Itm 440 Paper on Bonjour

ITM 440-­? 540 Introduc0on to Data Networking and the Internet 03/03/12 1 Router Architectures •? There are 3 steps a router must follow to process and forward a packet to the next hop. –? Check an incoming packet for errors and other parameters –? Look up the des0na0on address in a forwarding table to determine the proper output port for the packet –? Send the packet out the port 03/03/12 2 Router like a Train Roundhouse 03/03/12 3 Router Architecture •? Rou0ng can be implemented using soKware based forwarding –? e. g small dsl router, linux box, etc •? Hardware Based –? These are larger routers ith forwarding fabric architectures. •? ISP routers , Internet backbone, etc 03/03/12 4 Basic Hardware Routers •? Routers are very much like computers. –? CPU’s •? Several types used not necessarily as powerful as pc –? NVRAM (Flash Memory) •? Stores router con? gura0ons –? DRAM •? Shared working storage –? ROM •? Bootstrap for router OS 03/03/12 5 03/03/12 6 Larger Internet Routers •? Fundamental principle is that the func0ons of a router can be split into two dis0nct parts –? Rou0ng and control •? Handles protocols, management of router, etc –? Forwarding packets •? Handles actual forwarding f packets •? Many packets go straight through this func0on 03/03/12 7 03/03/12 8 Router Access •? Console Port –? Port for a serial terminal that is the loca0on as the router and is a]ached by a short cable from the serial port on the terminal to the console port on the router (replaced by RJ45) 03/03/12 9 Console Port 03/03/12 10 Router Access •? Auxiliary Port –? Port for a serial communica0on that is a remote loca0on 03/03/12 11 Router Access 03/03/12 12 Router Access •? Network –? Can always be managed over the same network onwhich it is rou0ng packets 03/03/12 13 03/03/12 14 ForwardingTable Lookups •? Longest Match Rule –? Allows a router to determine the best route based on granularity of the masked address. –? Used when a network ID is found to match more than one subnet mask –? The longest match rule is implemented because the longer the mask found, the be]er granularity the router has in exactly de? ning the correct route.

–? It is oKen called the best match or the more speci? c route for a given des0na0on 03/03/12 15 •? Example: •? – Received datagram of 200. 40. 1. 1 •? – Route table lookup found two entries: –? 200. 40.

1. 0/24 –? 200. 40. 0. 0/16 •? – Route would use he 200. 40.

1. 0/24 03/03/12 16 03/03/12 17 Dual Protocol Stacks •? Hosts can have dual protocol stacks –? If the Ethernet type ?eld is 0x800 the packet is hando? to the IPv4 process –? If the Ethernet type ?eld is 0x86DD the packet is handed o? to the IPv6 process 03/03/12 18 03/03/12 19 Tunneling •? Tunneling occurs whenever the normal sequence of encapsula0on headers is violated •? Four types of tunnels –? Host to router –? Put a frame into a frame and violate the normal OSI-­? RM sequence of headers –? Router to router •? Hosts with duel stack capabili0es can tunnel IPv6 packets to a dual tack router that is only reachable over a series IPv4 only device •? Routers with duel stack capability can tunnel IPv6 packets over an IPv4 infrastructure to other routers 20 03/03/12 Tunneling •? Router to host –? Routers with duel stack capabili0es can tunnel IPv6 packets over an IPv4 infrastructure to a duel stack des0na0on host •? Host to Host –? Hosts with duel stack capabili0es can tunnel IPv6 packets over an IPv4 infrastructure to other duel stack IP hosts without an intervening router 03/03/12 21 03/03/12 22 Tunneling •? The ?rst two methods is when an IPv6 packet is sent to a router nd the endpoint of the tunnel is not the same des0na0on •? The last two methods send the encapsulated IPv6 packet directly to the des0na0on host so the IPv4 and IPv6 addresses used correspond to the same host –? The source host or router must have the tunnel’s address con? gured –? This is called con? gured tunneling 03/03/12 23 Automa0c Tunneling •? Does not require special con? gura0on •? Uses a special form of the IPv6 address •? All duel stack IP hosts recognize the format and encapsulate the IPv6 packet inside an IPv4 packet using the embedded IPv4 address, crea0ng an end to end tunnel ? Hosts that only run IPv6 can also duel stack routers to communicate using a special form of the IPv6 03/03/12 24 03/03/12 25 Tunneling Mechanisms •? Manually con? gure tunnels –? De? ned in RFC 2893 and both endpoints of the tunnel must have both IPv4 and IPv6 addresses •? Generic Rou0ng Encapsula0on (GRE) tunnels –? Designed to transport non-­? IP protcols over IP network •? IPv4 compa0ble (6over4) tunnels –? Also de? ned in RFC 2893 these are automa0c tunnels based on IPv4 compa0ble IPv6 addresses using the :: (Pv4 address) form of IPv6 address 03/03/12 26 Tunneling Mechanisms •? 6to4 unnels –? Another form of automa0c tunnel de? ned in RFC 3065. They use and IPv4 embedded in the IPv6 address to iden0fy the tunnel endpoint •? Intra-­? site Automa0c Tunnel Addressing Protcol (ISATAP) –? Mechanism much like 6to4 tunneling but for local site networks. Uses a special pre? x and the IPv4 address to iden0fy the endpoint 03/03/12 27 6to4 and ISATAP tunnel addressing showing how the 128 bits of the IPv6 address Are structured in each case. (a) 6to4 (b) ISATAP 03/03/12 28 Transi0on Considera0ons •? Terminology used for IPv4 to IPv6 transi0on plans for nodes –? IPv4 only node: host or outer that implements only IPv4 –? IPv6/IPv4 (duel) node: A host or router that implements both IPv4 and IPv6 –? IPv6 only node: A host or router that implements only IPv6 –? IPv6 node: A host or router that implements IPv6 –? IPv4 node: A host or router that implements IPv4 •? Includes IPv6 only and duel node 03/03/12 29 •? Includes IPv4 only and duel node Transi0on Considera0ons •? The plan also de? nes three types of addresses –? IPv4 compa0ble IPv6 address •? An address assigned to an IPv6 node that can be used in both IPv6 and IPv4 packets –? IPv4 mapped IPv6 address •? An address mapped o an IPv4 only node represented as an IPv6 address –? IPv6 only address •? An address globally assigned to any IPv4/IPv6 only node 03/03/12 30 Ques0ons 03/03/12 31 03/03/12 32 Q1 •? 1. Which router, based on the architecture in the ?gure, is probably a small site router? Which is probably a large Internet backbone router? •? Although architectures vary, the router with only memory is likely to be a smaller site router.

The router with separate hardware forwarding and control plane is likely the backbone router. 03/03/12 33 Q2 •? 2. Which output interface, based on the rou0ng table shown in he ?gure, will packets arriving from the directly a]ached host for IPv4 address 10. 10. 11. 1 use for forwarding? Assume longest match is used.

•? 64 is 0100 0000, 128 is 1000 0000, and 11 is 0000 1011. All three routes match the ?rst 16 bits. The /18 masks (01 and 10) do not match the address bit pa]ern (00) in posi0ons 17 and 18. So 10.

10. 0. 0/16 is the longest match and the packet will use output interface #1. 03/03/12 34 Q3 •? 3.

Which output interface will packets for 10. 10. 192. 10 use? Assume longest match is used. •? 192 is 1100 0000.

Again, all three routes match the ?rst 16 bits.The /18 masks (01 and 10) do not match the address bit pa]ern (11) in posi0ons 17 and 18. So 10. 10. 0.

0/16 is again the longest match and the packet will use output interface #1. 03/03/12 35 Q4 •? 4. Is 6to4 tunneling automa0c? How many bits will be used for the subnet iden0? er? •? Yes, 6to4 automa0c tunnels are de? ned in RFC 3065. Sixteen bits are used for subnet ID. See Figure 9-­? 9. 03/03/12 36 Q5 •? 5.

Do the routers require IPv6 support to deliver packets between the two hosts? •? No. If IPv6 is not supported on the routers, 6to4 tunneling can be used to deliver packets. 03/03/12 37