Tuesday, July 3, 2007

Routing protocols

Routing protocols
All routing protocols can be separated into two categories: Distance-Vector and Link- State. These two categories are defined by the algorithms that are used to calculate the best route.

Distance-vector routing protocols:
Uses metrics (hop counts) to determine the best route. Updates are broadcasted every 30 seconds. During this broadcast the router sends its routing table to the neighbor routers. To prevent routing loops, Distance-vector protocols are limited to 15 hops. If the destination network is more then 15 hops away (separated by more than 15 routers, the packet will be dropped) .

Link-state routing protocol
Uses the combination of metrics and bandwidth to determine the best route. In addition to routing table, the router builds and maintains a topology map of the network. Router use LSP (link state packets) broadcasts to send routing information to other routers. Updates are broadcasted every 2 hours. Link-state protocols can make more accurate routing decisions. Link-State protocols require more processing power and RAM than Distance-vector protocols.

Balanced Hybrid
is a combination of the Distance-vector and Link-State protocols. Balanced Hybrid routing protocols can calculate the best route more accurately than Distance-Vector with less overhead than Link-State protocol.
A Cisco router can be configured to use more than one routing protocol at the same time and can maintain routing tables for many different routing protocols simultaneously.

Distance-Vector protocols

RIP - Routing information protocol
RIP is a distance vector protocol. Suitable for small and medium size networks. Low overhead, simple to implement. The main limitation is 15 hops maximum (can't route through more than 15 routers). To start RIP on the router, type router rip from the router configuration mode, and then add network number that you want RIP to advertise. For example, Router(config-router)#network 122.122.0.0There are different version of RIP- RIP1, RIP2, and newer RIPng designed to be compatible with IPv6. Different versions of RIP are incompatible with each other. RIP version number is included in the RIP packet. RIP sends a copy of a routing table to other routers on the network every 30 seconds. The receiving router compares the routing table it receives from neighbor router with its own routing table, and if it detects changes, updates its routing table and sends updates to another neighbor router.When the router configured with RIP first starts up, it issues a request broadcast requesting the initial routing information from the neighbor routers.RIP is defined in RFC 1058 and RFC 1723.

IGRP - Interior Gateway Routing Protocol
IGRP is a Cisco's proprietary protocol initially introduced in 1988. Just like RIP, IGRP relies on broadcasts to update routing tables. There are many important differences between IGRP and RIP that make IGRP a much more advance routing protocol.Maximum hop counts is 255. In addition to hop count, IGRP uses Composite metrics: bandwidth, reliability, load, delay values to determine the best route. These values can be adjusted by the administrator. Updates are sent every 90 seconds to neighbor routers.Multipath routing - a data can be split end send over multiple links. This increases fault tolerance and provides more throughput.IGRP is suitable for large networks with complex topologies.To enable IGRP, type router igrp [autonomous system number]. For example, router igrp 100 will enable IGRP on the router and will assign the autonomous system number of 100. Then, from the router configuration prompt enter the network number that you want the router to advertise. For example: Router(router-config)#network 222.122.122.100
Link state protocols

OSPF - Open Shortest Path First
Link state protocol, developed by IETF for use on the Internet. OSPF is a very complex protocol with high overhead. Advantages of OSPF: More precise computation of the best route, ability to split network traffic between multiple paths, fast convergency.Link state routing tables are broadcasted only when the change (or link failure) is detected by a router.Support for Variable Length subnet masks. This means that unlike the RIP that only understands the major network numbers, OSPF can be used to route traffic between subnets.Support for broadcast networks (Ethernet, Token ring) and non-broadcast networks (ATM, x.25)OSPF protocol runs on top of IP protocol and consists of 3 subprotocols: Hello, Exchange, Flooding. Flooding protocol is used to transmit updates when change in topology is detected by a router responsible for the link. Database updates are transmitted in an encrypted form. OSPF messages can be secured by a password.OSPF routers exchange information with other OSPF routers within the same autonomous system, but can also be configured to send and receive updates from other autonomous systems.

EIGRP
Enhanced Interior Routing Protocol. Cisco's proprietary routing protocol, an improved version of IGRP. EIGRP uses "Distributed update algorithm" or "DUAL", it combines the Link-state and Distance-Vector algorithms. EIGRP is considered balanced hybrid protocol. Unlike IGRP that only understands major network numbers, EIGRP can be configured to use subnet masks and supernet masks. The format of the EIGRP routing table is different from IGRP routing table.Advantages of EIGRP are: Fast convergence, Support for multiple protocols, requires less bandwidth than Distance-vector protocols because only partial updates are broadcasted and only when changes in topology are detected. EIGRP does not use periodic broadcasts. Improved loop detection and prevention.

EGP
Exterior Gateway Protocol is a Distance-Vector protocol. EGP was designed to enable the exchange of routing information between different Autonomous Systems (AS) An AS is a set of routers and networks under the same administration. All parts of an AS must remain connected. Normally, routers in the AS only exchange routing information with other on the same AS. The purpose of the EGP is to exchange routing information and reachability information between Autonomous Systems.EGP has three procedures:Neighbor acquisition - determines whether 2 adjacent gateways agree to become neighbors. Neighbor Acquisition is a "two-way handshake" Becoming neighbors means that 2 Autonomous Systems agree to relay each other's traffic. An administrator defines the set of routers that can define a list of potential neighbors. The router will then accept a neighbor acquisition request only with members on the list. If a router receives a request from a router that has not been configured as a potential neighbor, it will reply with a Neighbor Acquisition Refusal. Neighbor Acquisition can also be refused if the router has ran out of memory and does not have enough space for extra routing table.Neighbor reachability - the procedure in which a router sends "hello" packets and another router suppose to reply with "I hear you" packets. Network administrator can configure the frequency of "hello" packets. The normal frequency is 30 seconds. One neighbor router can be configured to only send "hello" packets and another to only send "I hear you" packets. Also both routers can be configured to send both "hello" and "I hear you" packets.Network reachability - the procedure in which neighbor routers exchange the list of networks that can be reached through each neighbor. This information is used to update the routing tables in each of the Autonomous Systems. The EGP router polls its partner for a list of available networks.EGP was developed in 1982-1984, and is not capable of handling today's complex topologies. It is being replaced by the BGP. EGP cannot detect and prevent routing loops and heavily depends on the manual configuration by the administrator.

BGP - Border Gateway Protocol
Was designed to replace the EGP. The design started in 1989, and the most recent version is BGP-4. BGP uses "Path Vector" instead of "Distance Vector". Path Vector enable detection and prevention of loops in complex topology.BGP runs over TCP, and relies on TCP for error checking and resequensing packets.BGP-4 supports Classless Inter-Domain Routing (CIDR). Concept of CIDR is to have IP address and subnet mask independent of the IP address class. CIDR is the concept behind supernetting. In supernetting several class C addresses can be combined into one subnet. This solves the problem in which a medium size network needs more than one class C network (more than 254 hosts), but does not need class B address. By combining several adjacent class C addresses into one network address, only one additional entry has to be made in the routing table. Routing updates are sent only when change in topology is detected.BGP can be used to connect Autonomous Systems, to relay routing tables between Autonomous Systems , and can also be used for routing within Autonomous Systems.Running BGP requires a lot of manual configuration.
Potential problems with routing protocols.
Routing Loops
Routing loops occur when routing tables are not updated fast enough when one of the networks becomes unreachable. Due to the slow convergence (updates of routing table between all routers), some routers will end up with incorrect routing table and will broadcast that routing table to other routers. This incorrect routing tables will cause packets to travel repeatedly in circles.

Counting to infinity
Counting to infinity happens when packets end up in a routing loop. The hop count increases with every pass through a router on the network.
Solutions
Defining the maximum number of hops
When the number of hops reaches this predefined value, the distance is considered infinite and the network considered unreachable. This will not stop routing loops, but only limit the time that packet can travel inside the loop.
Split horizon
The packets can not be send back to the same interface that they originally came from. During the updates, one router does not send updates to the router that it received the information from.
Route poisoning
The router sets the cost of infinity for the unreachable network.
Split horizon with poisonous reverse
Combination of split horizon and route poisoning.
Triggered updates
The router sends updates of the routing table as soon as it detects changes in the network.
Hold-Downs
After the router detects unreachable network, the routers waits for a specified time before announcing that a network is unreachable. The router will also wait for a period of time before it updates its routing table after it detects that another router came online. Hold-downs can only partially prevent counting to infinity problem.

61 comments:

Anonymous said...

Genial post and this fill someone in on helped me alot in my college assignement. Thank you for your information.

Anonymous said...

I gοt this websіte fгοm my ρal who infοrmеd me
on the tορіc of thіs web pаgе and аt thе mοment this time I am browѕing this web
page and reading vеry informative content at this time.


Feel frеe to suгf to my blog ... using a bucket truck
Also see my page - altec bucket trucks for sale

Anonymous said...

Hi, every time i used to chеck ωeb site posts here
in the еаrly hours in the dаwn, because i enϳoy to
learn mοrе аnd more.


Also ѵisit my homepage: bucket trucks for sale online
Here is my web page ... bucket trucks for sale

Anonymous said...

If yоu are going foг best contents lіke myѕelf, sіmply pay a quick vіsit this
ωeb site ԁaily as it рrovides qualitу
contents, thanks

My weblοg; tens unit

Anonymous said...

Excellent site you have here but I was curious about
if you knew of any community forums that cover the same
topics talked about here? I'd really like to be a part of group where I can get responses from other knowledgeable individuals that share the same interest. If you have any suggestions, please let me know. Kudos!

My site best registry cleaner

Anonymous said...

Superb website you have here but I was curious about if you knew of any user discussion forums that cover the same topics talked about in this article?

I'd really like to be a part of community where I can get advice from other experienced people that share the same interest. If you have any recommendations, please let me know. Appreciate it!

My web site :: Http://www.Vub.ac.be

Anonymous said...

This medicine has to be taken for about half hour before taking part in sexual intimacy
as it will take time to point results. There are many categories to decide on from.
I'll probably never get accustomed to chatting, in my work room, with someone twelve thousand miles away in Indonesia.

My homepage: Porn Stream Flashx

Anonymous said...

With video chat, members can now confirm at least the visual identity of the person they are communicating with.

David Kamau is writes articles and dating service reviews at his site and blog.

This will save you the disappointment if she does not
offer what you were hoping she would.

Here is my webpage; nude sex chat

Anonymous said...

In addition for this, metabolism accelerators can be a fantastic help.
There are some methods for doing leg curls, but I will show you
the way to do this workout without exercise equipment.
Phen375 could be the strongest along with the safest diet pill on earth, which is made up of unique along with the highest quality
constituents fabricated inside FDA-regulated laboratory in California.


Also visit my website :: phentermine 37.5

Anonymous said...

I want to to thank you for this excellent read!! I definitely loved every bit of it.
I have you bookmarked to look at new things you post…

Check out my blog post; luxury outdoor furniture

Anonymous said...

Hi there just wanted to give you a brief heads up and let you know a
few of the pictures aren't loading properly. I'm not sure why but
I think its a linking issue. I've tried it in two different internet browsers and both show the same results.

Feel free to visit my weblog windows xp registry cleaner

Anonymous said...

Hi, i read your blog from time to time and i own a similar
one and i was just curious if you get a lot of spam
feedback? If so how do you prevent it, any plugin or anything you can suggest?
I get so much lately it's driving me mad so any support is very much appreciated.

Also visit my web site ... airplane landing games

Anonymous said...

Terrific work! That is the type of info that should
be shared across the net. Shame on the search engines for not positioning this submit upper!
Come on over and talk over with my web site . Thanks =)

Feel free to surf to my web site ford ranger

Anonymous said...

Excellent website you have here but I was curious if you knew of any user discussion forums that
cover the same topics talked about in this article?
I'd really love to be a part of community where I can get feed-back from other experienced individuals that share the same interest. If you have any recommendations, please let me know. Thanks!

Review my homepage ... landing page

Anonymous said...

S Green Building Experience. Insurance is a must-have for
a home builders in tennessee's contract. It is funny to think about it carefully. The work is usually awarded to the lowest bidder. Initial step would be determining what kind of requirements you will have all the experience about where everything such as pipes, wires, etc.

Have a look at my page - home builders tn

Anonymous said...

We're a group of volunteers and opening a new scheme in our community. Your website provided us with valuable info to work on. You've done an impressive job and our whole community will be thankful to you.


Also visit my web blog ... bmr calculator for women

Anonymous said...

Heya! I realize this is somewhat off-topic however I had to ask.
Does running a well-established blog such as yours take
a massive amount work? I am brand new to blogging however I do write in my journal on a daily basis.
I'd like to start a blog so I can easily share my personal experience and views online. Please let me know if you have any suggestions or tips for brand new aspiring bloggers. Appreciate it!

my blog post How to get rid of stretch marks

Anonymous said...

I need to to thank you for this very good read!! I certainly loved every little bit of it.

I have got you book-marked to check out new things you post…

my blog post; bankruptcy laws in florida

Anonymous said...

A person necessarily lend a hand to make seriously articles I might state.
This is the very first time I frequented your website page and so far?
I amazed with the analysis you made to make this particular post extraordinary.
Great task!

Feel free to surf to my homepage how to get rid of stretch marks

Anonymous said...

Hurrah, that's what I was exploring for, what a stuff! present here at this website, thanks admin of this web page.

My webpage Bmi Calculator

Anonymous said...

Hi there! I simply would like to offer you a huge thumbs up for the excellent info
you've got right here on this post. I'll be coming back to your web
site for more soon.

Stop by my web site ... diet plans that work

Anonymous said...

I've been exploring for a bit for any high quality articles or weblog posts in this sort of space . Exploring in Yahoo I finally stumbled upon this web site. Studying this info So i'm satisfied to show that I've an incredibly just right uncanny feeling I came upon just what I needed. I most surely will make certain to do not fail to remember this site and provides it a glance on a relentless basis.

My web page - www.oxygenforbusiness.com

Anonymous said...

I'm gone to tell my little brother, that he should also visit this web site on regular basis to get updated from latest news update.

Here is my web page; private sex Chat

Anonymous said...

hey there and thank you for your info – I have definitely
picked up something new from right here. I did however expertise several
technical issues using this site, since I experienced
to reload the site a lot of times previous to I could get it
to load correctly. I had been wondering if your web host is OK?
Not that I'm complaining, but sluggish loading instances times will sometimes affect your placement in google and can damage your quality score if advertising and marketing with Adwords. Well I'm adding this
RSS to my e-mail and could look out for a lot more of your respective exciting
content. Make sure you update this again soon.

Check out my blog post; naija.fm

Anonymous said...

Simply want to say your article is as amazing. The clarity on your
publish is simply nice and that i can assume you are knowledgeable on this
subject. Well along with your permission allow me to grasp
your feed to keep updated with impending post.
Thank you a million and please keep up the enjoyable work.

Feel free to surf to my web site; Www.omni-chat.com

Anonymous said...

constantly i used to read smaller articles or reviews which also clear their motive, and that is also
happening with this piece of writing which I am reading at this place.


Here is my web blog ... http://www.restoredinc.com/member/565779

Anonymous said...

I would like to thank you for the efforts you've put in penning this blog. I really hope to check out the same high-grade blog posts by you in the future as well. In truth, your creative writing abilities has encouraged me to get my own, personal blog now ;)

My webpage: live sexfree

Anonymous said...

Good post. I definitely love this site. Continue the good work!



Here is my blog post free online cam

Anonymous said...

I do not leave a response, however after
browsing a few of the remarks on this page "Routing protocols".
I actually do have a few questions for you if you do not mind.
Is it just me or does it look like a few of the remarks look as if they are left by brain dead visitors?

:-P And, if you are posting on other online sites, I'd like to keep up with anything new you have to post. Would you post a list of all of your shared pages like your twitter feed, Facebook page or linkedin profile?

my homepage: my sex cams

Anonymous said...

I’m not that much of a online reader to be honest but your blogs really nice,
keep it up! I'll go ahead and bookmark your website to come back in the future. All the best

my webpage; web cam porn

Anonymous said...

Hi there, this weekend is pleasant in favor of me, since this moment i
am reading this fantastic educational article here at my house.



My web page: http://elmomah.com

Anonymous said...

Good post. I learn something totally new and challenging
on blogs I stumbleupon every day. It will
always be useful to read content from other writers and practice a little
something from their web sites.

Feel free to visit my web page ... video chat

Anonymous said...

It's a pity you don't have a donate button! I'd certainly donate to this excellent blog! I guess for now i'll settle for bookmarking and adding your RSS feed to my Google account.
I look forward to new updates and will talk about this site with my Facebook group.
Talk soon!

my web blog; live chat sex cam

Anonymous said...

It is really a nice and helpful piece of info. I'm glad that you shared this useful info with us. Please keep us up to date like this. Thanks for sharing.

Here is my web page ... live sex texting

Anonymous said...

Howdy would you mind stating which blog platform you're working with? I'm looking to start
my own blog in the near future but I'm having a hard time deciding between BlogEngine/Wordpress/B2evolution and Drupal. The reason I ask is because your design and style seems different then most blogs and I'm looking for something completely unique.

P.S Sorry for being off-topic but I had to ask!


Feel free to surf to my blog: free chat cam

Anonymous said...

Hello every one, here every one is sharing these kinds of know-how,
therefore it's nice to read this webpage, and I used to go to see this webpage every day.

Feel free to visit my weblog - dimattinacoffee.com.au

Anonymous said...

Pretty! This has been an incredibly wonderful article.
Thanks for providing these details.

Visit my homepage: live sex on stage Video

Anonymous said...

I do not know if it's just me or if perhaps everyone else experiencing issues with your site. It appears as if some of the written text in your posts are running off the screen. Can someone else please comment and let me know if this is happening to them as well? This might be a problem with my internet browser because I've had this happen before.

Kudos

My blog - girl cam chats

Anonymous said...

Wow, marvelous blog layout! How long have you been blogging for?
you made blogging look easy. The overall look of your website is wonderful, as well as
the content!

My webpage :: porncams live

Anonymous said...

This website was... how do you say it? Relevant!! Finally I've found something that helped me. Thanks!

My web site :: sex girl cams

Anonymous said...

Thank you for the good writeup. It in fact was a amusement
account it. Look advanced to far added agreeable from you!
By the way, how can we communicate?

Visit my homepage - live webcams porn free

Anonymous said...

It's amazing to pay a visit this site and reading the views of all friends regarding this post, while I am also zealous of getting know-how.

my web page www.beenpaid.com

Anonymous said...

I simply could not go away your web site
before suggesting that I really enjoyed the standard info a person supply
to your visitors? Is going to be back continuously to check up on new posts

Also visit my blog post free porn videos on porn hub

Anonymous said...

Great article. I will be going through some of these
issues as well..

my web blog :: sex webcam live

Anonymous said...

Superb blog! Do you have any suggestions for aspiring writers?
I'm planning to start my own blog soon but I'm a little lost on
everything. Would you suggest starting with a free platform like Wordpress or go for
a paid option? There are so many choices out there that I'm completely overwhelmed .. Any suggestions? Thank you!

Here is my blog post ... http://www.enstarz.com/

Anonymous said...

Way cool! Some extremely valid points! I appreciate you penning this article and also the rest of the website is really good.


Feel free to visit my web-site: live strip tease - http://movie-links.org/test/social/index.php?do=/blog/7609/what-sort-of-live-porn-cam-chat-babes-you-will-get -

Anonymous said...

Wonderful goods from you, man. I have understand your
stuff previous to and you are just too magnificent.
I really like what you've acquired here, really like what you are stating and the way in which you say it. You make it enjoyable and you still care for to keep it sensible. I can not wait to read far more from you. This is actually a great website.

My blog post private porn chats

Anonymous said...

Someone necessarily lend a hand to make severely posts I might
state. That is the very first time I frequented your website page and to this
point? I surprised with the research you made to make this particular publish amazing.
Fantastic process!

Here is my web site chat free sex cams

Anonymous said...

Hey there are using Wordpress for your blog platform? I'm new to the blog world but I'm trying to
get started and create my own. Do you require any html coding expertise to make your own blog?
Any help would be really appreciated!

Also visit my website; live chat xxx

Anonymous said...

Hi there, i read your blog from time to time and i own
a similar one and i was just curious if you get a lot of spam remarks?
If so how do you prevent it, any plugin or anything you can recommend?
I get so much lately it's driving me crazy so any support is very much appreciated.

Here is my web site; free nude adult chat ()

Anonymous said...

Spot on with this write-up, I seriously think this website needs
a great deal more attention. I'll probably be back again to see more, thanks for the info!

My site :: mature live porn

Anonymous said...

Post writing is also a fun, if you be acquainted with then you can write or else it is difficult to write.


Take a look at my web site; live porn cam chat (www.fish-games.org)

Anonymous said...

It's a pity you don't have a donate button! I'd without a doubt donate to this brilliant blog! I suppose for now i'll settle for bookmarking and
adding your RSS feed to my Google account.

I look forward to brand new updates and will share this website with my Facebook group.
Talk soon!

Feel free to visit my blog: live web cams

Anonymous said...

After I initially left a comment I appear to have clicked on the
-Notify me when new comments are added- checkbox and now whenever a comment is added I receive four
emails with the same comment. Perhaps there is a way you are able to
remove me from that service? Appreciate it!

my blog ... live free sex shows

Anonymous said...

I'm not sure why but this web site is loading very slow for me. Is anyone else having this issue or is it a problem on my end? I'll check back later on and see if the problem still exists.


Stop by my page ... sex chat with webcam

Anonymous said...

It's fantastic that you are getting thoughts from this piece of writing as well as from our discussion made here.

Have a look at my blog: live cams and free chat

Anonymous said...

Great post. I was checking continuously this blog and I'm impressed! Very helpful info specially the last part :) I care for such information much. I was seeking this certain info for a very long time. Thank you and best of luck.

Review my blog post - free nude live cams - Www.marsa-net.com -

Anonymous said...

My relatives always say that I am wasting my time here at
net, except I know I am getting experience every day by reading such fastidious posts.



My web blog - live free porn videos

Anonymous said...

Great article, just what I needed.

Also visit my website - live webcam sex

Smed malak said...

All Over Printed r.i.p shirts and Photo t-shirts - www.tshirtkings247.com customize yours today... 9376034494

alexwat31 said...

such a great post I like Computer Network post and blog also I daily find like that otherwise, I want to show off about Affordable homeowners insurance near me in Floirda just visit here