 15
     5.1. Encapsulation of NP-MNRP packets  . . . . . . . . . . . . . 15
     5.2. Packet format . . . . . . . . . . . . . . . . . . . . . . . 15
   6. Informative References  . . . . . . . . . . . . . . . . . . . . 24
   7. Author's Address  . . . . . . . . . . . . . . . . . . . . . . . 24


1. Introduction

   The inspiration of this routing protocol comes from the natural water
   flow, which is a phenomenon of potential energy driven. Water flows
   through all feasible channels from high potential site to low
   potential site. If in every router all feasible next-hops for one
   certain destination can be found, then all the packets to that
   destination can be transferred in many paths.

   This routing protocol obeys the Internet philosophy of "hop-by-hop
   routing paradigm" and enhances it with "multiple feasible next-hops".
   That means protocol try to calculate multiple next-hops for each node
   and not find multi-path end to end. The forwarding direction of
   packets is constrained by routing metrics. Different packets to one



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   destination can be distributed into multiple next-hops in parallel,
   which can make full use of all feasible next hops, so that the link
   utility ratio is globally even.

   Compared with nature water flow phenomenon, the routing protocol
   defines a routing metric named as node potential in communication
   networks. Node potential is a parameter to measure the ability to
   transfer packets from one certain node to its destination. So the
   routing protocol is named as node potential oriented multiple next-
   hops routing protocol (NP-MNRP in short).

   NP-MNRP is designed to calculate multiple next-hops for one
   destination in network without knowing the globally topology
   information. Distance vector routing protocols such as RIP and BGP
   are used for reference. NP-MNRP protocol is consisted of network
   reachable information advertisement process and node potential
   calculation process.  But unlike those protocols, NP-MNRP ensures the
   following properties.

   (1) Multiple feasible next-hops for each destination. When node finds
   the main next-hop unreachable, it chooses one from the backup
   next-hops to forward the packet.

   (2) Accelerate the convergence speed and reduce route flap. Compared
   with the single shortest-path routing, NP-MNRP can effectively avoids
   congestion and shorten protection switching delay.  The path
   establishment and maintenance can be accomplished by routing
   information advertisement mechanism between peers. The control
   overhead of the protocol is smaller than other multi-path routing
   protocols. When kinds of concurrent failures occur in network, NP-
   MNRP can provide more feasible next-hops and high recovery
   probability.

2. Terminology

   Carrier Network: The network in which the nodes run Node Potential
   Oriented Routing Protocol.

   User Network: The network that needs message transfer service
   provided by Carrier Network.

   Boundary Node: According to the location of nodes in the carrier
   network, the nodes are divided into boundary nodes and intermediate
   nodes. Boundary nodes are also divided into two categories according
   to the flow direction. In terms of user network flow, the node
   through which flow into the carrier network, is called ingress node;
   the node through which flow out of the carrier network, is called
   egress node.



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   Intermediate Node: The other nodes in the carrier network except the
   Boundary Nodes.

   Potential Reference Node: The egress nodes which the user network
   traffic flows out from the carrier network. In the route calculation
   process, these nodes will be set its node potential value to zero and
   be act as reference node in node potential computation procedure.
   Network Layer Diagram: The diagram that describes the distribution of
   the layer value of every node relative to a destination node.

   Node Potential: A metric that measures the accessibility from a node
   to zero potential nodes in the carrier network.

   Router ID: A 32-bit number assigned to each router running the NP-
   MNRP protocol. This number uniquely identifies the router in the
   carrier network. One algorithm for Router ID assignment is to choose
   the largest or smallest IP address assigned to the router.

   Set of Available Next-hops: The set of available next-hops of node i
   when it sends packets to the destination node j, which is denoted as
   A(i,j).

   Network Layer Reachable Information Flood Advertisement Packet
   (NLRI-FAP): The packet is used to advertise the information of
   binding relations between network prefix and egress nodes to its
   neighbors. IP address and subnet mask of its binding user network are
   included in this packet.

   Network Layer Reachable Information Specific Request Packet (NLRI-
   SRP): The packet is used to request a particular egress node for
   certain prefix binding relationship information. IP address and
   subnet mask of user network whose binding relationship needs to know
   are included in this packet.

   Network Layer Reachable Information Direction Answer Packet (NLRI-
   DAP): The packet is used to respond to a Network Layer Reachable
   Information Specific Request Packet. IP address and subnet mask of
   user network and its bound router ID are included in this packet.

   Network Layer Graph Construction Trigger Packet (NLG-CTP): The packet
   is used to trigger the building of network layer diagram.

   Network Layer Graph Information Advertisement Packet (NLG-IAP): The
   packet is used to advertise its layer information relative to one
   egress node to its neighbors. The egress node ID and its layer value
   relative to this egress node is included in this packet.

   Network Layer Graph Routing Request Packet (NLG-RRP): The packet is



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   used to request the neighbors to update it's layer information
   relative to one egress node and this egress node ID is included in
   this packet.

   Network Layer Graph Request Update Packet (NLG-RUP): The packet is
   used to inform the nodes which are on a particular layer relative to
   one destination node, to rebuild their layer information and that
   layer value is included in this packet.

   Link State Detect Packet (Detect): The packet is used to detect the
   link status between itself and its neighbors. The sequence number of
   this packet and the period for sending Detect are included in this
   packet.

   REPLY Packet (REPLY): The packet is used to respond to the Detect
   indicating the good link state. The sequence number of this packet
   and the period for sending Detect are included in this packet.

3. Protocol operation

3.1. LFBs Network prefix information advertisement

   Because NP-MNRP protocol is designed as an IGP inside the autonomous
   system, it should route transit network traffic and local network
   traffic. The network IP prefix is divided into two parts: the IP
   prefix information of transit network and the IP prefix information
   of the network running NP-MNRP protocol own.

   In view of NP-MNRP protocol, network is divided into user network and
   carrier network, as shown in the figure 1. User network is
   abbreviated as UN and carrier network is abbreviated as CN. Each node
   in CN will run NP-MNRP protocol to establish multiple next-hops
   routing information base. Otherwise, it is not necessary for nodes in
   UN to run NP-MNRP protocol.

   CNRT: Carrier Network Router
          ----                ----                ----
         /    \              /    \              /    \
        *  UN1 *            *  UN2 *            *  UN3 *
         \----/              \----/              \----/
           |                   |                   |
     ******|*******************|*******************|******
     *  +-----+             +-----+             +-----+  *
     *  |CNRT1|-------------|CNRT2|-------------|CNRT3|  *
     *  +-----+             +-----+             +-----+  *
     *     |                   |                   |     *
     *     |                   |                   |     *
     *  +-----+             +-----+             +-----+  *



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     *  |CNRT5|-------------|CNRT6|-------------|CNRT4|  *
     *  +-----+    CN       +-----+             +-----+  *
     ******|***************************************|******
         __|_                                    __|_
        /----\                                  /----\
       *  UN5 *                                *  UN4 *
        \----/                                  \----/
                        Figure 1: Network Model

   The nodes in UN will finish local communication and transmit the
   network traffic whose destinations are not in the user network itself
   to the Carrier network. The network prefix of UN is named as Network
   Layer reachable information. Carrier network mainly transfer transit
   traffic for UN. The network prefix of CN is treated as network
   topology information and will be advertised by potential calculation
   process. The boundary nodes of CN are also named as egress nodes.
   They advertise network layer reachable information to neighbor nodes
   periodically and initiate node potential calculation procedure for
   itself.

   This advertisement method separates the information of CN topology
   from the network layer reachable information and advertises them in
   different manner. The advertisement of topology information is
   independent with network layer reachable information. From this way,
   the flexibility of routing information distribution can be enhanced.

   3.1.2 Network layer reachable information advertisement

   Network layer reachable information that means the user network
   prefix is advertised through NLRI-FAP, NLRI-SRP and NLRI-DAP packets.
   The boundary nodes in CN are responsible for advertising user network
   reachable information, as shown in the figure 2.

            ................
            .  UN          .
            . Host1  Host2 .
            .    \    /    .
            .     \  /     .
            .   +-----+    .
            .   |UNRT1|    .
            .   +-----+    .    Host1  Host2           .Host1  Host2
            .......|........        \   /                   \   /
   ****************|*****************\ /*****************    \ /
   *           +------+            +------+              * +-----+
   *     +-----|CNBRT1|------------|CNBRT2|----------------|UNRT2|
   *     |     +------+            +------+              * +-----+
   *     |         |                   |                        |
   *     |         |                   |                 *      |



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   *     |      +-----+             +-----+       +-----+*      |
   *     |      |CNRT6|-------------|CNRT3|-------|CNRT2|*      |
   *     |      +-----+             +-----+       +-----+*      |
   *     |         |                   |             |   *      |
   *     |         |                   |             |   *      |
   * +------+   +-----+             +-----+      +------+*      |
   * |CNBRT4|---|CNRT5|-------------|CNRT4|------|CNBRT3|-------+
   * +------+   +-----+     CN      +-----+      +------+*
   ******|******************************************/ \***
   ......|.........                                /   \
      +-----+     .                             Host1  Host2
      |UNRT3|     .
      +-----+     .
        / \       .
       /   \      .
   Host1  Host2     .
   ................
      Figure 2: Network layer reachable information advertisements

   CNRT: Carrier Network Router.

   CNBRT: Carrier Network Boundary Router.

   The boundary nodes in CN advertise network layer reachable
   information to neighbor nodes periodically through NLRI-FAP.  Once
   receiving the NLRI-FAP, the nodes in CN extract network prefix
   information from packets and add them to the network layer reachable
   information database of their own.

   When the nodes in CN don't know user network prefix, these nodes will
   act as inquirers and send NLRI-SRP to query other nodes and set a
   query timer. When a node receives the NLRI-SRP, and the network
   prefix information or attached router information is in its database,
   it responses to inquirer with a NLRI-DAP packet. Otherwise, it sends
   the NLRI-SRP packet to its neighbors except for the enquirers. This
   process will continue until the inquirer get an response from other
   nodes or such query timer is timed out.

   When bound to the egress node (relative information is absent in
   network layer reachable information database of the node), the node
   send NLRI-SRP flooding to inquirer, called enquirers.

3.2. Neighbor Node Discovery and Adjacency establishment

   When a new node joins in the network, other nodes discover it and
   initialize their local routing tables as the following steps.

   (1) Broadcast a Detect packet and a NLG-CTP packet. This node sets



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   the sequence number of Detect with 0.The Detect will be sent
   periodically by defaulted period set in the protocol;

   (2) When other nodes receive a Detect packet or a NLG-CTP packet,
   they operate as follows.
       (a) If the received Detect message is ca from an unknown node and
       sequence number is  equal to 0, the receivers know that a new
       node add to network and add it to their neighbor node database
       and record sequence number of  the Detect message;
       (b) Reply to the unknown node with an REPLY packet; Send a NLG-
       IAP packet which contains all egress nodes information in the
       database;
       (c) According to the computation rules of node potential, they
       compute layer value and potential value relative to the egress
       node.
   (3) When received a REPLY packet and a NLG-IAP packet, the new node
   operates as follows.
       (a) Adds the neighbor node to routing information database;
       (b) According to NLG-IAP, it calculates its own layer value as
       following formula.
          L(i,i)=0,
          L(i,j)=min[L(k,j)]+1,
          for each k blongs to Ki, j blongs to N, and k,j are not equal
       to i.
          L(i,j) is the layer value of node i reference to egress node
       j, N is the set of network nodes, Ki is the set of neighbor nodes
       about node i.
       (c) Based on the layer values of its neighbors, bandwidth and its
       own layer value, the new node computes node potential value of
       its neighbors and its own.

3.3. Calculation of node potential value
   3.3.1 Definition of node potential value

   NP-MNRP defines node potential value as a mixed metric of hop count
   and bandwidth. Hop count metric records the number of routers which a
   packet passes through and each router is recorded as one hop. The
   actual link bandwidth is allocated\configured by router in the
   network initialization.

   3.3.2 Protocol packets sending and processing

   3.3.2.1 Network Layer Graph Routing Request Packet processing

   Network Layer Graph Routing Request Packet (NLG-RRP) has two
   different types. One type is all nodes layer information request
   packet which will request the receiver to send layer information of
   all nodes. The other is partial nodes layer information request



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   packet which will request the receiver to send layer information of
   the specified nodes.

   The NLG-RRP will be used in the following conditions.

   Condition 1: When a new node is attached to the network, all nodes
   layer information request packet will be sent to its neighbors.

   Condition 2: When the node want to get some certain network prefix
   information from its neighbors, partial nodes layer information
   request packet will be sent.

   Once receiving a NLG-RRP packet, each node should process as the
   following steps.

   (a) Firstly, the type of the packet will be verified whether or not
   it is a correct NLG-RRP packet.

   (b) When NLG-RRP is the all nodes layer information request packets,
   it sends its own layer information relative to the other nodes to the
   request node.

   (c) When NLG-RRP is the partial nodes layer information request
   packet, it sends its own layer information relative to the
   destination node in the packet to the query node.

   3.3.2.2 Network Layer Graph Information Advertisement Packet sending

   Network Layer Graph Information Advertisement Packet (NLG-IAP) is
   broadcast to its neighbors in the following cases.

   Case 1: Each layer value of every node is specified after the network
   layer graph has been divided.

   Case 2: When the layer information of any node is changed, which may
   be caused by the change of layer values of some routers when they
   received NLG-FAP or some new nodes are added to the network.

   Case 3: A NLG-RRP packet is received and the layer value of receiver
   reference to certain egress node is changed.

   The processing rules of NLG-IAP are described in section 3.5.

   3.3.3 Calculation of the node potential value

   In NP-MNRP, the node potential value is a mixed metric, including hop
   count and actual link bandwidth. Each egress node activates its
   neighbors to build Network Layer graph by sending a NLG-CTP packet to



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   neighbors. Calculated as follows.

   (1) In the algorithm initialization, egress node assigns its layer
   value as 0, and then sends a NLG-CTP packet to its neighbors, which
   contains the actual link bandwidth.

   (2) The neighbor node that received a NLG-CTP packet from the 0-
   layer node sets itself as 1-layer, and generates a NLG-CTP packet and
   sends to its neighbors. And so on.

   (3) Repeat the above step (2) until the nodes whose layer value are
   smaller than f-layer which have been determined.

   (4) After the f-layer has been constructed completely, each node in
   f-layer knows that it is in f-layer and knows that which neighbors
   are in f-1 layer. The nodes in f-1layer know that which ones are in f
   layer, which ones are in f-1 layer, and which ones are in f-2 layer.

   (5) Supposed f-layer has been constructed, and the algorithm has not
   been terminated, then the construction of the f +1 layer will begins.
   The nodes in f-layer will send a NLG-CTP packet to its neighbors.

   (6) When all the nodes are traveled, algorithm ends.

   All nodes in the network not only are aware of their own layer value
   but also know the layer values of their neighbors and the actual
   bandwidth between themselves.

   Next, each node calculates the potential value as follows.

   (1) 0-layer nodes directly define their own potential value as 0;

   (2) Each node of the other layers chooses the largest potential value
   node among its neighbors in the same and lower layers as its
   reference node for defining potential value, then defines its
   potential value as potential value of the reference node plus one and
   potential values of its neighbors which are equal to their layer
   value;

   (3) When each potential value of the neighbors is defined, the node
   will choose the neighbor nodes whose potential values are less than
   its own as feasible next-hops of itself.

3.4. network event sensing

   NP-MNRP protocol can sense events such as new node add to network or
   neighbor node is down. The node senses these events through sending
   out Detect packet and receiving REPLY packet periodically.



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   3.4.1 Message sending and processing

   Each NP-MNRP node broadcasts periodically Detect packet. When a
   Detect packet is received, the receiver sends a REPLY packet to the
   sender.  The detailed steps are as follows.

   Step1: Each node broadcasts periodically a Detect packet. Detect
   packet carries a sequence number and  periodic interval.

   Step2: When a Detect packet is received, its sequence number is
   compared with the expected sequence number for this neighbor. Then
   the receiver sends a REPLY packet to the sender and evaluates inverse
   link quality according to the sequence number.

   Step3: When a Reply packet is received, its sequence number should be
   equaled to the sequence number of the Detect packet.  Then the
   receiver evaluates link quality according to the sequence number and
   the use of sent/receive message time.

   3.4.2 Forward direction link sensing

   A(Ti) represents the mean interval from node i sending out Detect
   packet to receiving REPLY packet. FA (Ti) represents the latest mean
   interval time. Node i adjust the period of sending out Detect packet
   according to the following rules.

   (1) If FA(Ti) < A(Ti), it means that the link quality is stable. At
   this period, when three continuous Detect packets are all low, then
   increase the Detect interval;

   (2) If FA(Ti) > A(Ti), it means that the link quality is unsteady or
   become bad. At this period, when three continuous Detect packets are
   all high, then reduce Detect interval;

   (3) When a Detect packet is sent out but a REPLY packet is not
   received in the 2*FA(Ti) time, the node will reduce the period at
   half, then continue sending out the next sequence number Detect
   packet. If a REPLY packet still not received, the node insulates that
   node and thinks link breakdown or link congestion.

   (4) The isolate node will not be used as the next-hop to forwarding
   packets. The processing node should continue sending Detect packet
   and adjust strategy according to the following conditions.
       (a) If three continuous REPLY packets received, then the node
       deletes the isolate node and uses nodes which reply the REPLY
       packet as the next-hops to forwarding packets.

       (b) If no packet is received after 6 Detect intervals, so that



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       node is thought to be breakdown, unable to send Detect packet
       again. Waiting

       (c) If the node can receive a Detect packet or a REPLY packet
       which is send out from isolate node, and then it will continue
       sending a Detect packet until the isolate node recovery or judge
       node breakdown.
   3.4.3 Inverse link sensing

   Each node broadcasts periodically Detect packet. Every Detect carries
   a sequence number and the interval.

   When a Detect packet is received, compared sequence number with the
   next expected sequence number for this neighbor, if the sequence
   number of the received Detect packet is higher than the expected,
   then one or more Detect packets have been missed. If the sequence
   number is lower, then this neighbor decrease the Detect interval, and
   part of the history must be undone.

   From the history of received Detect packets, a node computes an
   estimate of the inverse link quality.

3.5. Update of the node potential

   3.5.1. Update of network layer value

   As the set of next-hop is empty, the node will trigger update about
   the layer value through the following operations.

   (1) Firstly, the node will check whether the set of its neighbors on
   the same layer is empty. If is not, it will change itself layer value
   and generate NLG-IAP packets that are sent to its neighbors.

   (2) If the set is empty, then the node will perform the following
   steps.

       (a) Flooding NLG-RUP packets, whose layer value will be revised
       to the old layer value minus 2, however, if old layer value minus
       2 is less than 0, the value is set to 0. What's more, all
       information about this egress node will be deleted.

       (b) The node received a NLG-RUP packet will check if it has ever
       received this message. If having received such message, the
       packet will be ignored, otherwise view the layer value in this
       packet. If the value is greater than the value of its own, the
       node will discard the packet, otherwise, go on flooding NLG-RUP
       packets to its neighbors and delete all information about this
       egress node.



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       (c) If the layer value in the packet is equal to its own, the
       node will stop flooding to send NLG-RUP and send a NLG-CTP packet
       about the egress node.

       (d) Neighbor node received a NLG-CTP packet will calculate its
       new layer value. If new value is same with the original, the node
       stops sending NLG-CTP packets and the layer value update
       algorithm will terminate.

   3.5.2. Update of node potential value The potential value of the
   nodes will be updated in the following conditions.

   (1) Potential value update caused by NLG-IAP packet. The main content
   of a NLG-IAP packet are layer information of a node relative to the
   egress node in the network. The node adjusts its potential value
   according to the NLG-IAP packets received from its neighbors.
   Specific updated as follows.

       (a) NLG-IAP packet generation When the node finds its layer
       information relative to one certain egress node changed, the new
       layer information relative to all egress nodes will be written
       into its generated NLG-IAP packet.

       (b) NLG-IAP to send The node will broadcast its generated NLG-IAP
       packets to its neighbors, and then wait for confirmation from its
       neighbors. When the node receives REPLY pockets with sequence
       number 0XFFFF from its neighbors, this update ends.

       (c) When the node received the NLG-IAP packet, it performs the
       following steps.

       Firstly, this node will verify NLG-IAP packet. If the packet is
       validated, it sends a REPLY packet with sequence number 0XFFFF to
       source node of NLG-IAP packet.

       Secondly, this node will extract layer information from the NLG-
       IAP packet supposing a received routing entries includes RUIi =<
       RouterID, EgressnodeID, Layi> and the corresponding routing entry
       stored in the database is RUI'i =< RouterID, EgressnodeID,
       Lay'i>, when one of the following three cases are met, the node
       update its own routing table according to the information
       received.

       Case 1: If the EgressnodeID included in the received routing
       table entry dose not exist in its own routing table, the router
       will add it and send a NLG-RRP packet about the destination
       address of the network to its neighbors. After received NLG-IAP
       packets, it will calculate its layer value relative to this



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       egress node according to formula in 3.2, and get layer values of
       it's neighbors, then define the potential value of neighbor node
       reference to this destination node.

       Case 2: If the EgressnodeID included in the received routing
       table entry exists in its own routing table and Lay'i < Layi, the
       router will adjust the layer values of its neighbors and
       potential value. If the potential value of neighbor is greater
       than its own and the neighbor node is just in its own next-hop
       collection, the router will remove the node from next-hop
       collection, if not, do nothing.

       Case 3: If Layi < Lay, then the router will adjust the layer
       value of neighbor node and potential value. If the potential
       value of neighbor is less than its own and the neighbor node is
       not in its own next-hop collection, then the router will add it
       into the next-hop

   (2) Potential value update caused by the change of layer value

   When the layer value reference to a particular destination node
   changes, firstly it will modify layer value of itself and its
   neighbors. Then the new potential value will be calculated according
   to update strategy.

4. Routing information base

   Each routing node maintains the Routing Information Base to forward
   IP packets. NP-MNRP protocol can calculate multiple next-hops routing
   information in the network. The route computation process descried in
   Section 3 will record all the feasible next-hops for every
   destination. The multiple next-hops routing entry is composed of
   three fields.

   The first field is named as destination IP address field.

   The second field is named as the destination IP address mask filed.
   The first and second fields are 32-bit numbers which define network
   destination information of each routing entry. And the route
   information base is indexed by the first and second field.

   The third field is named as feasible next-hop filed, whose form is a
   couple of next-hop IP address value and node potential difference
   value. The next-hop IP address is IP address of the neighbor node who
   will act as a feasible next-hop for this routing node to forward IP
   packets to the network destination. Compared with the single next-hop
   routing information, the number of feasible next-hop filed in a
   multiple next-hops routing entry may be a value bigger than one.



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   The routing node will gain more agility in IP packet forwarding
   procedure. It can choose forward all the packets to one best next-hop
   and use other feasible next-hop entries as backup entries. Through
   this way, the network availability will be improved in the scene that
   network failure or mal-function occurs frequently. It can also choose
   forward all the IP packets to all feasible next-hop entries. In this
   manner, this routing node can assign each next-hop a traffic ratio
   for each destination. All the packets will be forwarded to variable
   next-hop pro rata. This will make the network resource utilization
   more evenness and avoid network congestion in some ways.

5. NP-MNRP packets format

   The NP-MNRP protocol runs directly over the IP network layer. Before
   any packet format is described, the details of the NP-MNRP
   encapsulation are explained.
5.1. Encapsulation of NP-MNRP packets

   NP-MNRP runs directly over the Internet Protocol's network layer.
   Therefore, NP-MNRP packets are encapsulated solely by IP and local
   data-link headers. NP-MNRP does not define a way to fragment its
   protocol packets, and depends on IP fragmentation when transmitting
   packets larger than the network MTU.

   NP-MNRP uses IP protocol number 99. Routing protocol packets are sent
   with IP precedence set to inter-network Control. NP-MNRP protocol
   packets should be given precedence over regular IP data traffic, in
   both sending and receiving.

5.2. Packet format

   There are nine distinct NP-MNRP packet types. All NP-MNRP packet
   types begin with a standard 20 byte header. This header is described
   first. Each packet type is then described in a succeeding section. In
   these sections each packet's division into fields is displayed, and
   then the field definitions are enumerated.

   5.2.1 The NP-MNRP packet header

   Every NP-MNRP packet starts with a standard 20 byte header. This
   header contains all the information necessary to determine whether
   the packet should be accepted for further processing. This
   determination is described in Section 5.2 of the specification.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version #    |     Type      |        Packet length        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Router ID                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Check Sum           |      Authentication Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 4-7)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version
   The NP-MNRP version number. This specification documents version 1
   of the protocol.

   Type
                               Type   Description
                              ---------------------
                               1      NLRI-FAP
                               2      NLRI-SRP
                               3      NLRI-DAP
                               4      NLG-CTP
                               5      NLG-IAP
                               6      NLG-RRP
                               7      NLG-RUP
                               8      Detect
                               9      REPLY

   Router ID
   The Router ID of the packet's source.

   Check Sum
   The standard IP checksum of the entire content of the packet. Note
   that the packet starts with the NP-MNRP header but excluding the 64-
   bit authentication field. If the length of the package is less than
   16-bit, 0 byte WOULD be added before the checksum byte.

   Authentication Type Identify the authentication procedure used for
   the packet. Authentication is discussed in the specification.

   Authentication Info 64-bit authentication information field depends
   on the chosen authentication type, to carry identification
   information such as identity authentication.

   5.2.2 Various types of protocol packets

   NP-MNRP protocol packets have total of 9 species.



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   5.2.2.1 Network Layer Reachable Information Flood Advertisement
   Packet, NLRI-FAP

   NLRI-FAP packet is NP-MNRP packet type 1.The packet is send by an
   egress node in the carrier network and is used to advertise the user
   network prefix information which is bound to this node. The node that
   received this packet WOULD consider this egress node is reachable and
   the user network which is bound to this node is reachable too.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version #   |     1        |        Packet length          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Router ID                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Check Sum           |      Authentication Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 4-7)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 IP address of the network 1                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Subnet mask of the network 1                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              ......                                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                IP address of the network n                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Subnet mask of the network n                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   IP address of the network
   The IP address of a user network is bound to this egress node.

   Subnet mask of the network
   Subnet mask of user network is denoted in the above field.

   5.2.2.2 Network Layer Reachable Information Specific Request Packet,
   NLRI-SRP

   NLRI-SRP packet is NP-MNRP packet type 2.This packet is used by the
   node in the carrier network to request the network layer reachable
   information. When the node doses not know which egress node, one
   network prefix is bound to, the NLRI-SRP packet is sent.



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   If the IP address and the subnet mask of the network 1 is all 0, all
   the network prefixes WOULD be requested, and usually this request is
   sent by a node which just joins into the carrier network.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version #   |     2        |        Packet length          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Router ID                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Check Sum           |      Authentication Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 4-7)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               IP address of the network 1                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Subnet mask of the network 1                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              ......                                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               IP address of the network n                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Subnet mask of the network n                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   IP address of the network
   The IP address of a user network whose binding relationship this
   node want to request.

   Subnet mask of the network
   The Subnet mask of a user network denoted in the above field, who
   binding relationship this node wants to request

   5.2.2.3 Network Layer Reachable Information Direction Answer Packet,
   NLRI-DAP

   NLRI-DAP packet is NP-MNRP packet type 3. The node that receives the
   NLRI-SRP packet WOULD check its information database to seek for the
   corresponding binding relationship. If the binding relationship
   exists in its own information database, it WOULD send NLRI-DAP packet
   to the requesting node, if not, it WOULD send NLRI-SRP packets to its
   all neighbor nodes except for the requesting node.




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   If a node who sends the NLRI-SRP packets at the same time receives
   more than one packet about the same IP prefix binding relationship,
   and these packets are conflictive, it WOULD go on sending NLRI-SRP
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version #   |     3        |        Packet length          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Router ID                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Check Sum           |      Authentication Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 4-7)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 IP address of the network                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Subnet mask of the network 1                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Egress node ID 1                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              ......                                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              IP address of the network n                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Subnet mask of the network n                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Egress node ID n                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   IP address of the network
   The IP address of a user network whose binding relationship is wants
   to know in the receiving NLRI-SRP packet.

   Subnet mask of the network
   The subnet mask of a user network denoted in the above field, whose
   binding relationship is wants to know in the receiving NLRI-SRP
   packet.

   Egress node ID
   This field denotes the user network, whose IP address and subnet
   mask emerge in the front two fields, is bound to this egress node.

   5.2.2.4 Network Layer Graph Construction Trigger Packet, NLG-CTP




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   NLG-CTP packet is NP-MNRP packet type 4.When one egress node joins
   into the carrier network, it WOULD send this packet to urge the other
   nodes to build network layer graph relative to itself.

   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
    Version #   |     4        |        Packet length          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Router ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
           Check Sum           |      Authentication Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
               Authentication Info(8 array 4-7)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
                        Egress node ID                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
                        Layer value                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Egress node ID The node that received this packet calculates its
   layer value relative to this egress node.

   Layer value The value of the sender relative to the node denoted in
   the above field

   5.2.2.5 Network Layer Graph Information Advertisement Packet, NLG-IAP

   NLG-IAP packet is NP-MNRP packet type 5. This packet is sent to all
   neighbor nodes using multicast address to advertise its layer value
   relative to the node whose ID includes in this packet, this packet is
   usually to start the neighbor nodes to adjust their potential
   dynamically.

   0                   1                   2                 3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    |    5         |          packet length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Router ID                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Egress node ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   |           Check Sum           |      Authentication Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 4-7)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Egress node ID 1                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Layer value 1                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       .......                                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Egress node ID n                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Layer value n                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Egress node ID
   The receiver need adjust its layer value relative to this node

   Layer value
   This is the layer value of the sender relative to the egress node
   denoted in the above field.

   5.2.2.6 Network Layer Graph Routing Request Packet, NLG-RRP

   NLG-RRP packet is NP-MNRP packet type 6. This packet is used by one
   node to request the neighbor nodes to send their own layer
   information relative to the appointed egress node to it. This packet
   has two types: one is for all nodes and the other is for some nodes.
   If the egress node ID in the packet is empty, the packet is NLG-RRP
   packet for all nodes, if not; the packet is NLG-RRP packet for the
   appointed nodes included in this packet.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    |    6          |          packet length        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Router ID                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Check Sum           |       Authentication Type     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 4-7)                |



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Egress node ID1                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Egress node ID2                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       .......                                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Egress node ID
   This field denotes the receiver need to respond its layer value
   relative to this egress node.

   5.2.2.7 Network Layer Graph Request Update Packet, NLG-RUP

   NLG-RUP packet is NP-MNRP packet type 7. When a node finds its next
   hops and its neighbors on the same layer are all unreachable, it
   sends this packet to neighbors to update its layer value.
   0                   1                   2                     3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    |    7          |         packet length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Router ID                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Check Sum           |      Authentication Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 4-7)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Egress node ID                            |


   Egress node ID
   This field denotes the receiver needs to update its value relative
   to this node

   Layer value
   The layer value in NLG-RUP packet is the layer value relative to
   high egress node minus 2.

   5.2.2.8 Link State Detect Packet, Detect

   Detect packet is NP-MNRP packet type 8. This packet is periodically
   sent to neighbor nodes to evaluate the link quality.




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   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    |    8          |         packet length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Router ID                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Check Sum           |      Authentication Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 4-7)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Sequence number           |         Period                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Sequence number
   The sequence number in this packet is the sequence number of the
   Detect message, and it is an increasing positive integer.

   Period
   The period in this packet is the interval time between this to the
   last one.

   5.2.2.9 REPLY Message Packet, REPLY

   REPLY packet is NP-MNRP packet type 9. The node that received a
   detect packet will send a reply packet to the sender, which can
   evaluate the reverse link quality according to this packet. The
   sequence number in this packet denotes it is the reply to the Detect
   message that has the corresponding sequence number. If the number is
   full-1, it means the packet is confirmation message to a NLG-IAP
   message.


   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Byte 1     |    Byte 2     |   Byte 3      |   Byte 4      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    |    9          |    packet length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Router ID                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Check Sum           |      Authentication Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   |               Authentication Info(8 array 0-3)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Authentication Info(8 array 4-7)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Serial number             |         Period                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Serial number
   The sequence number in this packet is the sequence number of the
   REPLY, and it is an increasing positive integer.

   Period
   This field denotes that the node sending this packet will sends
   Detect message at this period.
6. Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997.



7. Author's Address

   Julong Lan
   National Digital Switching System Engineering and Technological
   Research Center
   NDSC, No.7 , Jianxue Street,Jinshui District
   Zhengzhou, 450002,
   P.R.China
   Phone: +86-371-8163-2988
   Email: ndscljl@163.com
   URI:   http://www.ndsc.com.cn/

   Jianhui Zhang
   National Digital Switching System Engineering and Technological
   Research Center
   NDSC, No.7 , Jianxue Street,Jinshui District
   Zhengzhou, 450002,
   P.R.China
   Phone: +86-371-8163-2988
   Email: ndsc155@163.com
   URI:   http://www.ndsc.com.cn/

   Bin Wang
   National Digital Switching System Engineering and Technological
   Research Center
   NDSC, No.7 , Jianxue Street,Jinshui District
   Zhengzhou, 450002,



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   P.R.China
   Phone: +86-371-8163-2909
   Email: ndscmt@163.com
   URI:   http://www.ndsc.com.cn/

   Wenfen Liu
   National Digital Switching System Engineering and Technological
   Research Center
   NDSC, No.7 , Jianxue Street,Jinshui District
   Zhengzhou, 450002,
   P.R.China
   Phone: +86-371-8163-0340
   Email: wenfenliu@sina.com
   URI:   http://www.ndsc.com.cn/

   Youjun Bu
   National Digital Switching System Engineering and Technological
   Research Center
   NDSC, No.7 , Jianxue Street,Jinshui District
   Zhengzhou, 450002,
   P.R.China
   Phone: +86-371-8163-2670
   Email: buyoujun2009@hotmail.com
   URI: http://www.ndsc.com.cn/

   Xin Li
   BEIJING UNIVERSITY OF POSTS AND TELECOMMUNICATIONS
   No.10 Xi Tu Cheng Road Haidian District
   Beijing,100876
   P.R.China
   Phone: +8613581614576
   Email: cplalx@gmail.com
   URI: http://www.bupt.edu.cn/


















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