csc chp4 flashcards Word Scramble
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| Question | Answer |
| IP datagram format diagram | slide 43 |
| what is an IP address | 32-bit identifier associated with each host or router interface |
| what is an interface | connection between host/router and physical link |
| can routers have multiple interfaces | yes |
| how many interfaces does a host have | one or two interfaces (wired ethernet / wireless) |
| what is a subnet | device interfaces that can physically reach each other without passing through anintervening router |
| what are the two IP addresses structures | subnet part and host part |
| what is a subnet part | devices in same subnet have common high order bits |
| what is a host part | remaining low order bits |
| what is the recipe for defining subnets | detach each interface from its host or router creating islands of isolated networks / each isolated network is called a subnet |
| what does CIDR stand for | classless interdomain routing |
| what is the purpose of a CIDR | subnet portion of address of arbitrary length / address format a.b.c.d/x where x is # bits in subnet portion of address |
| what are subnet mask used for | they are used by a computer to determine if any computer is on the same network or on a different network |
| what is a IPv4 subnet mask | 32 bit sequence of ones followed by a block of zeros |
| what do ones in IPv4 subnet mask designate | the network prefix |
| what do zeros in IPv4 subnet mask designate | the host identifier |
| what do we use in shorthand | /24 |
| what does /24 mean | means subnet mask has 24 ones and the rest are zeros |
| how does a host get an IP address | it's hard-coded by sysadmin in config file |
| what does DHCP stand for | dynamic host configuration protocol |
| what is the function of DHCP | dynamically get address from as server (plug-and-play) |
| what's the goal of DHCP | host dynamically obtains IP address from network server when it joins network (can renew its lease on address in use / allows reuse of addressing / support for mobile users who join and leave network) |
| what is the overview of DHCP | host broadcasts DHCP discover msg / DHCP server responds with DHCP offer / host requests IP address = DHCP request msg / DHCP server sends address = DHCP ack msg |
| example of DHCP client-server scenario | slide 54-55 |
| what more can DHCP return on subnet other than an IP address | address of first-hop router for client / name and IP address of DNS server / network mask (indicating network versus host portion of address) |
| example of DHCP | slide 57-58 |
| what is subnetting | dividing a single large network into multiple small networks known as subnets to help relieve network congestion and improve efficiency in utilizing relatively small network address space available |
| what is supernetting | combing multiple networks into a single large network known as supernets to provide route updates in the most efficient way possible by advertising many routes in one ad instead of individually |
| what are the two approaches to subnetting | fixed length subnet mask (FLSM) and variable-length subnet mask (VLSM) |
| describe FLSM subnetting | all subnets are equal in size with an equal number of host identifiers |
| describe VSLM subnetting | subnet design strategy that allows all subnet masks to have variable sizes / network admin can divide an IP address space into subnets of different sizes and allocate it according to individual needs on network |
| how is VSLM efficient | it makes more efficient use of given IP address range (default standard for how every network is designed today) |
| what is VSLM supported by | supported by most used protocols on the internet |
| what are some protocols that support VSLM | open shortest path first / enhanced interior gateway protocol / border gateway protocol... |
| when do you use the same subnet mask for each subnet | in FLSM and all the subnets have the same number of addresses in them (tends to be the most wasteful because it uses more IP addresses than are necessary) |
| in FLSM how does a network get subnet part of IP address | gets allocated portion of its provider ISP' address space |
| example of ISP allocates out its address | slide 62 |
| problem exercise | slid 63 |
| how to solve the solution use subnet mask table | slide 64-69 |
| what is a routing table | summary of all known networks |
| how do routers find the shortest path | routers share routing tables to find new paths and locate the best paths to destinations |
| where is supernetting used | it's used in hierarchical addressing to simplify or summarize network routing decisions with the goal of min processing overheads when matching routes |
| what happens when there is no supernetting | the router will share all routes from routing tables as they are / with supernetting it will summarize them before sharing which reduces the size of routing updates |
| what does hierarchical addressing allow | allows for efficient advertisement of routing information |
| hierarchical addressing example | slide 72-73 |
| how does an ISP get blocked of addresses | ICANN - internet corporation for assigned names and numbers |
| what does ICANN help with | allocates IP addresses, through 5 regional registries (RR) / manages DNS root zone, including delegation of individual TLD |
| what does ICANN allocate | allocates last chunk of IPv4 addresses to RRs in 2011 |
| what's the purpose of NAT | helps IPv4 address space exhaustion |
| how many bit space does IPv6 have | 128-bit address space |
| what does NAT stand for | network address translation |
| what is NAT used for | all devices in local network share just one IPv4 address as far as outside world is concerned |
| how does NAT work for connected devices | all devices in local network have 32-bit addresses in a private IP address space that can only be used in local network |
| what are some advantages of NAT | just one IP address needed from provider ISP for all devices / can change addresses of host in local network without notifying outside world / can change ISP without changing addresses of devices in local network |
| another advantage of NAT | security = devices inside local net not directly addressable, visible by outside world |
| how do you implement NAT | router must have outgoing datagrams = which replace (source IP address, port#) of every outgoing datagram to (NAT IP address, new port#) |
| what do remote clients and servers do when NAT is implemented | they respond using NAT IP address, new port# as destination address |
| what happens in a NAT translation table | every source IP address, new port# to NAT IP address, new port# translation pair |
| what happens when datagrams are incoming | replace NAT IP address, new port# in destination fields of every incoming datagram with corresponding source IP address, port# stored in NAT table |
| how has NAT been controversial | routers should only process up to layer 3 / address shortage should be solved by IPv6 / violates end-to-end argument / NAT traversal = what if client wants to connect to server behind NAT |
| why is NAT here to stay | extensively used in home and institutional nets 4G/5G cellular nets |
| what is the initial motivation for IPv6 | 32-bit IPv4 address space would be completely allocated |
| what are two other additional motivations for IPv6 | speed processing/forwarding = 40-byte fixed length header / enable different network-layer treatment of flows |
| what's the priority of a IPv6 datagram | identify priority among datagrams in flow |
| what is a flow label in an IPv6 datagram | identify datagrams in flow (concept of flow not well defined) |
| how many bits does the source and destination address in IPv6 datagram | 128-bit |
| what's different with IPv6 compared to IPv4 | no checksum (to speed processing at routers) / no fragmentation/reassembly / no options (available as upper-layer, next-header protocol at router) |
| how will network operate with mixed IPv4 and IPv6 routers | tunneling |
| what's tunneling | IPv6 datagram carried as payload in IPv4 datagram among IPv4 routers (packet within a packet) |
| where is tunneling extensively used | 4G/5G |
| what can't all routers do | can't be upgraded simultaneously from IPv4 to IPv6 |
| IPv4 network connection two IPv6 routers diagram | slide 84-87 (IPv4 = root) |
| where is IPv6 adopted from | google = 30% of clients access services via IPv6 / NIST = 1/3 of all US government domains are IPv6 capable |
| how long has IPv6 been deployed for | 25 years and counting (application-level changes in last 25 years = www, social media, streaming media, gaming, telepresence) |
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