dynamic router configuration protocol (drcp)

8/20/2019 Dynamic Router Configuration Protocol (DRCP)

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International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN 2278 – 0882

Volume 3, Issue 2, May 2014

Dynamic Router Configuration Protocol (DRCP)

Arif Tanvir

Lecturer, Department of CSE, Asian University of Bangladesh (AUB), Dhaka, Bangladesh

AbstractDynamic behavior of the network is all what we want

because that reduces our headache of managing thenetwork and we would rather expect the network tomanage itself. Here in this paper, I am daring to proposethe idea of DRCP along with the concept of GeneralizedRouter Discovery Protocol (GRDP) and Auto Subnetting

to automate the whole process of IP Allocation amongthe current routers in the world as well as the ones in thequeue to join the network. Five Regional Internet

Registries APNIC, ARIN, RIPE NCC, LACNIC and

AFRINIC will each be associated with five Master ZoneRouters which will be in charge of allocating IPs to therouters as they enter into the network. This may sound alittle dreamy at the moment, but you know, someone has

to dream. Why can’t that be me? I will try to explain allthe concepts and ideas as clearly as possible in this

paper.

Keywords - Dynamic Router Configuration, Router Discovery Protocol, Automatic IP Allocation, AutoSubnetting, Regional Internet Registries, Dynamic HostConfiguration Protocol, Cisco Discovery Protocol,

OSPF Routing Protocol, Backbone Area Border Router(BABR), Master Area Border Router (MABR), Sub Area Border Router (SABR).

1. Introduction

The concept of DHCP has been used as the backbone fordesigning the working mechanism of DRCP. Exchangeof messages between Master Zone Routers (MZR) andthe Client Routers (CR) of that zone controlled by it -has also been influenced by the messages exchanged

between DHCP Server & DHCP Client. The concept of

Cisco Neighbor Discovery Protocol has been used, aswell as extended to the level which allows detection ofdevices at Layer 3 instead of just Layer 2, with the useof GRE Tunnel and enabling GRDP on the tunnel

interface. Obviously allocation of IP to the router willinvolve subnetting and we will leave that to auto

subnetting algorithm which will deal with the IP Blocks

available at each zone and breaking that down to thelevel as requested by the routers.

2. IP & Subnet Configuration

DRCP supports 2 Mechanisms for Allocating IP address

Manual Allocation: Network Administrator of the

MZRs manually assigns one or more IP Addresses toRouter(s) of that Zone along with appropriate SubnetMask considering the direct request of IP Requirements

from the Client.Dynamic Allocation: DRCP assigns Permanent IP

Address(es) along with Subnet Mask with the use ofAuto Subnetting Algorithm to a Client considering the

Number of IPs requested by the client.

3. Related Terms

GRDP: General Router Discovery ProtocolDRCP MZR: It assigns IP addresses and other network

configuration parameters to the DRCP CRsDRCP CR: It obtains an IP address and other network

configuration parameters from a DRCP MZR.DRCP BABR: Backbone Area Border Router.DRCP MABR: Master Area Border Router.

DRCP SABR: Sub Area Border Router.

4. Dynamic IP Allocation Process

A DRCP CR obtains a valid IP address from a DRCPMZR in Three Steps:Discovering: The CR locates a MZR.Offering: The MZR offers configuration parameters

such as IP Address & Subnet Mask to the CR.

Acknowledging: CR confirms the offered configuration


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Fig.1 Dynamic IP Allocation Process

Fig.1 illustrates the dynamic IP address allocation stepswhich are described as follows:

Discovering:

The DRCP CR broadcasts a DRCP-DISCOVERmessage to locate a DRCP MZR. The DRCP MZR forthat Zone sends reply to the CR upon receiving theDRCP-DISCOVER message.

Offering:

A DRCP MZR that receives the DRCP-DISCOVERmessage offers an appropriate IP address & Subnet Maskto the CR in a DRCP-OFFER message.

When assigning an IP address & Subnet Mask to a CR,the MZR needs to confirm that the IP address to be

assigned is not used by any other device by sendingICMP Echo Request (ping) packets. If the server doesnot get any response within a specified period, it will

ping the IP address once again until a specified numberof ping packets are sent. If still no response is received,

the server will assign the IP address to the requestingCR; otherwise, the IP address will be marked as aconflicting IP address, and the MZR will choose anotherIP address.

Acknowledging:

The DRCP CR returns a DRCP-ACK message to DRCPMZR, confirming that it is starting to use the allocated

IP address.

5. Releasing an IP Address

When a DRCP CR no more need to use its IP addressanymore, it sends a DRCP-RELEASE message to notify

the DRCP MZR to release the IP address. That address

will be added to the Address Pool of the MZR of that particular zone.

6. General Router Discovery Protoco

(GRDP)

GRDP is a generalized version of CDP where the routersare not meant to be vendor specific and it runs on allmedia that supports Subnetwork Access Protoco(SNAP).

Use of SNMP (Simple Network Management

Protocol) with GRDP MIB (Management InformationDatabase) allows network management applications tolearn - Device type & SNMP Agent Address ofneighboring devices and to send SNMP queries to thosedevices.

But unlike CDP (Cisco Discovery Protocol) whichruns over Data Link Layer only, GRDP can run over

Network Layer as well. Therefore, two systems thasupport different network-layer protocols can learn about

each other. As with CDP each device configured sends periodic messages (Known as Advertisements) to amulticast address. In case of GRDP this period should be

much longer to reduce the network traffic. And therouter that is supposed to go offline must react instantly

rather than waiting for the timer for the advertisement toexpire. But there must be different periodic calculationfor Zonal Routers.

Each device advertises at least one address - Awhich it can receive SNMP messages. TheAdvertisements also contain time-to-live (holdtime)which indicates the length of time a receiving deviceshould hold GRDP information before discarding it

Each device also listens to the periodic GRDP messagessent by other devices in that particular zone in order tolearn about neighboring devices and determine whentheir interfaces to the media go up or down.

Here we are borrowing the concept of GRE (Generic

Routing Encapsulation) Tunneling protocol developed by Cisco that can encapsulate a wide variety of protoco packet types inside IP Tunnels, creating a virtual point-to-point link to Routers at remote points over an IPinternetwork.

Normally CDP requires a layer 2 connection toestablish the neighbor adjacency. But there are some

tricks to do that across a WAN using a GRE tunnel andenabling CDP on the tunnel interface. But generally aWAN link breaks a CDP neighbor chain.


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Let us now look at different Type Length Values(TLVs) which are blocks of information embedded in

GRDP advertisements

Table 1: Different Type Length Values (TLVs)

TLV Definition

Device-IDTLV

Identifies the device name in the formof a character string

AddressTLV

Contains a list of network addresses of both receiving & transmitting devices

Port-IDTLV

Identifies the port number on which theGRDP packet is sent

CapabilitiesTLV

Describes the device’s functionalcapability in the form of a device type

(A switch)

Platform

TLV

Describes the hardware platform name

of the device (Cisco 7500)

IP NetworkPrefix TLV

Contains a list of network prefixes towhich the sending device can forwardIP packets. This information is in the

form of the interface protocol and portnumber (Eth 1/0)

Full/halfDuplex TLV

Indicates status (duplex configuration)of CDP broadcast interface. It is used

by network operators to diagnose

connectivity problems between adjacentnetwork elements

7. Preventing Address Conflicts

After the CR receives an assignment from the MZR, itsends an Address Resolution Protocol (ARP) request tothe address that it has been assigned. If a reply to the

ARP request is received, the CR has detected a conflictand sends a DRCP-Decline message to the MZR. TheCR is then assigned the next available address in thescope. A scope must be properly defined and activated

before CRs can use the DRCP for automatic TCP/IPconfiguration. A DRCP scope is an administrativecollection of IP addresses and TCP/IP configuration

parameters that are available for assignment to the CRs.

A scope has the following properties:- A scope name, assigned when it is created.- A range of possible IPs from which to include or

exclude addresses used in DRCP offers.- A unique subnet mask, which determines the

network ID for an IP address in the scope.

8. Auto Subnetting

The concept of auto-subnetting is essential here, becausewe are letting both Manual & Automatic allocation ofnetwork configuration to be a part of DRCP. And whenwe say Automatic Allocation it refers to allocation of IP

as well as Subnet Mask based on the requirements of theCRs.

What it does is when a request for assignmentcomes; at first it checks the class of the requested blockof IP Address as well as the number of available

unassigned IPs of that class. And then a subnet mask isset to release that IP from the general pool of IPs andassign to that specific CR.

But things to note here is the overlapping of IPamong different regions after the specification of subnet

mask. An improper masking may drag one IP from oneregion to another resulting in IP Allocation mishaps.

Sequence of Events:CHECK whether the requested IP is valid or not

CHECK whether the IP is from expected class or notFIND which of the 5 zones holds that IP

CHECK availability of the IP in that particular zoneFIND number of IPs neededFIND subnet mask to isolate those IPsAPPLY IP & Mask to the requesting CR

9. Blending the concept of DRCP with OSPF

As we know from OSPF routing protocol design thatamong the areas of OSPF one area needs to bedesignated as Backbone Area. I am actually proposing toextend this concept to one step further.

I would like to suggest that there should be FiveBackbone Areas associated with the three MZRs. For

example, the MZR associated with Backbone Area 1should have full control over the routers inside Area 1and so on. Each backbone area can have one or more

Backbone Area Border Router (BABR) associated withit as shown in Figure. 2. Actually I am proposing to add

an extra level to Area Hierarchy where there are threeBABRs spanned across five backbone areas creating anetwork of BABRs. Each Master Area Border Router

(MABR) of a particular BABR will eventuallycommunicate with the Sub Area Border Routers (SABR)


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Fig. 2 Proposed network of BABR, MABR & SABR

under its supervision. Here the function of the MABR isto maintain the Routing Table based on which zone it isin as well as which portion of which class of IP it issupposed to distribute to SABRs controlled by it. And

the function of the SABR would be to distribute IPs properly across the routers around the world as per need.I will leave the details for future work for time being.

10. Conclusion

This is mostly an imagination based on some real lifesystem of course. The whole idea was to automate the

entire process of IP assignment amongst the routers inthe world. I know it needs a lot of synchronization with

lot of things. But if we can look at things one at a time itmight make some sense in the near future where I

believe this whole imagination would not sound as weird

as it is now. We cannot just rule out human interactionwith the DRCP Protocol at all but what I am suggesting

here is to do so at the minimum level.

References

I am not including any reference from any research

paper or anything similar to that, because I have not usedany. I got the above mentioned ideas from the existingtechnologies as listed below:[1] DHCP (Dynamic Host Configuration Protocol)[2] CDP (Cisco Discovery Protocol)

[3] IP Subnetting Technique[4]

OSPF Routing Protocol

dynamic router configuration protocol (drcp)

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