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University of British Columbia CICS 515 (Part 2) Computer Networks Lecture 5b-c – IPv6 and Other Protocols Instructor: Dr. Son T. Vuong Email: [email protected] The World Connected Cics 515 – Summer 2012 © Dr. Son Vuong 1 IPv6 Initial motivation: 32-bit address space soon to be completely allocated. Additional motivation: header format helps speed processing/forwarding header changes to facilitate QoS IPv6 datagram format: fixed-length 40 byte header no fragmentation specified in basic header Cics 515 – Summer 2012 © Dr. Son Vuong 2 IPv6 Header (Cont) Priority: identify priority among datagrams in flow Flow Label: identify datagrams in same “flow.” (concept of“flow” not well defined). Next header: identify upper layer protocol for data Cics 515 – Summer 2012 © Dr. Son Vuong 3 Other Changes from IPv4 Checksum: removed entirely to reduce processing time at each hop Options: allowed, but outside of header, indicated by “Next Header” field ICMPv6: new version of ICMP additional message types, e.g. “Packet Too Big” multicast group management functions Cics 515 – Summer 2012 © Dr. Son Vuong 4 Transition From IPv4 To IPv6 Not all routers can be upgraded simultaneous no “flag days” How will the network operate with mixed IPv4 and IPv6 routers? Tunneling: IPv6 carried as payload in IPv4 datagram among IPv4 routers Cics 515 – Summer 2012 © Dr. Son Vuong 5 Dual IPv6/IPv4 Router Tunneling Logical view: Physical view: Dual IPv6/IPv4 Router A B IPv6 IPv6 A B C IPv6 IPv6 IPv4 Flow: X Src: A Dest: F data A-to-B: IPv6 Cics 515 – Summer 2012 © Dr. Son Vuong E F IPv6 IPv6 D E F IPv4 IPv6 IPv6 tunnel Src:B Dest: E Src:B Dest: E Flow: X Src: A Dest: F Flow: X Src: A Dest: F data data B-to-C: IPv6 inside IPv4 B-to-C: IPv6 inside IPv4 Flow: X Src: A Dest: F data E-to-F: IPv6 6 IPv6 – Peer Instruction – Question 5.2 IPv6 supports the following features: A. 128-bit IP address B. Auto-configuration (plug-and-play) (stateless) as well as dynamic IP address via a DHCPv6 server (stateful) C. More options via extension headers including Jumbogram of greater than 64KB D. Efficient header processing E. All the above F. A, B and C Cics 515 – Summer 2012 © Dr. Son Vuong 7 IPv6 – Peer Instruction – Question 5.3 An IPv6 datagram is 80,000 bytes. What extension header must be used? A. Destination option B. Fragmentation C. Authentication D. Hop-by-hop E. None of the above Cics 515 – Summer 2012 © Dr. Son Vuong 8 IPv6 – Peer Instruction – Question 5.4 The IPv6 jumbogram option gives rise to the following issues: A. Fragmentation B. 16-bit length of UDP C. 16-bit MSS option of TCP D. Checksum calculation E. All of the above F. B and C Cics 515 – Summer 2012 © Dr. Son Vuong 9 Ch 4: Network Layer and Routing The IP Protocol Routing IP Format, Addressing, fragmentation, Internet Control Protocols (ICMP) RIP (Routing Information Protocol) OSPF (Open Shortest Path First) The Interior Gateway Routing Protocol BGP – The Exterior Gateway Routing Protocol IPv6 Internet Multicasting Mobile IP Cics 515 – Summer 2012 © Dr. Son Vuong 10 What have we covered? IPv4, IPv6 What’s next ? Internet Control Message Protocol (ICMP) Address resolution (ARP) Getting (dynamic) addresses (DHCP) DNS Routing protocols (RIP, OSPF, BGP) Cics 515 – Summer 2012 © Dr. Son Vuong 11 University of British Columbia CICS 515 (Part 2) Computer Networks Lecture 5c – ICMP, ARP, DHCP, DNS Instructor: Dr. Son T. Vuong Email: [email protected] The World Connected Cics 515 – Summer 2012 © Dr. Son Vuong 12 Lect. 5c – Other IP protocols ICMP, ARP, DHCP (Sect. 4.4.3, 5.4) DNS (Sect. 2.5 ) Internet Control Message Protocol (ICMP) (Sect 4.4.3) Address Resolution (ARP) (Sect 5.4) Dynamic IP address assignment (DHCP) (Sect 5.4) Domain Name System (DNS) (Sect2.5) Cics 515 – Summer 2012 © Dr. Son Vuong 13 ICMP: Internet Control Message Protocol RFC 792 Used by hosts & routers to communicate network-level information error reporting: unreachable host, network, port, protocol echo request/reply (used by ping) Network-layer “above” IP: ICMP msgs carried in IP datagrams ICMP message: type (1B), code (1B), checksum (2B) plus part of IP datagram causing error (header + first 8 bytes of data) Cics 515 – Summer 2012 © Dr. Son Vuong 14 ICMP datagram structure ICMP msgs carried in IP datagrams ICMP data contains part of IP datagram causing error (IP header + first 8 bytes of data) Cics 515 – Summer 2012 © Dr. Son Vuong 15 ICMP: Internet Control Message Protocol Type 0 3 3 3 3 3 3 4 5 8 9 10 11 12 Code 0 0 1 2 3 6 7 0 0-3 0 0 0 0 0 description echo reply (ping) dest. network unreachable dest host unreachable dest protocol unreachable dest port unreachable dest network unknown dest host unknown source quench (congestion control - not used) redirect a host to a better router echo request (ping) route advertisement router discovery (solicitation) TTL expired bad IP header Cics 515 – Summer 2012 © Dr. Son Vuong 16 “Real” Internet delays and routes What do “real” Internet delay & loss look like? traceroute (tracert) program: provides delay measurement from source to router along endend Internet path towards destination. For all i: sends three UDP packets that will reach router i on path towards destination router i will return packets to sender sender times interval between transmission and reply. 3 probes 3 probes 3 probes Cics 515 – Summer 2012 © Dr. Son Vuong 17 Traceroute and ICMP Source sends series of UDP segments to dest When ICMP message arrives, source calculates RTT First has TTL =1 Traceroute does this 3 times Second has TTL=2, etc. Stopping criterion Unlikely port number When nth datagram arrives to UDP segment eventually arrives at destination host nth router: Router discards datagram Destination returns ICMP “port unreachable” packet (type 3, And sends to source an code 3) ICMP message (type 11, When source gets this ICMP, code 0) stops. Message includes name of router& IP address Cics 515 – Summer 2012 © Dr. Son Vuong 18 Address Resolution Protocol (ARP) How do we convert the IP address of each node (either the destination node, or a router) into the address on the local network? E.g. IP -> Ethernet. Each machine keeps a mapping of IP address to physical addresses in a cache. E.g. cascade.cs.ubc.ca 08:00:20:79:70:f5 dragon.cs.ubc.ca 08:00:09:27:b4:73 etc… What if the mapping isn’t known, or has expired? Send an ARP (Address Resolution Protocol) broadcast message over the network. Cics 515 – Summer 2012 © Dr. Son Vuong 19 ARP Packet Format 0 8 16 Hardware type = 1 HLen = 48 PLen = 32 31 ProtocolType = 0x0800 Operation SourceHardwareAddr (bytes 0-3) SourceHardwareAddr (bytes 4-5) SourceProtocolAddr (bytes 2-3) SourceProtocolAddr (bytes 0-1) TargetHardwareAddr (bytes 0-1) TargetHardwareAddr (bytes 2-5) TargetProtocolAddr (bytes 0-3) Cics 515 – Summer 2012 © Dr. Son Vuong 20 ARP Fields Request format HardwareType - Type of physical network (e.g., Ethernet) ProtocolType - Type of higher layer protocol (e.g., IP) HLEN & PLEN - Length of physical and protocol addresses (measured in bits) Operation - Request for an address, or response to a request. Source/Target Physical/Protocol addresses Cics 515 – Summer 2012 © Dr. Son Vuong 21 ARP Comments An ARP packet sits at the same level in the protocol graph as an IP packet. However ARP service is used by IP; thus ARP can also be viewed as a sublayer below IP. ARP table entries timeout in about 10 minutes Update the ARP table with information about the source when you are the target. Hence, both source/target physical/protocol addresses are in the packet. Cics 515 – Summer 2012 © Dr. Son Vuong 22 Dynamic Host Configuration Protocol (DHCP) How does a host get an IP address? Fixed – assigned Dynamic – changeable: via DHCP why? Cics 515 – Summer 2012 © Dr. Son Vuong 23 Dynamic Host Configuration Protocol (DHCP) DHCP allows config info (IP address etc) stored in DHCP server to be retrieved automatically by each host when booted or connected to network (via broadcast DHCPDiscover message) that is, special IP address 255.255.255.255 ignored by everyone except the DHCP server Cics 515 – Summer 2012 © Dr. Son Vuong 24 DHCP (cont’d) DHCP also allows dynamic assignment of IP addresses to hosts (DHCP server maintains a pool of available IP addresses to lease to host and host need to renew lease periodically). It is not desirable to have a DHCP server on every network – instead, uses a relay agent for each network. Relay agent unicasts DHCP request to server Cics 515 – Summer 2012 © Dr. Son Vuong 25 DHCP with relay agent Unicast to server DHCP relay Other networks DHCP server Broadcast Host Cics 515 – Summer 2012 © Dr. Son Vuong 26 DHCP Packet Format Operation HType HLen Hops Transaction ID (Xid) No. of secs Flags/unused Client IP addr Your IP addr (yiaddr) Server IP addr Gateway IP addr Client hardware addr (chaddr) (16 bytes) Server name (64 bytes) file (128 bytes) options DHCP is derived from an earlier protocol called BOOTP Cics 515 – Summer 2012 © Dr. Son Vuong 27 DHCP (cont’d) Sent using UDP Client puts hardware address in chaddr Server replies with IP address in yiaddr (and other config info, e.g. gateway addr, server IP address, etc) Types of DHCP packets (spec’d as options): Discover, Offer, Request, Decline, Ack, Nack, Release Scalability/manageability -- recurring theme (via relay/proxy) Cics 515 – Summer 2012 © Dr. Son Vuong 28 DHCP Scenario DHCP Client DHCP Server ... ... Cics 515 – Summer 2012 © Dr. Son Vuong 29 Layering Relationships between ICMP, ARP, DHCP and IP, UDP ICMP/IP IP calls ARP/Link(Ethernet) DHCP(BOOTP) / UDP(67/68) (for simple configinfo) DHCP(BOOTP) / TFTP/UDP(69) (to get config file) Cics 515 – Summer 2012 © Dr. Son Vuong 30 DNS: Domain Name System Cics 515 – Summer 2012 © Dr. Son Vuong 31 Chapter 2: Application layer 2.1 Principles of network applications 2.2 Web and HTTP 2.3 FTP 2.4 Electronic Mail SMTP, POP3, IMAP 2.5 DNS 2.6 P2P file sharing 2.7 Socket programming with TCP 2.8 Socket programming with UDP 2.9 Building a Web server Cics 515 – Summer 2012 © Dr. Son Vuong 32 Domain Name System (DNS) Overview What do names do? identify objects help locate objects define membership in a group specify a role convey knowledge of a secret Name space defines set of possible names consists of a set of name to value bindings Cics 515 – Summer 2012 © Dr. Son Vuong 33 Properties Names versus addresses Location transparent versus locationdependent Flat versus hierarchical Global versus local Absolute versus relative By architecture versus by convention Unique versus ambiguous Cics 515 – Summer 2012 © Dr. Son Vuong 34 Examples Hosts cheltenham.cs.princeton.edu 192.12.69.17 80:23:A8:33:5B:9F Files /usr/llp/tmp/foo 192.12.69.17 (server, fileid) Users Larry Peterson Cics 515 – Summer 2012 © Dr. Son Vuong [email protected] 35 Summary of “Naming” or identification Domain name: a name that makes sense to a human -- e.g. “cascade.cs.ubc.ca” IP address: an identifier that makes sense to hosts and routers -- e.g. “142.103.7.7” Physical address: an identifier that makes sense to the interface card -- e.g. “8:0:2b:e4:b1:2” Cics 515 – Summer 2012 © Dr. Son Vuong 36 DNS: Domain Name System People: many identifiers: SSN, name, passport # Internet hosts, routers: IP address (32 bit) used for addressing datagrams “name”, e.g., www.yahoo.com - used by humans Q: map between IP addresses and name ? Cics 515 – Summer 2012 © Dr. Son Vuong Domain Name System: distributed database implemented in hierarchy of many name servers application-layer protocol host, routers, name servers to communicate to resolve names (address/name translation) note: core Internet function, implemented as applicationlayer protocol complexity at network’s “edge” 37 DNS: Domain Name System DNS services Hostname to IP address translation Host aliasing Canonical and alias names Mail server aliasing Load distribution Why not centralize DNS? single point of failure traffic volume distant centralized database Maintenance doesn’t scale! Replicated Web servers: set of IP addresses for one canonical name Cics 515 – Summer 2012 © Dr. Son Vuong 38 Examples (cont) Mailboxes User 2 vuong @ cs.ubc.ca cs.ubc.ca Name server 1 Mail program 142.103.7.51 142.103.7.51 4 3 TCP 142.103.7.51 5 IP Services nearby ps printer with short queue and 2MB Cics 515 – Summer 2012 © Dr. Son Vuong 39 Domain Naming System Hierarchy edu princeton … mit cs com gov cisco … yahoo nasa …nsf mil org arpa …navy acm …ieee net uk fr ee physics ux01 ux04 Name chinstrap.cs.princeton.edu Cics 515 – Summer 2012 © Dr. Son Vuong 40 Distributed, Hierarchical Database Root DNS Servers com DNS servers yahoo.com amazon.com DNS servers DNS servers org DNS servers pbs.org DNS servers edu DNS servers poly.edu DNS servers umass.edu DNS servers Client wants IP for www.amazon.com; 1st approx: Client queries a root server to find com DNS server Client queries com DNS server to get amazon.com DNS server Client queries amazon.com DNS server to get IP address for www.amazon.com Cics 515 – Summer 2012 © Dr. Son Vuong 41 Name Servers Partition hierarchy into zones Root name servers Top Level Domain (TLD) Servers edu princeton … mit cs ee com gov cisco … yahoo nasa … nsf mil org arpa … navy acm … ieee uk fr physics ux01 ux04 net Root Each zone corresponds to an admin authority (implemented by two or more name servers for redundancy) Authoritative Servers CS name server UBC … name server name server … Cisco name server ECE name server Local Name Servers (LNS) Cics 515 – Summer 2012 © Dr. Son Vuong 42 DNS: Root name servers contacted by local name server that can not resolve name root name server: contacts authoritative name server if name mapping not known gets mapping returns mapping to local name server a Verisign, Dulles, VA c Cogent, Herndon, VA (also Los Angeles) d U Maryland College Park, MD k RIPE London (also Amsterdam, Frankfurt) g US DoD Vienna, VA h ARL Aberdeen, MD i Autonomica, Stockholm (plus 3 other locations) j Verisign, ( 11 locations) e NASA Mt View, CA f Internet Software C. Palo Alto, CA m WIDE Tokyo (and 17 other locations) b USC-ISI Marina del Rey, CA l ICANN Los Angeles, CA Cics 515 – Summer 2012 © Dr. Son Vuong 13 root name servers worldwide 43 TLD and Authoritative Servers Top-level domain (TLD) servers: responsible for com, org, net, edu, etc, and all top-level country domains uk, fr, ca, jp. Verisign controls .com and .net TLDs Many companies act as intermediaries Educause for edu TLD Authoritative DNS servers: organization’s DNS servers, providing authoritative hostname to IP mappings for organization’s servers (e.g., Web and mail). Can be maintained by organization or service provider Cics 515 – Summer 2012 © Dr. Son Vuong 44 Local Name Server Does not strictly belong to hierarchy Each ISP (residential ISP, company, university) has one. Also called “default name server” When a host makes a DNS query, query is sent to its local DNS server Acts as a proxy, forwards query into hierarchy. Cics 515 – Summer 2012 © Dr. Son Vuong 45 root DNS server Example: Iterative queries 2 Host at cis.poly.edu wants IP address for gaia.cs.umass.edu 3 TLD DNS server 4 5 iterative query: contacted server replies with name of server to contact “I don’t know this name, but ask this server” local DNS server dns.poly.edu 1 8 requesting host cis.poly.edu 7 6 authoritative DNS server dns.cs.umass.edu gaia.cs.umass.edu Cics 515 – Summer 2012 © Dr. Son Vuong 46 Recursive queries root DNS server recursive query: 2 puts burden of name 7 resolution on contacted name server local DNS server heavy load? dns.poly.edu 1 3 6 TLD DNS server 5 4 8 requesting host cis.poly.edu authoritative DNS server dns.cs.umass.edu gaia.cs.umass.edu Cics 515 – Summer 2012 © Dr. Son Vuong 47 DNS: caching and updating records once (any) name server learns mapping, it caches mapping cache entries timeout (disappear) after some time TLD servers typically cached in local name servers Thus root name servers not often visited update/notify mechanisms under design by IETF RFC 2136 http://www.ietf.org/html.charters/dnsind-charter.html Cics 515 – Summer 2012 © Dr. Son Vuong 48 DNS records DNS: distributed db storing resource records (RR) RR format: (name, value, type, ttl) Type = A name is hostname value is IP address Type = CNAME Type = NS name is domain (e.g. foo.com) value is IP address of authoritative name server for this domain servereast.backup2.ibm.com Cics 515 – Summer 2012 © Dr. Son Vuong name is alias name for some “cannonical” (the real) name www.ibm.com is really value is cannonical name Type = MX value is name of mailserver associated with name 49 Example: Root Server (princeton.edu, cit.princeton.edu, NS, IN) [in the Princeton domain] (cit.princeton.edu, 128.196.128.233, A, IN) (cisco.com, thumper.cisco.com, NS, IN) [in the Cisco domain] (thumper.cisco.com, 128.96.32.20, A, IN) … Cics 515 – Summer 2012 © Dr. Son Vuong 50 Further example: Princeton Server [within Princeton domain] (cs.princeton.edu, optima.cs.princeton.edu, NS, IN) [name server] (optima.cs.princeton.edu, 192.12.69.5, A, IN) (ee.princeton.edu, helios.ee.princeton.edu, NS, IN) [another name server] (helios.ee.princeton.edu, 128.196.28.166, A, IN) (jupiter.physics.princeton.edu, 128.196.4.1, A, IN) (saturn.physics.princeton.edu, 128.196.4.2, A, IN) (mars.physics.princeton.edu, 128.196.4.3, A, IN) (venus.physics.princeton.edu, 128.196.4.4, A, IN) Cics 515 – Summer 2012 © Dr. Son Vuong 51 Further example: CS Server [within the CS domain in the Princeton domain] (cs.princeton.edu, optima.cs.princeton.edu, MX, IN) [mail server] (cheltenham.cs.princeton.edu, 192.12.69.60, A, IN) (che.cs.princeton.edu, cheltenham.cs.princeton.edu, CNAME, IN) [alias/actual] (optima.cs.princeton.edu, 192.12.69.5, A, IN) (opt.cs.princeton.edu, optima.cs.princeton.edu, CNAME, IN) [another alias] (baskerville.cs.princeton.edu, 192.12.69.35, A, IN) (bas.cs.princeton.edu, baskerville.cs.princeton.edu, CNAME, IN) Cics 515 – Summer 2012 © Dr. Son Vuong 52 DNS protocol, messages DNS protocol : query and reply messages, both with same message format msg header identification: 16-bit id for query, reply to query uses same id flags: query or reply recursion desired recursion available reply is authoritative Cics 515 – Summer 2012 © Dr. Son Vuong 53 DNS protocol, messages Name, type fields for a query RRs in reponse to query records for authoritative servers additional “helpful” info that may be used Cics 515 – Summer 2012 © Dr. Son Vuong 54 Inserting records into DNS Example: just created startup “Network Utopia” Register name networkuptopia.com at a registrar (e.g., Network Solutions) Need to provide registrar with names and IP addresses of your authoritative name server (primary and secondary) Registrar inserts two RRs into the com TLD server: (networkutopia.com, dns1.networkutopia.com, NS) (dns1.networkutopia.com, 212.212.212.1, A) Put in authoritative server Type A record for www.networkuptopia.com and Type NS record for networkutopia.com How do people get the IP address of your Web site? Cics 515 – Summer 2012 © Dr. Son Vuong 55 Dig www.telus.ca ;; QUESTION SECTION: ;www.telus.ca. IN A ;; ANSWER SECTION: www.telus.ca. 86400 IN CNAME www.telus.com. www.telus.com. 600 IN A 205.206.163.16 ;; AUTHORITY SECTION: telus.com. 600 IN NS dns1.cidc.telus.com. telus.com. 600 IN NS dns2.cidc.telus.com. ;; ADDITIONAL SECTION: dns1.cidc.telus.com. 59695 IN A 216.123.224.131 dns2.cidc.telus.com. 59695 IN A 66.203.199.203 DNS DDoS, Poisoning and Hijacking Cics 515 – Summer 2012 © Dr. Son Vuong 56 Layering Relationships between ICMP, ARP, DHCP, DNS and IP, UDP ICMP/IP, ICMPv6/IPv6 IP calls ARP/Link(Ethernet) DHCP(BOOTP) / UDP(68) (for simple configinfo) DHCP(BOOTP) / TFTP/UDP(69) (to get config file) DNS / UDP(53) Cics 515 – Summer 2012 © Dr. Son Vuong 57 What have we covered? IPv4, IPv6 Internet Control Message Protocol (ICMP) Address resolution (ARP) and getting (dynamic) addresses (DHCP) What’s next ? Routing protocols (RIP, OSPF, BGP) Cics 515 – Summer 2012 © Dr. Son Vuong 58 IPv6 Initial motivation: 32-bit address space soon to be completely allocated. Additional motivation: header format helps speed processing/forwarding header changes to facilitate QoS IPv6 datagram format: fixed-length 40 byte header no fragmentation specified in basic header Cics 515 – Summer 2012 © Dr. Son Vuong 59 IPv6 Header (Cont) Priority: identify priority among datagrams in flow Flow Label: identify datagrams in same “flow.” (concept of“flow” not well defined). Next header: identify upper layer protocol for data Cics 515 – Summer 2012 © Dr. Son Vuong 60 Other Changes from IPv4 Checksum: removed entirely to reduce processing time at each hop Options: allowed, but outside of header, indicated by “Next Header” field ICMPv6: new version of ICMP additional message types, e.g. “Packet Too Big” multicast group management functions Cics 515 – Summer 2012 © Dr. Son Vuong 61 Transition From IPv4 To IPv6 Not all routers can be upgraded simultaneous no “flag days” How will the network operate with mixed IPv4 and IPv6 routers? Tunneling: IPv6 carried as payload in IPv4 datagram among IPv4 routers Cics 515 – Summer 2012 © Dr. Son Vuong 62 Dual IPv6/IPv4 Router Tunneling Logical view: Physical view: Dual IPv6/IPv4 Router A B IPv6 IPv6 A B C IPv6 IPv6 IPv4 Flow: X Src: A Dest: F data A-to-B: IPv6 Cics 515 – Summer 2012 © Dr. Son Vuong E F IPv6 IPv6 D E F IPv4 IPv6 IPv6 tunnel Src:B Dest: E Src:B Dest: E Flow: X Src: A Dest: F Flow: X Src: A Dest: F data data B-to-C: IPv6 inside IPv4 B-to-C: IPv6 inside IPv4 Flow: X Src: A Dest: F data E-to-F: IPv6 63 Ch 4: Network Layer and Routing The IP Protocol Routing IP Format, Addressing, fragmentation, Internet Control Protocols (ICMP) RIP (Routing Information Protocol) OSPF (Open Shortest Path First) The Interior Gateway Routing Protocol BGP – The Exterior Gateway Routing Protocol IPv6 Internet Multicasting Mobile IP Cics 515 – Summer 2012 © Dr. Son Vuong 64 What have we covered? IPv4, IPv6 Internet Control Message Protocol (ICMP) Address resolution (ARP) and getting (dynamic) addresses (DHCP) DNS What’s next ? Routing protocols (RIP, OSPF, BGP) Cics 515 – Summer 2012 © Dr. Son Vuong 65