topic = IP the internet protocol
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| IP datagram format diagram | slide 43
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| what is an IP address | 32-bit identifier associated with each host or router interface
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| what is an interface | connection between host/router and physical link
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| can routers have multiple interfaces | yes
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| how many interfaces does a host have | one or two interfaces (wired ethernet / wireless)
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| what is a subnet | device interfaces that can physically reach each other without passing through anintervening router
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| what are the two IP addresses structures | subnet part and host part
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| what is a subnet part | devices in same subnet have common high order bits
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| what is a host part | remaining low order bits
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| 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
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| what does CIDR stand for | classless interdomain routing
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| 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
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| 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
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| what is a IPv4 subnet mask | 32 bit sequence of ones followed by a block of zeros
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| what do ones in IPv4 subnet mask designate | the network prefix
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| what do zeros in IPv4 subnet mask designate | the host identifier
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| what do we use in shorthand | /24
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| what does /24 mean | means subnet mask has 24 ones and the rest are zeros
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| how does a host get an IP address | it's hard-coded by sysadmin in config file
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| what does DHCP stand for | dynamic host configuration protocol
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| what is the function of DHCP | dynamically get address from as server (plug-and-play)
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| 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)
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| 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
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| example of DHCP client-server scenario | slide 54-55
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| 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)
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| example of DHCP | slide 57-58
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| 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
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| 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
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| what are the two approaches to subnetting | fixed length subnet mask (FLSM) and variable-length subnet mask (VLSM)
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| describe FLSM subnetting | all subnets are equal in size with an equal number of host identifiers
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| 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
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| how is VSLM efficient | it makes more efficient use of given IP address range (default standard for how every network is designed today)
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| what is VSLM supported by | supported by most used protocols on the internet
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| what are some protocols that support VSLM | open shortest path first / enhanced interior gateway protocol / border gateway protocol...
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| 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)
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| in FLSM how does a network get subnet part of IP address | gets allocated portion of its provider ISP' address space
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| example of ISP allocates out its address | slide 62
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| problem exercise | slid 63
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| how to solve the solution use subnet mask table | slide 64-69
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| what is a routing table | summary of all known networks
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| how do routers find the shortest path | routers share routing tables to find new paths and locate the best paths to destinations
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| 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
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| 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
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| what does hierarchical addressing allow | allows for efficient advertisement of routing information
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| hierarchical addressing example | slide 72-73
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| how does an ISP get blocked of addresses | ICANN - internet corporation for assigned names and numbers
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| what does ICANN help with | allocates IP addresses, through 5 regional registries (RR) / manages DNS root zone, including delegation of individual TLD
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| what does ICANN allocate | allocates last chunk of IPv4 addresses to RRs in 2011
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| what's the purpose of NAT | helps IPv4 address space exhaustion
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| how many bit space does IPv6 have | 128-bit address space
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| what does NAT stand for | network address translation
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| what is NAT used for | all devices in local network share just one IPv4 address as far as outside world is concerned
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| 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
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| 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
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| another advantage of NAT | security = devices inside local net not directly addressable, visible by outside world
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| 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#)
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| what do remote clients and servers do when NAT is implemented | they respond using NAT IP address, new port# as destination address
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| what happens in a NAT translation table | every source IP address, new port# to NAT IP address, new port# translation pair
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| 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
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| 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
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| why is NAT here to stay | extensively used in home and institutional nets 4G/5G cellular nets
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| what is the initial motivation for IPv6 | 32-bit IPv4 address space would be completely allocated
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| what are two other additional motivations for IPv6 | speed processing/forwarding = 40-byte fixed length header / enable different network-layer treatment of flows
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| what's the priority of a IPv6 datagram | identify priority among datagrams in flow
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| what is a flow label in an IPv6 datagram | identify datagrams in flow (concept of flow not well defined)
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| how many bits does the source and destination address in IPv6 datagram | 128-bit
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| 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)
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| how will network operate with mixed IPv4 and IPv6 routers | tunneling
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| what's tunneling | IPv6 datagram carried as payload in IPv4 datagram among IPv4 routers (packet within a packet)
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| where is tunneling extensively used | 4G/5G
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| what can't all routers do | can't be upgraded simultaneously from IPv4 to IPv6
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| IPv4 network connection two IPv6 routers diagram | slide 84-87 (IPv4 = root)
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| where is IPv6 adopted from | google = 30% of clients access services via IPv6 / NIST = 1/3 of all US government domains are IPv6 capable
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| 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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