Skip to main content

RTP, Reliable Transport Protocol of EIGRP

RTP is a Cisco proprietry protocol, used in EIGRP to manage the communication of messages between EIGRP-Speaking Routers.Reliable Transport or Delivery of EIGRP packets meansAcknowledgement is required from the receiving Router and the packet should be delivered in order. Ordered delivery is ensured by including two sequence numbers in the packet. One sequence Number is assigned by the sending router for the packet order Number and that is incremented by one each time the sending Router sends a packet. Another Number is the Last Acknowledgement number received from destination or Neighbor Router.Why ordered delivery of EIGRP Packets is important?

Let me give you a simplest example to explain question. Suppose an EIGRP Router’s Link went down and up after some time. But the neighbor Router receives a message of Link-up first and then Link-Down after! What will happen? Out of order execution of packets, can result in corruption of the Routing Database.
Guaranteed delivery is accomplished by a Cisco Proprietary process called Reliable Multicast which uses the reserved class D address 224.0.0.10. Each neighbor receiving a reliable multicast pakcet must unicast an acknowledgment. If EIGP does not get a reply from a neighbor it Unicasts to that Number for sixteen (16) times, if still the Router does not get Reply then that Neighbor router is decalared as dead.

Some types of EIGRP packets are also sent unreliably, means NO Acknowledgement and Ordered-delivery is required for those packets.

Let’s see types of EIGRP Packets and whether they are delivered Reliably or Un-Reliably.
Types of EIGRP Pakcets that are delivered Reliably
  • Updates convey route information. Unlike RIP and IGRP updates, these packets are transmitted only when necessary, contain only necessary information, and are sent only to routers that require the information. When updates are required by a specific router, they are unicast. When updates are required by multiple routers, such as upon a metric or topology change, they are multicast. Updates always use reliable delivery.
  • Queries and Replies are used by the DUAL finite state machine to manage its diffusing computations. Queries can be multicast or unicast, and replies are always unicast. Both queries and replies use reliable delivery.
Types of EIGRP Packets that are delivered Un-reliably
  • Hellos are used by the neighbor discovery and recovery process. Hello packets are multicast and use unreliable delivery.
  • Acknowledgments (ACKs) are Hello packets with no data in them. ACKs are always unicast and use unreliable delivery.
Labels:

Comments

Post a Comment

Popular posts from this blog

a file I/O error has occurred while accessing vmware converter

While converting physical Windows 7 machine to Virtual machine of infrastructure type, I got this error. The error seems it is unable to read/write source or destination datastore.

I have installed VMware-converter-en-6.2.0-8466193 on Windows 7 physical machine with option locally selected. (not at server/client option)

All of my ESXi servers are connected to the vCenter Server, so I had to use vCenter Server's IP address to send this physical machine to the virtual world.

The issue i found was with the dns resolution to the vCenter Server's hostname. Since I am not using the same dns server on the Windows 7 client machine. So I updated the host entries manually for the vCenter Server's hosname to it IP address.

After adding dns eteries to the hostfile of windows 7, I am not getting this "a file I/O error has occurred while accessing vmware converter" and the migration has started.
Post a Comment
Read more

Connection control operation failed for disk 'ide1:0'

I was getting this error while removing Operating System ISO image mounted on the Virtual Machine.

What worked for me, is
1. Uncheck the "Connected and Connect at power on" from Device Status.
2. Then Change the Device type from "Datastore ISO File to Client Device" Radio Button
3. and press OK to save the changes.

Note:- I was able to remove the mounted ISO only by directly logging to the ESXi at https://esxi-ip-address/ui

where it asks

"The guest operating system has locked the CD-ROM door and is probably using the CD-ROM, which can prevent the guest from recognizing media changes. If possible, eject the CD-ROM from inside the guest before disconnecting. Disconnect anyway and override the lock?"

You need to select yes to eject the CD-ROM and then remove the ISO file successfully.
Post a Comment
Read more

GNS3 Docker Error while creating node: Docker has returned an error: Cannot connect to host docker:80

Error while creating node: Docker has returned an error: Cannot connect to host docker:80 ssl:False [No such file or directory]

After adding docker template for Alpine Linux in gns3, you get above mentioned message when you want to use alpine linux in GNS3.

To get rid of this message you have to install Docker by following below link
curl -fsSL https://get.docker.com/ | sh

If you do not have curl installed then instal curl first with below command.apt-get install curl
After installing Docker you need to add your user name in the docker group with the following command. $ sudo usermod -aG docker your_username

Verify if the docker service is started with following command$ service docker status
If docker is not started then start with following command $ sudo service docker start
Logout from GNS3 Virtual Machines and log back. Start gns3 and use alpine linux.
Post a Comment
Read more