Major goals for IPV6
• Support billions of hosts.
• Reduce the size of the routing tables.
• Simplify the protocol, to allow routers to process packets faster.
• Provide better security (authentication and privacy).
• Pay more attention to type of service.
• Aid multicasting by allowing scopes to be specified.
• Make it possible for a host to roam without changing its address.
• Allow the protocol to evolve in the future.
• Permit the old and new protocols to coexist for years
The Network Layer in the Internet: IPv6
• In 1990, IETF started work on a new version of IP.
• IETF issued a call for proposals and discussion in RFC 1550(IP: Next Generation (IPng) White Paper
Solicitation).
• 21 in 1990 7 in 1992 3 in 1993 1
• IPv6 meets the goals fairly well.
– IPv6 has longer addresses than IPv4. They are 16 bytes long.
– The simplification of the header.
– Better support for options.
– Security
– More attention has been paid to type of service than in the past.
The Network Layer in the Internet: IPv6
The IPv6 fixed header (required).
The Network Layer in the Internet: IPv6
IPv6 extension headers.
The Network Layer in the Internet: IPv6
The hop-by-hop extension header for large datagrams (jumbograms).
The Network Layer in the Internet: IPv6
IPv6 extension headers.
The Network Layer in the Internet: IPv6
Controversies
• Address length: 8 byte, 16 byte, 20 bytes 16bytes
• Hop limit: 8 bits or more 8 bits
• Maximum packet size: 64 KB or larger normal 64kB and permit jumbograms.
• Checksum: needed or not not needed any more.
• Mobile support: yes or no no but.
• Security: yes or no no but.
• Huitema, C. 1998. “IPv6: The New Internet Protocol”
Prentice-Hall.
The Network Layer in the Internet:
Internet Control Protocols: ICMP
The principal ICMP message types.
The Network Layer in the Internet:
Internet Control Protocols: ARP
Two switched Ethernet LANs joined by a router
The Network Layer in the Internet:
Internet Control Protocols: ARP
How does a user on host 1 send a packet to a user on host 2?
• Find the IP address for host 2 (e.g. DNS)
• Build a packet with 192.31.65.5 in the Destination address field
• Find the destination's Ethernet address: Conf File or ARP
• Build an Ethernet frame addressed to E2 and dump it into the Ethernet.
• The Ethernet board of host 2 detects this frame, recognizes it as a frame for itself, and causes an interrupt.
• The Ethernet driver extracts the IP packet from the payload and passes it to the IP software.
The Network Layer in the Internet:
Internet Control Protocols: ARP
How host 1 sends a packet to host 4 (192.31.63.8).
• Host 1 packets the IP packet and sends the frame to E3.
• When the CS router gets the Ethernet frame, it finds the physical address E3 by ARP. It then inserts the packet into the payload field of a frame addressed to E6 and puts it on the net.
• When the Ethernet frame arrives at host 4, the packet is extracted from the frame and passed to the IP software for processing.
The Network Layer in the Internet:
Internet Control Protocols: DHCP
• ARP (Address Resolution Protocol, 地址辨析协议)
• RARP (Reverse Address Resolution Protocol，反向地 址辨析协议)：Given a Link address, what is the
corresponding IP address?
• BOOTP (Bootstrap Protocol) is better than RARP, can be forwarded by a router.
• DHCP (Dynamic Host Configuration Protocol, 动态主 机配置协议) allows both manual IP address assignment and automatic assignment.
The Network Layer in the Internet:
Internet Control Protocols: DHCP
Operation of DHCP.
The Network Layer in the Internet:
Label Switching and MPLS Transmitting a TCP segment
using IP, MPLS, and PPP
The Network Layer in the Internet:
Label Switching and MPLS Forwarding an IP packet through an MPLS network
The Network Layer in the Internet:
OSPF – An Interior Gateway Routing Protocol
• The internet is made up of a large number of autonomous systems.
• A routing algorithm within an AS is called an interior gateway protocol
– Distance vector protocol (Routing Information Protocol)
– Link state protocol (1979)
– OSPF (Open Shortest Path First in 1990)
• A routing algorithm between ASes is called an exterior gateway protocol
– BGP (Border Gateway Protocol)
The Network Layer in the Internet:
OSPF
Requirements for the new routing algorithms:
1. To be open, hence the "O" in OSPF.
2. To support a variety of distance metrics.
3. To be a dynamic algorithm.
4. To support routing based on type of service.
5. To do load balancing
6. To support hierarchical systems.
7. To support security
8. To support connection to the Internet via a tunnel
The Network Layer in the Internet:
OSPF
An autonomous system
The Network Layer in the Internet:
OSPF
A graph representation of the previous slide.
The Network Layer in the Internet:
OSPF
The relation between ASes, backbones, and areas in OSPF.
The Network Layer in the Internet:
OSPF
How a OSPF router works?
• When a router boots, it sends HELLO messages. From the response, each router learns who its neighbors are.
• Adjacent routers exchange information.
– Each router periodically floods LINK STATE
UPDATE messages to each of its adjacent routers.
These must be acknowledged (LINK STATE ACK).
– Either partner can request link state information from the other one using LINK STATE REQUEST
messages.
– Each router constructs the graph for its area(s) and compute the shortest path.
The Network Layer in the Internet:
OSPF
The five types of OSPF messages.
The Network Layer in the Internet:
BGP – The Exterior Gateway Routing Protocol
• Exterior gateway protocol routers have to worry about politics a great deal.
• Typical policies involve political, security, or economic considerations. A few examples of routing constraints are
1.No commercial traffic for educat. network
2.Never put Iraq on route starting at Pentagon 3.Choose cheaper network
4.Choose better performing network
5.Don’t go from Apple to Google to Apple
The Network Layer in the Internet:
BGP
• BGP routers communicate with each other by establishing TCP connections.
• BGP is fundamentally a distance vector protocol, but quite different from most others such as RIP.
– Each BGP router keeps track of the path used (instead of maintaining just the cost to each destination)
– Each BGP router tells its neighbors the exact path it is using (instead of periodically given each neighbor its estimated cost to each possible destination)
The Network Layer in the Internet:
BGP
Routing policies between four Autonomous Systems
The Network Layer in the Internet:
BGP
Propagation of BGP route advertisements
The Network Layer in the Internet:
Internet Multicasting
• Databases, transmitting stock quotes to multiple
brokers, and handling digital conference telephone calls
• IP supports multicasting, using class D address.
• Two kinds of group addresses are supported: permanent addresses and temporary ones. Some permanent group examples:
– 224.0.0.1: All systems on a LAN – 224.0.0.2: All routers on a LAN
– 224.0.0.5: All OSPF routers on a LAN
– 224.0.0.6: All designated OSPF routers on a LAN – 224.0.0.251: All DNS servers on a LAN
The Network Layer in the Internet:
Internet Multicasting
• Multicasting is implemented by special multicast routers, which may or may not be collocated with the standard
routers.
– About once a minute, each multicast router sends a hardware multicast to the hosts on its LAN asking them to report back on the groups their processes currently belong to.
– Each host sends back responses for all the class D addresses it is interested in.
– This query and response packets use a protocol called IGMP (Internet Group Management Protocol).
• Multicast routing is done using spanning trees.
The Network Layer in the Internet:
Mobile IP
The Network Layer in the Internet:
Mobile IP
• Every site that wants to allow its users to roam has to create a home agent.
• Every site that wants to allow visitors has to create a foreign agent.
• When a mobile host shows up at a foreign site, – it contacts the foreign agent there and register.
– The foreign agent then contacts the user's home agent and gives it a care-of address, normally the foreign agent's own IP address.