Google Chrome

Google Chrome

Google takes aim squarely at Microsoft with the release of its new Web browser, Chrome. And Microsoft should be very afraid: Chrome lives up to its hype by rethinking the Web browser in clever and convenient ways that make using the Web a more organic experience than you'd get with either Microsoft's Internet Explorer 8 or Mozilla's Firefox 3.

Initially available for download for Windows Vista and XP, Google plans to expand its Chrome offerings to the Mac and Linux platforms as well. The company doesn't offer any timeline for these versions, though..

Chrome automatically detects the Web browser you're using and prompts you through the process of installation (right down to telling you how to access downloaded files within Firefox, for example). When you first run the application, Chrome imports your bookmarks, passwords, and settings from Firefox or Internet Explorer. It even can grab username and password data, and it automatically populates those fields for you when you use Chrome for the first time to visit a particular site

After running through a quick import checklist, Chrome opens on your desktop--and right away you begin to experience the Web in a new way. Chrome's layout is very simple: You'll see a row of tabs running along the top, a Web address bar, and a bookmarks bar that runs beneath the address bar. A separate recent bookmarks box appears at the right of the screen, as does a history search field.

Like its Google stablemates, Chrome has a remarkably minimalist interface. There is no full-scale menu bar and no title bar--and few distractions. All controls are buried beneath two icons to the right of the Omnibar (as Google refers to its address bar): a page icon for managing tabs and using Google Gears to create application-like shortcuts from your desktop to a Web site; and a wrench for history, downloads, and other browser options.

On the Google Blog, Sundar Pichai and Linus Upson acknowledge they pressed the “send” button a day early, tipping off Philipp Lenssen in Germany, who set the fuse on the worldwide blog bomb. At the same time, Google coined a new PR move: announcements in e-comic book form.
You can check that out for in-depth descriptions, explanations, and philosophy behind Google’s new browser—but fair warning it will take a while. Bloggers immediately labeled it an assault on Microsoft, both on the browser level and, in an interesting stretch, the OS level. They wonder, too, about how this will affect Google’s relationship with Mozilla.
It’ll launch at some point today at Google.com/chrome.

First the specs:

• Like Android, Google Chrome is based on, built from the ground up with, open source application framework WebKit; it is intended to be next-generation built for handling Web applications rather than Web pages. It includes Google Gears built-in.
• To that end, Google built its own JavaScript engine, V8, to power web applications with multi-threaded efficiency.
• Browser tabs get their own process rather than tabs sharing processes to solve the ever-dreaded freeze-and-crash problem by freeing up memory and reducing memory fragmentation.
• Each tab has its own URL box, effectively making each tab a browser window
• No about:blank pages. Chrome defaults to a page featuring the four most used search engines and the user’s nine most visited Web pages.
• Similar to IE 8, Chrome has an “Incognito” mode to erase browser history when the browser is closed—something Firefox 3 didn’t include.
• Chrome can be “streamlined” so that the toolbar and URL box are hidden and only the webpage is shown on the screen.
• Chrome features browser extensions allowing it to make hybrid apps similar to Adobe AIR
• An Opera-like dashboard start page and auto-completion.
• It’s pretty strong on the security front. Chrome sandboxes Webpages, preventing drive-by downloads and installations. It continuously makes contact with Google to update a list of known malware sites in order to warn the user.

No word yet on how much the browser actually communicates with Google. Given Google’s history of watching everything its product users do, it wouldn’t be surprising if Google would gather browsing information to use for its search and ad-serving algorithms.
The browser will launch in more than 100 countries today. The company says the launch will add value for the user while driving innovation on the Web. Available only for Windows for now, Google plans to release versions for Mac and Linux as well.

Google has produced an excellent browser that is friendly enough to handle average browsing activities without complicating the tasks, but at the same time it's powerful enough to meet the needs of more-advanced users. The search functionality of the Omnibar is one of many innovations that caught my attention. PC World has chosen to rate this beta version of Chrome because of Google's history of leaving products and services in long-term beta and in an ongoing state of evolution. In the past there has been some speculation that Google would develop their own operating system, but I think Chrome's launch makes one thing is clear: The Web browser is Google's operating system.

DOWNLOAD GOOGLE CHROME

OSPF LSA: OSPF LSA Types | Link-State Advertisement Basics

OSPF LSA: OSPF LSA Types | Link-State Advertisement Basics

Author: - Amarjit Singh

NOTE: Help has been taken from Internet and various books.

NOTE: Type 6 is used for group membership in Multicast OSPF (MOSPF), which is not implemented by Cisco. Type 8 is unused, and Types 9–11 are used for Opaque LSA, which is not used for route calculation but is used for MPLS traffic engineering.

Each LSA has a 20-byte common LSA header, the format for which is illustrated in below Figure

Common LSA Header Format

The list that follows describes the fields in the LSA header

LS Age— gives the time, in seconds, since the LSA originated. The maximum age of the LSA is 3600 seconds; the refresh time is 1800 seconds. If the LS age reaches 3600 seconds, the LSA must be removed from the database.

Options— discussed earlier in “OSPF Key Points Master Document“

LS Type— represents the types of LSA

Link-State ID— Identifies the portion of the network that is being described by the LSA. This field changes according to the LS type

Advertising Router— Represents the router ID of the router originating the LSA.

LS Sequence Number— Detects old or duplicate LSAs. The maximum sequence number is represented by 0x7FFFFFFF. The first sequence number is always 0x80000001. The sequence number 0x80000000 is reserved.

LS Checksum— Performs checksum on the LSA, not including LS age. An LSA can be corrupted during flooding or while kept in the memory, so this checksum is necessary. This field cannot have a value of 0 because 0 means that the checksum has not been performed. The checksum is performed at the time of LSA generation or when the LSA is received. It is also performed every CheckAge interval, which, by default, is 10 minutes.

Length— Includes the length of the LSA, including the 20-byte header

Types of LSA

Type	LSA	Functionality
1	Router	Defines the state and cost of the link to the neighbor and IP prefix associated with the point-to-point link.
2	Network	Defines the number of routers attached to the segment. It gives information about the subnet mask on that segment.
3	Summary network	Describes the destination outside an area but within the OSPF domain. The summary for one area is flooded into other areas, and vice versa.
4	Summary ASBR	Describes the information about the ASBR. In a single area, there will be no summary Type 4 LSA.
5	External	Defines routes to destination external to OSPF domain. Every subnet is represented by a single external LSA.
6	Group membership
7	NSSA	Defines routes to an external destination, but in a separate LSA format known as Type 7.
8	Unused
9-11	Opaque

Router LSA

Router LSAs are generated by each router for each area to which the router belongs.

flooded only within a particular area, because every single router in OSPF would have to carry huge amounts of detailed information

The router indicates whether it's an ABR, ASBR, or an endpoint of a virtual link

Router LSA Packet Format

Bit V— This bit is used to determine whether it's an endpoint of a virtual link.

Bit E— This bit is used to determine whether this router is an Autonomous System Boundary Router (ASBR).

Bit B— This bit is used to determine whether this router is an Area Border Router (ABR).

Number of Links— This includes the number of router links. Note that the router LSA includes all the router links in a single LSA for an area.

Link ID, Link Data, and Type— The Type field represents the four types of router links. The other two fields, Link ID and Link Data, represent the 4-byte IP address value, depending on the network type. One thing to note here is that there can be two types of point-to-point links, numbered and unnumbered. In case of numbered point-to-point links, the Link Data field contains the interface address that connects to the neighbor. In the case of unnumbered links, the Link Data field contains the MIBII Ifindex value, a unique value that is associated with every interface.

ToS and ToS Metric— These fields represents the type of service and are normally set to 0

Metric— This field contains the OSPF cost of a specific link. The formula to calculate OSPF cost is 10⁸/Link bandwidth

Different Router Link Types

Type	Description	Link ID	Link Data
1	Point-to-point numbered	Neighbor's router ID	Interface IP address
1	Point-to-point unnumbered	Neighbor's router ID	MIBII IfIndex value
2	Transit	IP address of the DR	Interface IP address
3	Stub	IP network number	Subnet mask
4	Virtual link	Neighbor's router ID	Interface IP address

Network LSA

The DR generates the network LSA. If no DR exist (for example, in point-to-point or point-to-multipoint networks), there will be no network LSA. The network LSA describes all the routers attached to the network

Network LSA Packet Format

Network Mask— This field indicates the network mask associated with the transit link.

Attached Router— This field includes the router ID of each router associated with this transit link. The designated router also lists itself in attached routers.

Summary LSA

The summary LSA describes the destination outside the area, but still within the AS.

Summary LSAs are generated when there is more than one area provided and Area 0 is configured

The purpose of the summary LSA is to send the reduced topological information outside the area

This LSA does not carry any topological information; it carries only an IP prefix. This LSA is originated by the ABR, as follows:

• From a nonbackbone to a backbone area, summary LSAs are generated for:

- Connected routes

- Intra-area routes

NOTE:

Only intra-area routes are advertised into the backbone to avoid loops. If there are any inter-area routes coming from nonbackbone area it means that the backbone is discontiguous. A discontiguous backbone is not allowed in OSPF network

• From a backbone to a nonbackbone area, summary LSAs are generated for the following:

- Connected routes

- Intra-area routes

- Interarea routes

Two types of summary LSAs exist:

• Type 3— Used for the information about the network
• Type 4— Used for the information about the ASBR

Summary LSA Packet Format

Network Mask— For the Type 3 summary LSA, this field contains the network mask associated with the network. For the Type 4 summary LSA, this field must be 0

Metric— This field represents the cost of the network.

ToS and ToS Metric— These fields are normally set to 0.

Both the Type 3 and Type 4 summary LSAs use the same packet format. The important things to remember about summary LSA Types 3 and 4 are as follows:

• The network mask in Type 3 contains the subnet mask value of the network.
• The network mask field must be 0.0.0.0 in Type 4 LSAs.
• In Type 3 LSAs, the Link-State ID field should have the network number.
• In Type 4 LSAs, the Link-State ID field should have the router ID of the ASBR.
• The advertising router field must contain the router ID of the ABR generating the summary LSA. This is true for both Type 3 and 4 LSAs.

There is one special case of summary LSAs—in cases when a stub-area ABR generates a summary default route. In this case, the Link-State ID field as well as the network mask must be 0.0.0.0

External LSA

The external LSA defines routes to destinations external to the autonomous system Domain-wide, the default route can also be injected as an external route

External LSAs are flooded throughout the OSPF domain, except to stubby areas

To install an external LSA in the routing table, two essential things must take place:

• The calculating router must see the ASBR through the intra-area or interarea route. This means that it should have either a router LSA for the ASBR or a Type 4 LSA for the ASBR, in case of multiple areas.
• The forwarding address must be known through an intra- or interarea route.

External LSA Packet Format

Network Mask— Specifies the network mask of the external network.

Bit E— Specifies the external type. If set, it is an external Type 2; otherwise, it is Type 1. The difference between type and type external is that the Type 1 metric is similar to the OSPF metric and the cost gets changed every hop; in Type 2, however, the external metric doesn't change. The metric remains the same throughout the OSPF domain

Forwarding Address— Indicates the address to which data traffic to the advertised network should be forwarded. If the value is set to 0.0.0.0, this means that the traffic should be forwarded to the ASBR. In some situations, the forwarding address will be nonzero, to avoid suboptimal routing. The following list describes events that will produce a nonzero forwarding address:

• OSPF is enabled on the ASBR's next-hop interface.
• The ASBR's next-hop interface is nonpassive to OSPF.
• The ASBR's next-hop interface network type is not point-to-point or point-to-multipoint.
• The ASBR's next-hop interface address falls into the OSPF network range.

External Route Tag— Not used by OSPF.

External LSA Output

RouterE#show ip ospf database external 10.10.10.0

LS age: 954

Options: (No TOS-capability, DC)

LS Type: AS External Link

Link State ID: 10.10.10.0 (External Network Number)

Advertising Router: 141.108.1.21

LS Seq Number: 80000003

Checksum: 0x97D8

Length: 36

Network Mask: /24

Metric Type: 2 (Larger than any link state path)

TOS: 0

Metric: 20

Forward Address: 0.0.0.0

External Route Tag: 0

This is a Type 2 external LSA. There are a few important things to remember here:

• The Link-State ID field represents the external network number.
• The advertising router field contains the router ID of the ASBR.
• Metric Type: 2 means that the metric—20, in this case—remains the same throughout the OSPF domain.
• A forwarding address of 0.0.0.0 means that the traffic should be forwarded directly to the ASBR.
• The route to the nonzero forwarding address must be known through an intra-area or interarea route; otherwise, the external route will not get installed in the routing table.

You can catch me on mail@amarjit.info

What is OSPF Routing Protocol? OSPF Hidden FACTS Revealed

What is OSPF Routing Protocol? OSPF Hidden FACTS Revealed 

Author: - Amarjit Singh

Why are loopbacks advertised as /32 host routes in OSPF? Loopbacks are considered host routes in OSPF, and they are advertised as /32. If the ip ospf network point−to−point command is configured under loopbacks, OSPF advertises the loopback subnet as the actual subnet configured on loopbacks

All the OSPF packet types share a common 20-byte OSPF protocol header.

Common OSPF Protocol Header Format is as shown below

The current version number of OSPF is 2. Version 1 is not compatible with Version 2

The router ID is used to uniquely identify the router throughout the autonomous system. After the router ID is chosen, it will not change unless the router is restarted, the inter-face that is selected as a router ID is shut down, or the IP address has been removed or replaced on that interface

The value of Area ID must be the same on both sides to form neighbor relationships. There are two ways to write this: Area 1 or Area 0.0.0.1. There is no difference between the two

 The type code for the authentication:

- 0 means that there is a null authentication

- 1 means that the authentication type is plain text

- 2 means that the authentication type is MD5

Hello packets are the first type of packets in OSPF

Hello Packet Format is as shown below

Hello packets are used to form a neighbor relationship between two routers. In environments that include broadcast/nonbroadcast media, Hello packets are used to elect the designated (DR) and backup designated (BDR) routers. On broadcast media, the destination address of the Hello packets is 224.0.0.5. On nonbroadcast media, the destination address is unicast

The network mask is checked only on broadcast media

Hello interval must be the same for the two routers that are trying to form an adjacency. The Hello interval is 10 seconds on broadcast and point-to-point media, and 30 seconds on all other media

 Optional capabilities supported by the router are as follows:

E, when set, means that external LSA are allowed in this area

MC designates multicast OSPF

N/P is used for not-so-stubby area (NSSA) option

EA is the external attribute

O bit is used for opaque LSAs

By default router's priority value is set to 1. A higher priority increases the chances that the router will become the DR. A priority of 0 means that this router will not take part in DR election

By default, the dead interval is four times the Hello interval

The DR is elected through the Hello protocol. If there is no DR, this field has a value of 0.0.0.0. No DRs/BDRs exist on point-to-point or point-to-multipoint segments

The second type of OSPF packet is database description (DBD) packet. The first DBD packet is used to elect the master and slave relationship and to set the initial sequence number elected by the master. The router with the highest router ID becomes the master and initiates the database synchronization. The master sends the sequence number, and the slave acknowledges it.

Database Description Packet Format is as shown below

 Interface MTU contains the largest data size, in bytes, that can be sending through the associated interface. This field must be set to 0 when sending the packet over a virtual link

MS Bit is used for master and slave. When this bit is set, it means that the router is a master in the DBD exchange process. If this bit is set to 0, it means that the router is the slave.

Only a master can increment the sequence number

The Type 3 OSPF packet is a link-state request packet. It is sent if part of the database is missing or out-of-date

Link-State Request Packet Format is as shown below:

OSF packet Type 4 is the link-state update packet, and it implements flooding. Several LSAs are included in a single packet. Link-state update packets are also sent in response to link-state request packets

If an LSA is not acknowledged, it is retransmitted every retransmit interval (5 seconds, by default)

The last type of OSPF packet is the link-state acknowledgment packet, is used to acknowledge each LSA. Multiple LSAs can be acknowledged in a single link-state acknowledgment packet. This packet is responsible for the reliable delivery of link-state update packets

Link-state acknowledgment packets are sent as multicasts. If the state of the router is DR or BDR, the acknowledgment is sent to the OSPF router multicast address of 224.0.0.5. If the state of the router is not DR or BDR, the acknowledgment is sent to the all DR router multicast address of 224.0.0.6

Configure OSPF without AREA 0: CCNP OSPF Case Study

Case Study: - Running OSPF without AREA 0

Author: - Amarjit Singh

Document Type: - Informational

Introduction

Topology used is as shown below

3 Routers are connected with ABR on 3 different AREA’s as shown in above topology diagram.

ABR Router connectivity summary:

Interface	IP Address	OSPF AREA	Remote Connected Router
Interface F0/0	1.1.1.1/30	Area 1	AREA-1
Interface S1/0	2.2.2.1/30	Area 2	AREA-2
Interface E2/0	3.3.3.1/30	Area 3	AREA-3
Interface E2/1	4.4.4.1/24	Reserved for Area 0	AREA-4

Now without configuring AREA 0, no OSPF routes are showing in the routing table. Only direct connected routed are available in the routing table as shown below.

FIGURE 1

FIGURE 2

Also from routers at Area 1, Area 2 & Area 3 only directly connected IP’s are pinging.

FIGURE 3

Now let’s have a look after configuring AREA 0 at ABR. Here I am configuring the IP address 4.4.4.1/24 on the Interface E2/1 in OSPF Area 0 (Refer to ABR Router connectivity summary table)

FIGURE 4

And output of “show ip ospf databse” on ABR before (FIGURE 5) and after (FIGURE 6) configuring AREA 0

FIGURE 5

FIGURE 6

SUMMARY

OSPF will not run without AREA 0. We must have to configure "AREA 0" to run the OSPF. No OSPF routes will be shown in "show ip route". Reason behind this is, each area has its own link state databases which will be shared with AREA 0 only by default. And AREA 0 will then flood the IA routes to other AREA's.

Exception: If using only one area say area 11 and no other area is there then no need to create AREA0

It means to flood LSA 1 and LSA 2, no need to create area 0, but for all other LSA's to be flooded properly, say LSA 3, LSA 4, LSA 5 & LSA 7 AREA 0 is must.

I want to bring one more thing in your notice... and its amazing.... Without creating AREA 0 on ABR, the output of the command "show ip ospf neig" is

ABR#sh ip ospf nei
Neighbor ID Pri State Dead Time Address Interface
10.10.10.2 1 FULL/DR 00:00:39 1.1.1.2 FastEthernet0/
0
10.10.10.3 0 FULL/ - 00:00:37 2.2.2.2 Serial1/0
10.10.10.4 1 FULL/DR 00:00:37 3.3.3.2 Ethernet2/0

Here the interesting thing is "FULL" state. It means if the neighbor ship is in "FULL" state and if OSPF routes are not showing in the routing tabe, then you are not connected with AREA 0. SIMPLE...

The router which is calling as ABR actually is not an ABR. Because ABR is that router whose one leg is connected in area 0. So it clears in my scenario that no area 0 is used then no ABR is present. If no ABR is present then no LSA will be flooded (except LSA1 & LSA2).

In my scenario, the router in multiple areas would know all the destinations (subnets in various areas), but would not propagate them between the areas (as it's not an ABR). Therefore, a router residing solely in area 1 would not receive subnets from area 2 and would not be able to communicate with another router that resides solely in area 2.

Configuration of ABR:

!

version 12.4

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname ABR

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5

!

!

ip cef

!

!

!

!

!

!

!

interface Loopback0

ip address 10.10.10.1 255.255.255.255

!

interface FastEthernet0/0

ip address 1.1.1.1 255.255.255.252

duplex auto

speed auto

!

interface Serial1/0

ip address 2.2.2.1 255.255.255.252

serial restart-delay 0

!

interface Serial1/1

no ip address

shutdown

serial restart-delay 0

!

interface Serial1/2

no ip address

shutdown

serial restart-delay 0

!

interface Serial1/3

no ip address

shutdown

serial restart-delay 0

!

interface Ethernet2/0

ip address 3.3.3.1 255.255.255.252

half-duplex

!

interface Ethernet2/1

ip address 4.4.4.1 255.255.255.0

half-duplex

!

interface Ethernet2/2

no ip address

shutdown

half-duplex

!

interface Ethernet2/3

no ip address

shutdown

half-duplex

!

router ospf 1

log-adjacency-changes

network 1.1.1.0 0.0.0.3 area 1

network 2.2.2.0 0.0.0.3 area 2

network 3.3.3.0 0.0.0.3 area 3

network 4.4.4.0 0.0.0.255 area 0

!

ip http server

!

!

!

!

control-plane

!

banner motd

---

***********************

* *

*THIS IS ABR ROUTER*

***********************

---

!

line con 0

password cisco123

login

line aux 0

line vty 0 4

password cisco123

login

!

!

end