The Ericsson Certified Associate - IP Networking (ECP-206)

The correct ordering (outer to inner) of packet headers in an IP/MPLS packet is Ethernet, MPLS, IP. An IP/MPLS packet is a packet that is encapsulated with an MPLS label stack between the Ethernet header and the IP header. The Ethernet header contains the source and destination MAC addresses and the EtherType field that indicates the type of the payload. The MPLS label stack contains one or more labels that are used for forwarding decisions by the MPLS routers. Each label consists of four fields: label value, experimental bits, bottom of stack, and time to live. The IP header contains the source and destination IP addresses and other information for routing and fragmentation.  The order of the headers is important because it determines how the packet is processed by different devices in the network 1 2 .

References :  MPLS Label Stack - Cisco ,  MPLS Fundamentals: 3 - MPLS Packet Forwarding

The purpose of the RT attribute is to identify the destination VPN on the egress PE. RT stands for route target, which is a BGP extended community attribute that is used in MPLS VPNs. RT is attached to VPN routes by the ingress PE router and is used to control the import and export of routes between different VPNs.  The egress PE router uses the RT value to determine which VPN routes belong to which VPN customers and installs them in the appropriate VRF table 5 6 .

References :  IP Routing: BGP Configuration Guide - BGP-RT and VPN … - Cisco ,  < rt > : The Ruby Text element - MDN Web Docs

Two statements that are true about the Ericsson Router 6000 series are:

The Router 6000 uses the same building practice and accessories as the Ericsson Radio System. The Ericsson Radio System is a modular and scalable radio access network solution that supports multiple standards, bands, and layers. The Router 6000 series is fully integrated into the Ericsson Radio System, using the same building practice and accessories such as mounting kits, cables, power supplies, etc.  This simplifies installation, operation, and maintenance of both radio and transport equipment 7 8 .

The Router 6000 products range from all-outdoor small site routers to large aggregation routers. The Router 6000 series consists of three main products: the Router 6672 for access, the Router 6675 for pre-aggregation, and the Router 6274 for metro aggregation. The Router 6672 is an all-outdoor small cell site router with high-capacity and low-power consumption. The Router 6675 is a combined access and E-RAN switch with hardware-accelerated IPSec and high-accuracy internal clock.  The Router 6274 is a high-capacity metro aggregation router with SDN functionality and flexible interface options 7 8 .

References :  Router 6000 Series - Ericsson ,  New Ericsson Router 6000 series couples radio and IP transport for 5G future - Global Brands Magazine

Two protocols that apply to both IPv4 and IPv6 are:

SNMP: This stands for Simple Network Management Protocol, which is a protocol that allows network administrators to monitor and manage network devices such as routers, switches, servers, printers, etc. SNMP uses a client-server model, where an SNMP manager (client) can query or configure an SNMP agent (server) on a network device using SNMP messages.  SNMP can operate over both IPv4 and IPv6 networks 5 6 .

DNS: This stands for Domain Name System, which is a protocol that translates human-readable domain names (such as www.example.com) into numerical IP addresses (such as 192.0.2.1 or 2001:db8::1) that identify network devices. DNS uses a hierarchical distributed database of name servers that store and resolve domain names and IP addresses.  DNS can support both IPv4 and IPv6 addresses 7 8 .

References :  Simple Network Management Protocol - Wikipedia ,  SNMP over IPv6 - Cisco ,  Domain Name System - Wikipedia ,  DNS for IPv6 - Cisco

The correct order of DiffServ priority (highest to lowest) for the DiffServ classes: Default Forwarding (DF), Network Control (NC), Assured Forwarding (AF), and Expedited Forwarding (EF) is EF, NC, AF, DF. DiffServ is a QoS model that classifies and prioritizes traffic into different service classes based on the DSCP field in the IP header. The DSCP field is a 6-bit field that can encode up to 64 different per-hop behaviors (PHBs). The DiffServ classes are predefined groups of PHBs that have similar characteristics and requirements. The four main DiffServ classes are:

EF: This class provides the highest priority and lowest delay for real-time applications such as voice and video.  The DSCP value for EF is 101110 or 46 in decimal 1 2 .

NC: This class provides the second highest priority and low delay for network control traffic such as routing protocols and network management.  The DSCP value for NC is 110000 or 48 in decimal 1 2 .

AF: This class provides four levels of assured forwarding with different drop probabilities for each level. AF is suitable for applications that require guaranteed bandwidth and delivery assurance, such as web browsing and email.  The DSCP values for AF range from 001010 to 011110 or 10 to 46 in decimal 1 2 .

DF: This class provides the lowest priority and best-effort service for applications that can tolerate packet loss and delay, such as file transfer and backup.  The DSCP value for DF is 000000 or 0 in decimal 1 2 .

References :  Differentiated Services - Wikipedia ,  DSCP - Differentiated Services Code Point - Mpirical

In the exhibit, the action performed by router R3 for traffic arriving from router R2 towards router R4 is PHP, which stands for penultimate hop popping. PHP is a process in which the penultimate hop router (the router before the egress router) removes the top label from an MPLS packet before forwarding it to the egress router. This reduces the label stack depth of the packet and relieves the egress router from performing a label lookup operation. In the exhibit, router R3 is the penultimate hop for traffic arriving from router R2 towards router R4.  Router R3 will perform a PHP operation, removing the top label from the incoming packet before forwarding it to router R4 7 8 .

References :  PHP Tutorial - W3Schools ,  PHP: Downloads

Peers recognize each other’s ability to use MP-BGP extensions by advertising the ability using the capabilities field during the session establishment. MP-BGP is an extension to BGP that allows BGP to carry routing information for multiple network layer protocols, such as IPv6, VPNv4, multicast, etc. To support MP-BGP, peers need to exchange their capabilities during the session establishment phase, which consists of three steps: open, keepalive, and update. In the open message, peers can include an optional parameter called capabilities, which indicates what kind of address families and subsequent address families they can support.  If both peers agree on a common set of capabilities, they can proceed to exchange routing information for those address families using update messages 5 6 .

References :  Use of MP-BGP Extensions for IPv6 Interdomain Routing ,  MP-EBGP Configuration Example - Cisco

A network operator who wants to make sure voice data is prioritized should assign it to Ethernet traffic class 6. Ethernet traffic class is a term used to refer to the priority code point (PCP) field in the VLAN header of an Ethernet frame. The PCP field is a 3-bit field that can encode up to eight different priority levels, ranging from 0 (lowest) to 7 (highest). The PCP values can be mapped to different types of traffic according to their QoS requirements. The recommended mapping is as follows :

PCP 0: Best effort (default)

PCP 1: Background

PCP 2: Spare

PCP 3: Excellent effort

PCP 4: Controlled load

PCP 5: Video

PCP 6: Voice

PCP 7: Network control

Voice data is a type of real-time traffic that requires the highest priority and lowest delay in the network. Therefore, it should be assigned to PCP 6, which corresponds to Ethernet traffic class 6 .

References : [IEEE 802.1Q - Wikipedia], [What is “link aggregation” and how does it benefit your network? | PC Gamer]

The function of LSR from an LDP perspective is to distribute labels of FEC to its LDP peers. LSR stands for Label Switching Router, which is a router that forwards packets based on labels rather than IP addresses in an MPLS network. LDP stands for Label Distribution Protocol, which is a protocol that distributes labels for MPLS forwarding along the shortest path calculated by an IGP. FEC stands for Forwarding Equivalence Class, which is a group of packets that are forwarded in the same manner by an LSR.  An LSR uses LDP to advertise the label mappings for each FEC to its LDP peers, which are other LSRs that have established an LDP session with it 1 2 .

References :  Ldp | Microsoft Learn ,  Label Distribution Protocol - Wikipedia