Closed Bolt, simulated KRISS System delayed-blowback
Accessory rails
Let me start off by saying that this guns quality and detailed design
are amazing. I have played airsoft for a few years now, mainly using
AEG. This is my first GBB rifle ( had plenty of pistols). I did alot
of research on this weapon before my purchase. There are a number of
reviews on youtube. and they all pretty much hit the nail on the head. I
have yet to chrono my new baby, but just by shooting it i know that it
has at least the power advertised.
Comparison of the Excel Lookup, Vlookup and Hlookup Functions
The Excel lookup functions - Lookup, Vlookup and Hlookup - are three of the most useful functions supplied by Excel. However, many users get these functions (particularly the Lookup and Vlookup functions) mixed up, and as a result, find that their function doesn't work as expected.
This article aims to clarify the difference between the Excel Lookup, Vlookup and Hlookup functions, and to provide an overview of each of these functions.
All three functions - the Lookup, Vlookup and Hlookup - look up a value in a list and return the corresponding value in a second list. However, each of the functions is designed to work slightly differently.
One of the main considerations when selecting a lookup function is whether your data is organised along rows (i.e. horizontally) or down columns (i.e. vertically). If organised horizontally, you can use either the Hlookup function or Lookup function, and if your data is organised vertically, you can use either the Vlookup function or the Lookup function.
It is also important to consider what you need to happen if the function fails to find an exact match to your lookup value. If you only want to return a value if an exact match is found, and if not, you want an error message to be returned, you will need to use the Vlookup or the Hlookup function (with the range_lookup argument set to FALSE). However, if you want to accept the closest match to your lookup value, any of the three lookup functions can be used to do this.
The three functions (including the two different forms of the Lookup function) are summarised below:
Lookup Function
Vector Form: The vector form of the Excel Lookup function uses two vectors (i.e. Two one-dimensional arrays). As these two vectors are supplied to the function as separate arguments they can be horizontal or vertical, and there are no limitations on their positions in relation to each other.
Array Form: The array form of the Excel Lookup function uses a 2-dimensional array. The first column or row of the array is searched for the lookup value and the value returned is taken from the last column or row. Therefore, this function relies on the data being organised in a table, and the column or row containing the values to be returned must after (but not necessarily adjacent to) the column or row being searched.
Both forms of the Lookup function search for a closest match. I.e. If an exact match to the lookup value is not found, the closest match below the lookup value is used instead.
Vlookup Function
The Excel Vlookup function uses a 2-dimensional array with the data organised in columns. The first column of the array is searched for the lookup value and the user specifies which column the value returned is to be taken from. Therefore, similar to the array form of the Lookup function, the column containing the values to be returned must be to the right of the column to be searched.
The main difference between the Vlookup function and the array form of the Lookup function is that the Vlookup function can be set (via the range_lookup argument) to only return a value if it finds an exact match. However, by default (i.e. If the range_lookup argument is not supplied) the Vlookup function will, like the Lookup function, return the closest match below the lookup value.
Hlookup Function
The Excel Hlookup is the horizontal version of the Vlookup function. The function uses a 2-dimensional array, with the data arranged in rows. The first row of the array is searched for the lookup value and the user specifies which row the value returned is to be taken from. Therefore, in the Hlookup function, the row containing the values to be returned must be below (but not necessarily adjacent to) the searched row.
Also, like the Vlookup function, the Hlookup function uses the range_lookup argument, which allows the user to specify how the function behaves if it fails to find an exact match. If this argument is set to FALSE, the Hlookup function only returns a value if it finds an exact match to the lookup value. However, by default (i.e. If the range_lookup argument is not supplied or is set to TRUE), the Hlookup function will return use the closest match below the lookup value.
It is important to note that in all of the above functions, if you are not requesting an exact match to your lookup value, the data in the column or row to be searched must be sorted into ascending order. If it isn't, this could cause your function to return unexpected results.
Comparison of the Excel Lookup, Vlookup and Hlookup Functions
Vector
Comparison of the Excel Lookup, Vlookup and Hlookup Functions
Comparison of the Excel Lookup, Vlookup and Hlookup Functions Comparison of the Excel Lookup, Vlookup and Hlookup Functions
Vector
Comparison of the Excel Lookup, Vlookup and Hlookup Functions
Comparison of the Excel Lookup, Vlookup and Hlookup Functions
In this paper I will explain many different routing protocols and give some
basic details and features about them. This paper in no way should be considered
a source of full detail about any of the listed protocols. For detailed
information about routing protocols I would suggest looking into the Request For
Comments (RFC) for that protocol, goggling them, or maybe visiting different
vendor's websites such as Cisco, Juniper, or Bay networks. Most vendors' web
sites have detailed explanations about all the Protocols there equipments
support features. Before you can understand routing protocol you will have to
have a basic understanding or IP networks, Variable Length Subnet Masks (VLSM),
Network Topologies (bus, star, Hub, etc..), and the OSI model. If you are not
familiar with any of the above subjects you may want to read up and learn about
them before moving into routing protocols. Routing protocols are what makes the
internet work by moving traffic from network to network. With out routing
protocols the internet could not work because networks would just be separate
LANs with no connection to others LANs. The internet in basic terms is just a
lot of LANs wired together to make a huge WAN.
Protocol types:
Distance Vector: distance vector routing is a type of
routing protocol that discovers routes on interconnected networks. The Distance
Vector routing algorithm is the based on the Bellman-Ford algorithm. Examples of
distance-vector routing protocols include RIP (Routing Information Protocol),
Cisco's IGRP (Internet Gateway Routing Protocol) try Google to see all the
different protocols in the Distance Vector family. Distance Vector protocols are
suitable for smaller networks as many of the protocols in this family aren't
scalable in lager complex networks as they are limited. The main limit to
Distance Vector Protocols is there method that requires each router simply
inform its neighbors of its routing table. This routing table update to other
members is bandwidth intensive to lager networks.
RIP (Routing Information Protocol):
Routing Information Protocol (RIP) is one of the first protocols to be used in
networking and is classified as a distance vector routing protocol. RIP uses
broadcast User Datagram Protocol (UDP) data packets to exchange routing
information. There are two versions RIP V1 & V2. RIP Version 1 is the original
version and has many limitations. The metric that RIP uses to rate the value of
different routes is hop count. The hop count metric works by assigning static
routes with a value of 0 and all other routers values are set by the number of
hops (up to 15) that the data must travel though to get to an end point. RIP
Version 2 supports plain text and MD5 authentication, route summarization,
classless inter-domain routing (CIDR), variable-length subnet masks (VLSMs),
Multicast support. Some vendors support other non-standard features for RIP but
be careful as many vendor centric features are not compatible in a mixed vendor
network.
IGRP (Inter Gateway Routing Protocol):
Interior Gateway Routing Protocol (IGRP) is a distance vector routing protocol
which is a proprietary and invented by Cisco. It is used by routers to exchange
routing data within an autonomous system (AS). IGRP supports multiple metrics
for routes, including bandwidth, load, delay and MTU. This improves reliability
over RIP because IGRP uses advanced metrics to compare two routes into a
combined route. The two routes together are combined into a single metric, using
a formula which can be adjusted via command line. The maximum hop count of IGRP
is 255 which is an improvement over RIPs 15 hop max. Keep in mind that IGRP is a
Cisco proprietary protocol and can not be used in a mixed vendor network.
Link State: Link State routing protocol requires each
router (peer) to maintain at least a partial map of the network. When a network
link changes state (up to down, or vice versa), a notification, called a link
state advertisement (LSA) is flooded throughout the network. All the routers
note the change, and recompute their routes accordingly. This method is more
reliable, easier to debug and less bandwidth-intensive than Distance-Vector. It
is also more complex and more compute- and memory-intensive. Link state routing
protocols are found in many lager networks and provide Scalable solutions for
more complex networks.
OSPF (Open Shortest Path First):
Open shortest path first (OSPF) is a link-state routing protocol that calls for
the sending of link-state advertisements (LSAs) to all other routers within the
same hierarchical area or autonomous system (AS). An AS can be divided into a
number of areas, which are groups of contiguous networks and attached hosts.
Information on attached interfaces, metrics used, and other variables are
included in OSPF LSAs. As OSPF routers accumulate link-state information, they
use the SPF algorithm to calculate the shortest path to each node.
Intermediate System-to-Intermediate System (IS-IS) is a routing protocol
developed by the ISO and is natively an ISO Connectionless Network Service or
CLNS protocol so it does not use IP to carry routing information messages. It
uses OSI protocols to deliver its packets and establish its adjacencies. IS-IS
has been enhanced to carry IP (Internet Protocol) and this is called Integrated
IS-IS. Integrated IS-IS supports VLSM and converges rapidly. It is also scalable
to support very large networks and is the key protocol in many larger ISP's.
Hybrid: Hybrid routing Protocols are a combination or
both Distance Vector and Link state protocols and only one protocol fits into
this field. EIGRP is Cisco Systems Proprietary protocol based on their original
IGRP. For more information on Hybrid Protocols look below to the section on "EIGRP".
EIGRP (Enhanced Inter Gateway Routing Protocol):
Enhanced Inter Gateway Routing Protocol (EIGRP) is Cisco Systems Proprietary
protocol based on their original IGRP. EIGRP is a balanced hybrid IP routing
protocol, with optimizations to minimize both the routing instability incurred
after topology changes, as well as the use of bandwidth and processing power in
the router. EIGRP has Protocol-Dependent Modules that can deal with AppleTalk
and IPX as well as IP. The advantage with this is that only one routing process
need run instead of a routing process for each of the protocols. EIGRP provides
loop-free operation and almost instant simultaneous synchronization of routers.
Inter-Autonomous System: Inter-Autonomous System routing protocols are designed
to connect lager networks or Autonomous Systems (AS) together and allow for
muitiple Autonomous Systems to network. One example for the need of an
inter-autonomous system protocol is to connect two or more Internet Service
Providers (ISP) together so there customer can connect to each other. Without
getting in to too much detail both "Link State & Distance Vector" protocols are
considered intra-autonomous system protocols as they are designed to just route
traffic in a singal AS. Inter-Autonomous System protocols main goal is to
propergate the intra-autonomous system information between different autonomous
systems.
BGP4 (Border Gateway Protocol Version 4):
Border Gateway Protocol is the backbone routing protocol for most of the
internet and allows for peering and carrier networks to connect. BGP is
explained as a path vector protocol. With BGP the policy or attributes for
making the actual route selections among the interconnected autonomous systems
is based on Weight ,Local preference, Multi-exit discriminator, Origin, AS path,
Next hop, & Community. BGP information is propagated through the network by
exchanges of BGP messages (4 types: Open, Update, Notification, & Keep Alive)
between peers. Another key feature to BGP is that is supports Classless Inter
Domain Routing (CIDR) with the support of CIDR BGP can reduce the size of the
Internet routing tables. BGP neighbors exchange full routing information when
the TCP (port 179) connection between neighbors is first established. When
changes to the routing table accrue, the BGP routers send to their neighbors
only those routes that have changed. BGP routers do not send periodic routing
updates and advertise only the optimal paths to a destination.
